1
|
Li Z, Liu J, Rasmita A, Zhang Z, Gao W, Chia EEM. Room-Temperature Geometrical Circular Photocurrent in Few-Layer MoS 2. NANO LETTERS 2024; 24:5952-5957. [PMID: 38726903 DOI: 10.1021/acs.nanolett.4c00057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2024]
Abstract
Valleytronics, i.e., the manipulation of the valley degree of freedom, offers a promising path for energy-efficient electronics. One of the key milestones in this field is the room-temperature manipulation of the valley information in thick-layered material. Using scanning photocurrent microscopy, we achieve this milestone by observing a geometrically dependent circular photocurrent in a few-layer molybdenum disulfide (MoS2) under normal incidence. Such an observation shows that the system symmetry is lower than that of bulk MoS2 material, preserving the optical chirality-valley correspondence. Moreover, the circular photocurrent polarity can be reversed by applying electrical bias. We propose a model where the observed photocurrent results from the symmetry breaking and the built-in field at the electrode-sample interface. Our results show that the valley information is still retained even in thick-layered MoS2 at room temperature and opens up new opportunities for exploiting the valley index through interface engineering in multilayer valleytronics devices.
Collapse
Affiliation(s)
- Ziqi Li
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Jiayun Liu
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Abdullah Rasmita
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Zhaowei Zhang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
- Department of Physics, School of Sciences, Great Bay University, Dongguan 523000, China
- Great Bay Institute for Advanced Study, Dongguan 523000, China
| | - Weibo Gao
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
- The Photonics Institute and Centre for Disruptive Photonic Technologies, Nanyang Technological University, Singapore 637371, Singapore
- Centre for Quantum Technologies, National University of Singapore, Singapore 117543, Singapore
| | - Elbert E M Chia
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| |
Collapse
|
2
|
Strauß F, Zeng Z, Braun K, Scheele M. Toward Gigahertz Photodetection with Transition Metal Dichalcogenides. Acc Chem Res 2024; 57:1488-1499. [PMID: 38713448 DOI: 10.1021/acs.accounts.4c00088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2024]
Abstract
ConspectusTransition metal dichalcogenides (TMDCs) exhibit favorable properties for optical communication in the gigahertz (GHz) regime, such as large mobilities, high extinction coefficients, cheap fabrication, and silicon compatibility. While impressive improvements in their sensitivity have been realized over the past decade, the bandwidths of these devices have been mostly limited to a few megahertz. We argue that this shortcoming originates in the relatively large RC constants of TMDC-based photodetectors, which suffer from high surface defect densities, inefficient charge carrier injection at the electrode/TMDC interface, and long charging times. However, we show in a series of papers that rather simple adjustments in the device architecture afford TMDC-based photodetectors with bandwidths of several hundreds of megahertz. We rationalize the success of these adjustments in terms of the specific physical-chemical properties of TMDCs, namely their anisotropic in-plane/out-of-plane carrier behavior, large optical absorption, and chalcogenide-dependent surface chemistry. Just one surprisingly simple yet effective pathway to fast TMDC photodetection is the reduction of the photoresistance by using light-focusing optics, which enables bandwidths of 0.23 GHz with an energy consumption of only 27 fJ/bit.By reflecting on the ultrafast intrinsic photoresponse times of a few picoseconds in TMDC heterostructures, we motivate the application of more demanding chemical strategies to exploit such ultrafast intrinsic properties for true GHz operation in real devices. A key aspect in this regard is the management of surface defects, which we discuss in terms of its dependence on the layer thickness, its tunability by molecular adlayers, and the prospects of replacing thermally evaporated metal contacts by laser-printed electrodes fabricated with inks of metalloid clusters. We highlight the benefits of combining TMDCs with graphene to heterostructures that exhibit the ultrafast photoresponse and large spectral range of Dirac materials with the low dark currents and high responsivities of semiconductors. We introduce the bulk photovoltaic effect in TMDC-based materials with broken inversion symmetry as well as a combination of TMDCs with plasmonic nanostructures as means for increasing the bandwidth and responsivity simultaneously. Finally, we describe the prospects of embedding TMDC photodetectors into optical cavities with the objective of tuning the lifetime of the photoexcited state and increasing the carrier mobility in the photoactive layer.The findings and concepts detailed in this Account demonstrate that GHz photodetection with TMDCs is feasible, and we hope that these bright prospects for their application as next-generation optoelectronic materials motivate more chemists and material scientists to actively pursue the development of the more complicated material combinations outlined here.
Collapse
Affiliation(s)
- Fabian Strauß
- Institute of Physical and Theoretical Chemistry, Universität Tübingen, Auf der Morgenstelle 18, D-72076 Tübingen, Germany
- Center for Light-Matter Interaction, Sensors & Analytics LISA+, Universität Tübingen, Auf der Morgenstelle 15, D-72076 Tübingen, Germany
| | - Zhouxiaosong Zeng
- Institute of Physical and Theoretical Chemistry, Universität Tübingen, Auf der Morgenstelle 18, D-72076 Tübingen, Germany
| | - Kai Braun
- Institute of Physical and Theoretical Chemistry, Universität Tübingen, Auf der Morgenstelle 18, D-72076 Tübingen, Germany
- Center for Light-Matter Interaction, Sensors & Analytics LISA+, Universität Tübingen, Auf der Morgenstelle 15, D-72076 Tübingen, Germany
| | - Marcus Scheele
- Institute of Physical and Theoretical Chemistry, Universität Tübingen, Auf der Morgenstelle 18, D-72076 Tübingen, Germany
- Center for Light-Matter Interaction, Sensors & Analytics LISA+, Universität Tübingen, Auf der Morgenstelle 15, D-72076 Tübingen, Germany
| |
Collapse
|
3
|
Jeffries WR, Jawaid AM, Vaia RA, Knappenberger KL. Thickness-dependent electronic relaxation dynamics in solution-phase redox-exfoliated MoS2 heterostructures. J Chem Phys 2024; 160:144707. [PMID: 38597312 DOI: 10.1063/5.0200398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Accepted: 03/20/2024] [Indexed: 04/11/2024] Open
Abstract
Electronic relaxation dynamics of solution-phase redox-exfoliated molybdenum disulfide (MoS2) monolayer and multilayer ensembles are described. MoS2 was exfoliated using polyoxometalate (POM) reductants. This process yields a colloidal heterostructure consisting of MoS2 2D sheet multilayers with surface-bound POM complexes. Using two-dimensional electronic spectroscopy, transient bleaching and photoinduced absorption signals were detected at excitation/detection energies of 1.82/1.87 and 1.82/1.80 eV, respectively. Approximate 100-fs bandgap renormalization (BGR) and subsequent defect- and phonon-mediated relaxation on the picosecond timescale were resolved for several MoS2 thicknesses spanning from 1 to 2 L to ∼20 L. BGR rates were independent of sample thickness and slightly slower than observations for chemical vapor deposition-grown MoS2 monolayers. However, defect-mediated relaxation accelerated ∼10-fold with increased sample thicknesses. The relaxation rates increased from 0.33 ± 0.05 to 1.2 ± 0.1 and 3.1 ± 0.4 ps-1 for 1-2 L, 3-4 L, and 20 L fractions. The thicknesses-dependent relaxation rates for POM-MoS2 heterostructures were modeled using a saturating exponential function that showed saturation at thirteen MoS2 layers. The results suggest that the increased POM surface coverage leads to larger defect density in the POM-MoS2 heterostructure. These are the first descriptions of the influence of sample thickness on electronic relaxation rates in solution-phase redox-exfoliated POM-MoS2 heterostructures. Outcomes of this work are expected to impact the development of solution-phase exfoliation of 2D metal-chalcogenide heterostructures.
Collapse
Affiliation(s)
- William R Jeffries
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Ali M Jawaid
- Air Force Research Laboratory, 2941 Hobson Way, Wright Patterson Air Force Base, Dayton, Ohio 45433, USA
| | - Richard A Vaia
- Air Force Research Laboratory, 2941 Hobson Way, Wright Patterson Air Force Base, Dayton, Ohio 45433, USA
| | - Kenneth L Knappenberger
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| |
Collapse
|
4
|
Morabito F, Synnatschke K, Mehew JD, Varghese S, Sayers CJ, Folpini G, Petrozza A, Cerullo G, Tielrooij KJ, Coleman J, Nicolosi V, Gadermaier C. Long lived photogenerated charge carriers in few-layer transition metal dichalcogenides obtained from liquid phase exfoliation. NANOSCALE ADVANCES 2024; 6:1074-1083. [PMID: 38356640 PMCID: PMC10863726 DOI: 10.1039/d3na00862b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2023] [Accepted: 11/26/2023] [Indexed: 02/16/2024]
Abstract
Semiconducting transition metal dichalcogenides are important optoelectronic materials thanks to their intense light-matter interaction and wide selection of fabrication techniques, with potential applications in light harvesting and sensing. Crucially, these applications depend on the lifetimes and recombination dynamics of photogenerated charge carriers, which have primarily been studied in monolayers obtained from labour-intensive mechanical exfoliation or costly chemical vapour deposition. On the other hand, liquid phase exfoliation presents a high throughput and cost-effective method to produce dispersions of mono- and few-layer nanosheets. This approach allows for easy scalability and enables the subsequent processing and formation of macroscopic films directly from the liquid phase. Here, we use transient absorption spectroscopy and spatiotemporally resolved pump-probe microscopy to study the charge carrier dynamics in tiled nanosheet films of MoS2 and WS2 deposited from the liquid phase using an adaptation of the Langmuir-Schaefer technique. We find an efficient photogeneration of charge carriers with lifetimes of several nanoseconds, which we ascribe to stabilisation at nanosheet edges. These findings provide scope for photocatalytic and photodetector applications, where long-lived charge carriers are crucial, and suggest design strategies for photovoltaic devices.
Collapse
Affiliation(s)
- Floriana Morabito
- Area Science Park Basovizza S.S. 14 Km 163.5 34149 Trieste Italy
- Dipartimento di Fisica, Politecnico di Milano Piazza L. da Vinci 32 20133 Milano Italy
- Center for Nano Science and Technology @PoliMi, Istituto Italiano di Tecnologia Via Rubattino 81 20134 Milan Italy
- CNR-IOM, Consiglio Nazionale delle Ricerche Istituto Officina dei Materiali Trieste Italy
| | - Kevin Synnatschke
- School of Physics, CRANN & AMBER Research Centres, Trinity College Dublin Dublin D02 Ireland
| | - Jake Dudley Mehew
- Catalan Institute of Nanoscience and Nanotechnology ICN2 UAB Campus Bellaterra (Barcelona) 08193 Spain
| | - Sebin Varghese
- Catalan Institute of Nanoscience and Nanotechnology ICN2 UAB Campus Bellaterra (Barcelona) 08193 Spain
| | - Charles James Sayers
- Dipartimento di Fisica, Politecnico di Milano Piazza L. da Vinci 32 20133 Milano Italy
| | - Giulia Folpini
- Center for Nano Science and Technology @PoliMi, Istituto Italiano di Tecnologia Via Rubattino 81 20134 Milan Italy
| | - Annamaria Petrozza
- Center for Nano Science and Technology @PoliMi, Istituto Italiano di Tecnologia Via Rubattino 81 20134 Milan Italy
| | - Giulio Cerullo
- Dipartimento di Fisica, Politecnico di Milano Piazza L. da Vinci 32 20133 Milano Italy
| | - Klaas-Jan Tielrooij
- Catalan Institute of Nanoscience and Nanotechnology ICN2 UAB Campus Bellaterra (Barcelona) 08193 Spain
- TU Eindhoven, Department of Applied Physics Den Dolech 2 5612 AZ Eindhoven The Netherlands
| | - Jonathan Coleman
- School of Physics, CRANN & AMBER Research Centres, Trinity College Dublin Dublin D02 Ireland
| | - Valeria Nicolosi
- School of Physics, CRANN & AMBER Research Centres, Trinity College Dublin Dublin D02 Ireland
| | - Christoph Gadermaier
- Dipartimento di Fisica, Politecnico di Milano Piazza L. da Vinci 32 20133 Milano Italy
- Center for Nano Science and Technology @PoliMi, Istituto Italiano di Tecnologia Via Rubattino 81 20134 Milan Italy
| |
Collapse
|
5
|
Boora M, Lin YC, Chen C, Trainor N, Robinson JA, Redwing JM, Suh JY. Low-Frequency Raman Study of Large-Area Twisted Bilayers of WS 2 Stacked by an Etchant-Free Transfer Method. ACS APPLIED MATERIALS & INTERFACES 2024; 16:2902-2911. [PMID: 38166373 DOI: 10.1021/acsami.3c14708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2024]
Abstract
Monolayer transition metal dichalcogenides have strong intracovalent bonding. When stacked in multilayers, however, weak van der Waals interactions dominate interlayer mechanical coupling and, thus, influence their lattice vibrations. This study presents the frequency evolution of interlayer phonons in twisted WS2 bilayers, highly subject to the twist angle. The twist angle between the layers is controlled to modulate the spacing between the layers, which, in turn, affects the interlayer coupling that is probed by Raman spectroscopy. The shifts of high-frequency E2g1 (Γ) and A1g (Γ) phonon modes and their frequency separations are dependent on the twist angle, reflecting the correlation between the interlayer mechanical coupling and twist angle. In this work, we fabricated large-area, twisted bilayer WS2 with a clean interface with controlled twist angles. Polarized Raman spectroscopy identified new interlayer modes, which were not previously reported, depending on the twist angle. The appearance of breathing modes in Raman phonon spectra provides evidence of strong interlayer coupling in bilayer structures. We confirm that the twist angle can alter the exciton and trion dynamics of bilayers as indicated by the photoluminescence peak shift. These large-area controlled twist angle samples have practical applications in optoelectronic device fabrication and twistronics.
Collapse
Affiliation(s)
- Manpreet Boora
- Department of Physics, Michigan Technological University, Houghton, Michigan 49931, United States
| | - Yu-Chuan Lin
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu City 300093, Taiwan
| | - Chen Chen
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Nicholas Trainor
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Joshua A Robinson
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- 2D Crystal Consortium Materials Innovation Platform, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Chemistry and Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Joan M Redwing
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- 2D Crystal Consortium Materials Innovation Platform, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Jae Yong Suh
- Department of Physics, Michigan Technological University, Houghton, Michigan 49931, United States
| |
Collapse
|
6
|
Mao Y, Wang H, Kislyakov I, Wang Z, Dong N, Wang J. Nonlinear optical properties and ultrafast carrier dynamics of ultrathin ReSe 2. OPTICS LETTERS 2023; 48:6259-6262. [PMID: 38039241 DOI: 10.1364/ol.510204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Accepted: 11/12/2023] [Indexed: 12/03/2023]
Abstract
Rhenium diselenide (ReSe2) has shown great application potential in the field of optical devices because of its excellent optoelectronic properties. In this study, we systematically investigated the nonlinear optical absorption properties of mono- and bi-layer ReSe2 and the ultrafast carrier dynamics process in the ultraviolet to near-infrared spectral range as the essential foundational groundwork for harnessing the potential of ultrathin ReSe2-based optoelectronic devices. We found that ReSe2 has excellent nonlinear absorption performance and a low saturation absorption intensity that is better than that of many semiconductor materials. Meanwhile, pump-probe and transient absorption technology revealed the underlying dynamic mechanisms, including bandgap renormalization and Auger recombination. This study can broaden the horizons of material science and propel the development of different applications of ReSe2.
Collapse
|
7
|
Dutta R, Bala A, Sen A, Spinazze MR, Park H, Choi W, Yoon Y, Kim S. Optical Enhancement of Indirect Bandgap 2D Transition Metal Dichalcogenides for Multi-Functional Optoelectronic Sensors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2303272. [PMID: 37453927 DOI: 10.1002/adma.202303272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 06/21/2023] [Accepted: 07/03/2023] [Indexed: 07/18/2023]
Abstract
The unique electrical and optical properties of transition metal dichalcogenides (TMDs) make them attractive nanomaterials for optoelectronic applications, especially optical sensors. However, the optical characteristics of these materials are dependent on the number of layers. Monolayer TMDs have a direct bandgap that provides higher photoresponsivity compared to multilayer TMDs with an indirect bandgap. Nevertheless, multilayer TMDs are more appropriate for various photodetection applications due to their high carrier density, broad spectral response from UV to near-infrared, and ease of large-scale synthesis. Therefore, this review focuses on the modification of the optical properties of devices based on indirect bandgap TMDs and their emerging applications. Several successful developments in optical devices are examined, including band structure engineering, device structure optimization, and heterostructures. Furthermore, it introduces cutting-edge techniques and future directions for optoelectronic devices based on multilayer TMDs.
Collapse
Affiliation(s)
- Riya Dutta
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do, 16419, Republic of Korea
| | - Arindam Bala
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do, 16419, Republic of Korea
| | - Anamika Sen
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do, 16419, Republic of Korea
| | - Michael Ross Spinazze
- Waterloo Institute for Nanotechnology and the Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
| | - Heekyeong Park
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do, 16419, Republic of Korea
| | - Woong Choi
- School of Materials Science & Engineering, Kookmin University, Seoul, 02707, Republic of Korea
| | - Youngki Yoon
- Waterloo Institute for Nanotechnology and the Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
| | - Sunkook Kim
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do, 16419, Republic of Korea
| |
Collapse
|
8
|
Yagodkin D, Kumar A, Ankerhold E, Richter J, Watanabe K, Taniguchi T, Gahl C, Bolotin KI. Probing the Formation of Dark Interlayer Excitons via Ultrafast Photocurrent. NANO LETTERS 2023; 23:9212-9218. [PMID: 37788809 PMCID: PMC10603811 DOI: 10.1021/acs.nanolett.3c01708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 08/15/2023] [Indexed: 10/05/2023]
Abstract
Optically dark excitons determine a wide range of properties of photoexcited semiconductors yet are hard to access via conventional time-resolved spectroscopies. Here, we develop a time-resolved ultrafast photocurrent technique (trPC) to probe the formation dynamics of optically dark excitons. The nonlinear nature of the trPC makes it particularly sensitive to the formation of excitons occurring at the femtosecond time scale after the excitation. As a proof of principle, we extract the interlayer exciton formation time of 0.4 ps at 160 μJ/cm2 fluence in a MoS2/MoSe2 heterostructure and show that this time decreases with fluence. In addition, our approach provides access to the dynamics of carriers and their interlayer transport. Overall, our work establishes trPC as a technique to study dark excitons in various systems that are hard to probe by other approaches.
Collapse
Affiliation(s)
- Denis Yagodkin
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Abhijeet Kumar
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Elias Ankerhold
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Johanna Richter
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Kenji Watanabe
- Research
Center for Functional Materials, National
Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International
Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Cornelius Gahl
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Kirill I. Bolotin
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| |
Collapse
|
9
|
Bae S, Jeong TY, Raebiger H, Yee KJ, Kim YH. Localized coherent phonon generation in monolayer MoSe 2 from ultrafast exciton trapping at shallow traps. NANOSCALE HORIZONS 2023; 8:1282-1287. [PMID: 37470115 DOI: 10.1039/d3nh00194f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/21/2023]
Abstract
We report spectroscopic evidence for the ultrafast trapping of band edge excitons at defects and the subsequent generation of defect-localized coherent phonons (CPs) in monolayer MoSe2. While the photoluminescence measurement provides signals of exciton recombination at both shallow and deep traps, our time-resolved pump-probe spectroscopy on the sub-picosecond time scale detects localized CPs only from the ultrafast exciton trapping at shallow traps. Based on occupation-constrained density functional calculations, we identify the Se vacancy and the oxygen molecule adsorbed on a Se vacancy as the atomistic origins of deep and shallow traps, respectively. Establishing the correlations between the defect-induced ultrafast exciton trapping and the generation of defect-localized CPs, our work could open up new avenues to engineer photoexcited carriers through lattice defects in two-dimensional materials.
Collapse
Affiliation(s)
- Soungmin Bae
- Department of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea.
- Department of Physics, Yokohama National University, Yokohama, Japan
| | - Tae Young Jeong
- Department of Physics, Chungnam National University, Daejeon 34134, Korea.
| | - Hannes Raebiger
- Department of Physics, Yokohama National University, Yokohama, Japan
| | - Ki-Ju Yee
- Department of Physics, Chungnam National University, Daejeon 34134, Korea.
| | - Yong-Hoon Kim
- Department of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea.
| |
Collapse
|
10
|
Ter Huurne SET, van Hoof NJJ, Gómez Rivas J. Thickness-dependent Auger scattering in a single WS 2 microcrystal probed with time-resolved terahertz near-field microscopy. OPTICS LETTERS 2023; 48:708-711. [PMID: 36723569 DOI: 10.1364/ol.477389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Accepted: 12/28/2022] [Indexed: 06/18/2023]
Abstract
Time-resolved terahertz (THz) spectroscopy has been shown as a powerful technique to non-invasively determine the charge carrier properties in photoexcited semiconductors. However, the long wavelengths of terahertz radiation reduce the applicability of this technique to large samples. Using THz near-field microscopy, we show THz measurements of the lifetime of 2D single exfoliated microcrystals of transition metal dichalcogenides (WS2). The increased spatial resolution of THz near-field microscopy allows spatial mapping of the evolution of the carrier lifetime, revealing Auger assisted surface defect recombination as the dominant recombination channel. THz near-field microscopy allows for the non-invasive and high-resolution investigation of material properties of 2D semiconductors relevant for nanoelectronic and optoelectronic applications.
Collapse
|
11
|
Gholipoor M, Solhtalab N, Mohammadi MH. High-performance parallel tandem MoTe2/perovskite solar cell based on reduced graphene oxide as hole transport layer. Sci Rep 2022; 12:20455. [DOI: 10.1038/s41598-022-25015-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 11/23/2022] [Indexed: 11/29/2022] Open
Abstract
AbstractRecently, the impressive achievements accomplished in multijunction (tandem) perovskite solar cells have triggered a huge research effort to boost their performance. Here, using a three-dimensional (3D) finite element method (FEM) technique, we propose and investigate a parallel tandem PSCs consisting of two absorbing layers of MoTe2 and CH3NH3PbI3 with cascaded bandgaps to more efficiently use the near-infrared (NIR) solar spectrum. Endowed with a bandgap of about 1 eV, the MoTe2 layer in conjunction with a CH3NH3PbI3 layer is able to broaden the light absorption range of structure beyond the wavelength of 800 nm, up to 1200 nm. In addition to this, the MoTe2 material can not only appreciably harvest light even with a thickness as low as 20 nm due to their high absorption coefficient, but also make a perfect band alignment with the CH3NH3PbI3 layer. As a result, the proposed multijunction PCS yields a high power conversion efficiency (PCE) of 18.52% with a VOC of 0.83 V, Jsc of 26.25 mA/cm2, and FF of 0.84, which is considerably greater than its corresponding single-junction PSCs with PCE, VOC, Jsc, and FF of, 14.01%, 1.14 V, 15.20 mA/cm2, and 0.81, respectively. Furthermore, to mitigate the VOC loss caused by the low bandgap of MoTe2, we demonstrate an increase in VOC from 0.84 to 0.928 V and in PCE from 18.52% to 20.32%, when we replace a reduced graphene oxide (rGO) layer with Spiro-OMeTAD layer as a hole transport layer (HTL).
Collapse
|
12
|
Wang X, Niu G, Jiang J, Sui L, Zeng X, Liu X, Zhang Y, Wu G, Yuan K, Yang X. Anomalous Dynamics of Defect-Assisted Phonon Recycling in Few-Layer Mo 0.5W 0.5S 2. J Phys Chem Lett 2022; 13:10395-10403. [PMID: 36318176 DOI: 10.1021/acs.jpclett.2c02935] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Alloying has emerged as a new strategy to tune the function of 2D transition metal dichalcogenides (TMDCs). However, the lack of research on the electrical and structural properties of these alloys limits their practical applications. Here, femtosecond transient absorption spectroscopy with pump pulse tunability is performed to elucidate the ultrafast carrier dynamics in the few-layer Mo0.5W0.5S2 prepared by the liquid phase exfoliation method. An anomalous rebleaching of the ground state is observed at high pump fluence by 3.1 eV excitation. We ascribe this rebleaching of the ground state to the mechanism that the carriers trapped in the defect are thermally excited back to the untrapped exciton state due to the phonon recycling, which hinders the dissipation of nonradiative energy, through comparative experiments and global analysis. Our findings demonstrate a novel energy transfer channel assisted by defect in few-layer TMDCs which is critical for their advanced applications.
Collapse
Affiliation(s)
- Xiaowei Wang
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
- University of the Chinese Academy of Sciences, Beijing 100039, China
| | - Guangming Niu
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
- Marine Engineering College, Dalian Maritime University, Dalian 116026, China
| | - Jutao Jiang
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
- University of the Chinese Academy of Sciences, Beijing 100039, China
| | - Laizhi Sui
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
| | - Xiangyu Zeng
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
- Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China
| | - Xin Liu
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
- Science College, Dalian Maritime University, Dalian 116026, China
| | - Yutong Zhang
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
| | - Guorong Wu
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
| | - Kaijun Yuan
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
| | - Xueming Yang
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
- Department of Chemistry, College of Science, Southern University of Science and Technology, Shenzhen 518055, China
| |
Collapse
|
13
|
ter Huurne SE, Da Cruz AR, van Hoof N, Godiksen RH, Elrafei SA, Curto AG, Flatté ME, Rivas JG. High-Frequency Sheet Conductance of Nanolayered WS 2 Crystals for Two-Dimensional Nanodevices. ACS APPLIED NANO MATERIALS 2022; 5:15557-15562. [PMID: 36338326 PMCID: PMC9623546 DOI: 10.1021/acsanm.2c03517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Accepted: 09/29/2022] [Indexed: 06/16/2023]
Abstract
Time-resolved terahertz (THz) spectroscopy is a powerful technique for the determination of charge transport properties in photoexcited semiconductors. However, the relatively long wavelengths of THz radiation and the diffraction limit imposed by optical imaging systems reduce the applicability of THz spectroscopy to large samples with dimensions in the millimeter to centimeter range. Exploiting THz near-field spectroscopy, we present the first time-resolved THz measurements on a single exfoliated 2D nanolayered crystal of a transition metal dichalcogenide (WS2). The high spatial resolution of THz near-field spectroscopy enables mapping of the sheet conductance for an increasing number of atomic layers. The single-crystalline structure of the nanolayered crystal allows for the direct observation of low-energy phonon modes, which are present in all thicknesses, coupling with free carriers. Density functional theory calculations show that the phonon mode corresponds to the breathing mode between atomic layers in the weakly bonded van der Waals layers, which can be strongly influenced by substrate-induced strain. The non-invasive and high-resolution mapping technique of carrier dynamics in nanolayered crystals by time-resolved THz time domain spectroscopy enables possibilities for the investigation of the relation between phonons and charge transport in nanoscale semiconductors for applications in two-dimensional nanodevices.
Collapse
Affiliation(s)
- Stan E.T. ter Huurne
- Department
of Applied Physics and Eindhoven Hendrik Casimir Institute, Eindhoven University of Technology, P.O. Box 513, Eindhoven5600 MB, The Netherlands
| | - Adonai Rodrigues Da Cruz
- Department
of Applied Physics and Eindhoven Hendrik Casimir Institute, Eindhoven University of Technology, P.O. Box 513, Eindhoven5600 MB, The Netherlands
| | - Niels van Hoof
- Department
of Applied Physics and Eindhoven Hendrik Casimir Institute, Eindhoven University of Technology, P.O. Box 513, Eindhoven5600 MB, The Netherlands
| | - Rasmus H. Godiksen
- Department
of Applied Physics and Eindhoven Hendrik Casimir Institute, Eindhoven University of Technology, P.O. Box 513, Eindhoven5600 MB, The Netherlands
| | - Sara A. Elrafei
- Department
of Applied Physics and Eindhoven Hendrik Casimir Institute, Eindhoven University of Technology, P.O. Box 513, Eindhoven5600 MB, The Netherlands
| | - Alberto G. Curto
- Department
of Applied Physics and Eindhoven Hendrik Casimir Institute, Eindhoven University of Technology, P.O. Box 513, Eindhoven5600 MB, The Netherlands
| | - Michael E. Flatté
- Department
of Applied Physics and Eindhoven Hendrik Casimir Institute, Eindhoven University of Technology, P.O. Box 513, Eindhoven5600 MB, The Netherlands
- Department
of Physics and Astronomy, University of
Iowa, Iowa City, Iowa52242, United States
| | - Jaime Gómez Rivas
- Department
of Applied Physics and Eindhoven Hendrik Casimir Institute, Eindhoven University of Technology, P.O. Box 513, Eindhoven5600 MB, The Netherlands
| |
Collapse
|
14
|
Kim S, Yoon S, Ahn H, Jin G, Kim H, Jo MH, Lee C, Kim J, Ryu S. Photoluminescence Path Bifurcations by Spin Flip in Two-Dimensional CrPS 4. ACS NANO 2022; 16:16385-16393. [PMID: 36129115 DOI: 10.1021/acsnano.2c05600] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Ultrathin layered crystals of coordinated chromium(III) are promising not only as two-dimensional (2D) magnets but also as 2D near-infrared (NIR) emitters due to long-range spin correlation and efficient transition between high- and low-spin excited states of Cr3+ ions. In this study, we report on the dual-band NIR photoluminescence (PL) of CrPS4 and show that its excitonic emission bifurcates into fluorescence and phosphorescence depending on thickness, temperature, and defect density. In addition to the spectral branching, the biexponential decay of PL transients, also affected by the three factors, could be well described within a three-level kinetic model for Cr(III). In essence, the PL bifurcations are governed by activated reverse intersystem crossing from the low- to high-spin states, and the transition barrier becomes lower for thinner 2D samples because of surface-localized defects. Our findings can be generalized to 2D solids of coordinated metals and will be valuable in realizing groundbreaking magneto-optic functions and devices.
Collapse
Affiliation(s)
- Suhyeon Kim
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea
| | - Sangho Yoon
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea
- Center for Van der Waals Quantum Solids, Institute for Basic Science (IBS), Pohang 37673, Korea
| | - Hyobin Ahn
- School of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Korea
| | - Gangtae Jin
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea
- Center for Van der Waals Quantum Solids, Institute for Basic Science (IBS), Pohang 37673, Korea
| | - Hyesun Kim
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea
| | - Moon-Ho Jo
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea
- Center for Van der Waals Quantum Solids, Institute for Basic Science (IBS), Pohang 37673, Korea
| | - Changgu Lee
- School of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Korea
| | - Jonghwan Kim
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea
- Center for Van der Waals Quantum Solids, Institute for Basic Science (IBS), Pohang 37673, Korea
| | - Sunmin Ryu
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea
- Institute for Convergence Research and Education in Advanced Technology (I-CREATE), Yonsei University, Seoul 03722, Korea
| |
Collapse
|
15
|
Lu J, Ye Q, Ma C, Zheng Z, Yao J, Yang G. Dielectric Contrast Tailoring for Polarized Photosensitivity toward Multiplexing Optical Communications and Dynamic Encrypt Technology. ACS NANO 2022; 16:12852-12865. [PMID: 35914000 DOI: 10.1021/acsnano.2c05114] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
A selective-area oxidation strategy is developed to polarize high-symmetry 2D layered materials (2DLMs). The dichroic ratio of the derived O-WS2/WS2 photodetector reaches ∼8, which is competitive among state-of-the-art polarization photodetectors. Finite-different time-domain simulations consolidate that the polarization-sensitive photoresponse is associated with anisotropic spacial confinement, which gives rise to distinct dielectric contrasts for linearly polarized light of various directions and thus the polarization-dependent near-field distribution. Furthermore, selective-area oxidation treatment brings about dual effects, comprising the in situ formation of seamless in-plane WS2 homojunctions by thickness tailoring and the formation of out-of-plane O-WS2/WS2 heterojunctions. As a consequence, the recombination of photocarriers is markedly suppressed, resulting in outstanding photosensitivity with the optimized responsivity, external quantum efficiency, and detectivity of 0.161 A/W, 49.4%, and 1.4 × 1011 Jones for an O-WS2/WS2 photodetector in a self-powered mode. A scheme of multiplexing optical communications is revealed by harnessing the intensity and polarization state of light as independent transmission channels. Furthermore, dynamic encryption by leveraging the polarization state as a secret key is proposed. In the end, broad universality is reinforced through the induction of linear dichroism within 2D WSe2 crystals. On the whole, this study provides an additional perspective on polarization optoelectronics based on 2DLMs.
Collapse
Affiliation(s)
- Jianting Lu
- State Key Laboratory of Optoelectronic Materials and Technologies, Nanotechnology Research Center, School of Materials Science & Engineering, Sun Yat-sen University, Guangzhou 510275, Guangdong, P. R. China
| | - Qiaojue Ye
- State Key Laboratory of Optoelectronic Materials and Technologies, Nanotechnology Research Center, School of Materials Science & Engineering, Sun Yat-sen University, Guangzhou 510275, Guangdong, P. R. China
| | - Churong Ma
- Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications, Institute of Photonics Technology, Jinan University, Guangzhou 511443, China
| | - Zhaoqiang Zheng
- School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006, Guangdong, P. R. China
| | - Jiandong Yao
- State Key Laboratory of Optoelectronic Materials and Technologies, Nanotechnology Research Center, School of Materials Science & Engineering, Sun Yat-sen University, Guangzhou 510275, Guangdong, P. R. China
- Guangzhou Key Laboratory of Flexible Electronic Materials and Wearable Devices, Sun Yat-sen University, Guangzhou 510275, Guangdong, P. R. China
| | - Guowei Yang
- State Key Laboratory of Optoelectronic Materials and Technologies, Nanotechnology Research Center, School of Materials Science & Engineering, Sun Yat-sen University, Guangzhou 510275, Guangdong, P. R. China
- Guangzhou Key Laboratory of Flexible Electronic Materials and Wearable Devices, Sun Yat-sen University, Guangzhou 510275, Guangdong, P. R. China
| |
Collapse
|
16
|
Kwon S, Jeong DY, Hong C, Oh S, Song J, Choi SH, Kim KK, Yoon S, Choi T, Yee K, Kim J, You Y, Kim D. Exciton Transfer at Heterointerfaces of MoS 2 Monolayers and Fluorescent Molecular Aggregates. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2201875. [PMID: 35712754 PMCID: PMC9376849 DOI: 10.1002/advs.202201875] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 05/25/2022] [Indexed: 06/15/2023]
Abstract
Integration of distinct materials to form heterostructures enables the proposal of new functional devices based on emergent physical phenomena beyond the properties of the constituent materials. The optical responses and electrical transport characteristics of heterostructures depend on the charge and exciton transfer (CT and ET) at the interfaces, determined by the interfacial energy level alignment. In this work, heterostructures consisting of aggregates of fluorescent molecules (DY1) and 2D semiconductor MoS2 monolayers are fabricated. Photoluminescence spectra of DY1/MoS2 show quenching of the DY1 emission and enhancement of the MoS2 emission, indicating a strong electronic interaction between these two materials. Nanoscopic mappings of the light-induced contact potential difference changes rule out the CT process at the interface. Using femtosecond transient absorption spectroscopy, the rapid interfacial ET process from DY1 aggregates to MoS2 and a fourfold extension of the exciton lifetime in MoS2 are elucidated. These results suggest that the integration of 2D inorganic semiconductors with fluorescent molecules can provide versatile approaches to engineer the physical characteristics of materials for both fundamental studies and novel optoelectronic device applications.
Collapse
Affiliation(s)
- Soyeong Kwon
- Department of PhysicsEwha Womans UniversitySeoul03760Korea
| | - Dong Yeun Jeong
- Division of Chemical Engineering and Materials Scienceand Graduate Program for System Health Science and EngineeringEwha Womans UniversitySeoul03760Korea
| | - Chengyun Hong
- Center for Integrated Nanostructure Physics (CINAP)Institute for Basic Science (IBS)Suwon16419Korea
- Department of Energy ScienceSungkyunkwan UniversitySuwon16419Korea
| | - Saejin Oh
- Center for Integrated Nanostructure Physics (CINAP)Institute for Basic Science (IBS)Suwon16419Korea
- Department of Energy ScienceSungkyunkwan UniversitySuwon16419Korea
| | - Jungeun Song
- Department of PhysicsEwha Womans UniversitySeoul03760Korea
| | - Soo Ho Choi
- Center for Integrated Nanostructure Physics (CINAP)Institute for Basic Science (IBS)Suwon16419Korea
| | - Ki Kang Kim
- Center for Integrated Nanostructure Physics (CINAP)Institute for Basic Science (IBS)Suwon16419Korea
- Department of Energy ScienceSungkyunkwan UniversitySuwon16419Korea
| | - Seokhyun Yoon
- Department of PhysicsEwha Womans UniversitySeoul03760Korea
| | - Taeyoung Choi
- Department of PhysicsEwha Womans UniversitySeoul03760Korea
| | - Ki‐Ju Yee
- Department of PhysicsChungnam National UniversityDaejeon34134Korea
| | - Ji‐Hee Kim
- Center for Integrated Nanostructure Physics (CINAP)Institute for Basic Science (IBS)Suwon16419Korea
- Department of Energy ScienceSungkyunkwan UniversitySuwon16419Korea
| | - Youngmin You
- Division of Chemical Engineering and Materials Scienceand Graduate Program for System Health Science and EngineeringEwha Womans UniversitySeoul03760Korea
| | - Dong‐Wook Kim
- Department of PhysicsEwha Womans UniversitySeoul03760Korea
| |
Collapse
|
17
|
Lyu PT, Li QY, Wu P, Sun C, Kang B, Chen HY, Xu JJ. Decrypting Material Performance by Wide-field Femtosecond Interferometric Imaging of Energy Carrier Evolution. J Am Chem Soc 2022; 144:13928-13937. [PMID: 35866699 DOI: 10.1021/jacs.2c05735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Energy carrier evolution is crucial for material performance. Ultrafast microscopy has been widely applied to visualize the spatiotemporal evolution of energy carriers. However, direct imaging of a small amount of energy carriers on the nanoscale remains difficult due to extremely weak transient signals. Here, we present a method for ultrasensitive and high-throughput imaging of energy carrier evolution in space and time. This method combines femtosecond pump-probe techniques with interferometric scattering microscopy (iSCAT), named Femto-iSCAT. The interferometric principle and unique spatially modulated contrast enhancement enable the exploration of new science. We address three important and challenging problems: transport of different energy carriers at various interfaces, heterogeneous hot-electron distribution and relaxation in single plasmonic resonators, and distinct structure-dependent edge-state dynamics of carriers and excitons in optoelectronic semiconductors. Femto-iSCAT holds great potential as a universal tool for ultrasensitive imaging of energy carrier evolution in space and time.
Collapse
Affiliation(s)
- Pin-Tian Lyu
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Qing-Yue Li
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Pei Wu
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Chao Sun
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Bin Kang
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Hong-Yuan Chen
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Jing-Juan Xu
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| |
Collapse
|
18
|
Maklar J, Stühler R, Dendzik M, Pincelli T, Dong S, Beaulieu S, Neef A, Li G, Wolf M, Ernstorfer R, Claessen R, Rettig L. Ultrafast Momentum-Resolved Hot Electron Dynamics in the Two-Dimensional Topological Insulator Bismuthene. NANO LETTERS 2022; 22:5420-5426. [PMID: 35709372 PMCID: PMC9284614 DOI: 10.1021/acs.nanolett.2c01462] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Two-dimensional quantum spin Hall (QSH) insulators are a promising material class for spintronic applications based on topologically protected spin currents in their edges. Yet, they have not lived up to their technological potential, as experimental realizations are scarce and limited to cryogenic temperatures. These constraints have also severely restricted characterization of their dynamical properties. Here, we report on the electron dynamics of the novel room-temperature QSH candidate bismuthene after photoexcitation using time- and angle-resolved photoemission spectroscopy. We map the transiently occupied conduction band and track the full relaxation pathway of hot photocarriers. Intriguingly, we observe photocarrier lifetimes much shorter than those in conventional semiconductors. This is ascribed to the presence of topological in-gap states already established by local probes. Indeed, we find spectral signatures consistent with these earlier findings. Demonstration of the large band gap and the view into photoelectron dynamics mark a critical step toward optical control of QSH functionalities.
Collapse
Affiliation(s)
- Julian Maklar
- Fritz-Haber-Institut
der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
| | - Raúl Stühler
- Physikalisches
Institut and Würzburg-Dresden Cluster of Excellence ct.qmat, University of Würzburg, D-97070 Würzburg, Germany
| | - Maciej Dendzik
- Fritz-Haber-Institut
der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
| | - Tommaso Pincelli
- Fritz-Haber-Institut
der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
| | - Shuo Dong
- Fritz-Haber-Institut
der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
| | - Samuel Beaulieu
- Fritz-Haber-Institut
der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
| | - Alexander Neef
- Fritz-Haber-Institut
der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
| | - Gang Li
- School
of Physical Science and Technology, ShanghaiTech
University, Shanghai 200031, China
| | - Martin Wolf
- Fritz-Haber-Institut
der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
| | - Ralph Ernstorfer
- Fritz-Haber-Institut
der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
- Institut
für Optik und Atomare Physik, Technische
Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany
| | - Ralph Claessen
- Physikalisches
Institut and Würzburg-Dresden Cluster of Excellence ct.qmat, University of Würzburg, D-97070 Würzburg, Germany
| | - Laurenz Rettig
- Fritz-Haber-Institut
der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
| |
Collapse
|
19
|
High output mode-locked laser empowered by defect regulation in 2D Bi2O2Se saturable absorber. Nat Commun 2022; 13:3855. [PMID: 35790761 PMCID: PMC9256711 DOI: 10.1038/s41467-022-31606-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Accepted: 06/16/2022] [Indexed: 12/17/2022] Open
Abstract
AbstractAtomically thin Bi2O2Se has emerged as a novel two-dimensional (2D) material with an ultrabroadband nonlinear optical response, high carrier mobility and excellent air stability, showing great potential for the realization of optical modulators. Here, we demonstrate a femtosecond solid-state laser at 1.0 µm with Bi2O2Se nanoplates as a saturable absorber (SA). Upon further defect regulation in 2D Bi2O2Se, the average power of the mode-locked laser is improved from 421 mW to 665 mW, while the pulse width is decreased from 587 fs to 266 fs. Moderate Ar+ plasma treatments are employed to precisely regulate the O and Se defect states in Bi2O2Se nanoplates. Nondegenerate pump-probe measurements show that defect engineering effectively accelerates the trapping rate and defect-assisted Auger recombination rate of photocarriers. The saturation intensity is improved from 3.6 ± 0.2 to 12.8 ± 0.6 MW cm−2 after the optimized defect regulation. The enhanced saturable absorption and ultrafast carrier lifetime endow the high-performance mode-locked laser with both large output power and short pulse duration.
Collapse
|
20
|
Wadhwa R, Ghosh A, Kumar D, Kumar P, Kumar M. Platinum nanoparticle sensitized plasmonic-enhanced broad spectral photodetection in large area vertical-aligned MoS 2flakes. NANOTECHNOLOGY 2022; 33:255702. [PMID: 35297382 DOI: 10.1088/1361-6528/ac5e85] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 03/16/2022] [Indexed: 06/14/2023]
Abstract
2D MoS2holds immense potential for electronic and optoelectronic applications due to its unique characteristics. However, the atomic-scale thickness of MoS2hinders the optical absorbance, thereby limiting its photodetection capability. Vertically-aligned MoS2(VA-MoS2) has an advantage of strong optical absorption and quick intra-layer transport, offering high speed operation. The coupling of plasmonic metal nanostructure with MoS2can further enhance the light-matter interaction. Pt/Pd (as opposed to Ag/Au) are more promising to design next-generation nano-plasmonic devices due to their intense interband activity over a broad spectral range. Herein, we report Pt nanoparticle (NPs) enhanced broadband photoresponse in VA-MoS2. The optical absorbance of MoS2is enhanced after the integration of Pt NPs, with a four-fold enhancement in photocurrent. The formation of Schottky junction at Pt-MoS2interface inhibits electron transmission, suppressing the dark current and substantially reducing NEP. The plasmonic-enabled photodetector shows enhanced responsivity (432 A W-1, 800 nm) and detectivity (1.85 × 1014Jones, 5 V) with a low response time (87 ms/84 ms), attributed to faster carrier transport. Additionally, a theoretical approach is adopted to calculate wavelength-dependent responsivity, which matches well with experimental results. These findings offer a facile approach to modulate the performance of next-generation optoelectronic devices for practical applications.
Collapse
Affiliation(s)
- Riya Wadhwa
- Functional and Renewable Energy Materials Laboratory, Department of Physics, Indian Institute of Technology Ropar, Rupnagar, Punjab-140001, India
| | - Anupam Ghosh
- Functional and Renewable Energy Materials Laboratory, Department of Physics, Indian Institute of Technology Ropar, Rupnagar, Punjab-140001, India
| | - Deepu Kumar
- Indian Institute of Technology Mandi, Himachal Pradesh-175005, India
| | - Pradeep Kumar
- Indian Institute of Technology Mandi, Himachal Pradesh-175005, India
| | - Mukesh Kumar
- Functional and Renewable Energy Materials Laboratory, Department of Physics, Indian Institute of Technology Ropar, Rupnagar, Punjab-140001, India
| |
Collapse
|
21
|
Li D, Zhang W, Suo P, Chen J, Sun K, Zou Y, Ma H, Lin X, Yan X, Zhang S, Li B, Ma G. Ultrafast Dynamics of Defect-Assisted Auger Process in PdSe 2 Films: Synergistic Interaction between Defect Trapping and Auger Effect. J Phys Chem Lett 2022; 13:2757-2764. [PMID: 35315678 DOI: 10.1021/acs.jpclett.2c00315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
By using optical pump and terahertz probe spectroscopy, we have investigated the photocarrier dynamics in PdSe2 films with different thicknesses. The experimental results reveal that the photocarrier relaxation consists of two components: a fast component of 2.5 ps that shows the layer-thickness independence and a slow component that has typical lifetime of 7.3 ps decreasing with the layer thickness. Interestingly, the relaxation times for both fast and slow components exhibited both pump fluence and temperature independence, which suggests that synergistic interactions between defect trapping and Auger effect dominate the photocarrier dynamics in PdSe2 films. A model involving a defect-assisted Auger process is proposed, which can reproduce the experimental results well. The fitting results reveal that the layer-dependent lifetime is determined by the defect density rather than carrier occupancy rate after photoexcitation. Our results underscore the interplay between the Auger process and defects in two-dimensional semiconductors.
Collapse
Affiliation(s)
- Di Li
- Department of Physics, Shanghai University, Shanghai 200444, China
| | - Wenjie Zhang
- Department of Physics, Shanghai University, Shanghai 200444, China
| | - Peng Suo
- Department of Physics, Shanghai University, Shanghai 200444, China
| | - Jiaming Chen
- Department of Physics, Shanghai University, Shanghai 200444, China
| | - Kaiwen Sun
- Department of Physics, Shanghai University, Shanghai 200444, China
| | - Yuqing Zou
- Department of Physics, Shanghai University, Shanghai 200444, China
| | - Hong Ma
- School of Physics and Electronics, Shandong Normal University, Jinan 250014, China
| | - Xian Lin
- Department of Physics, Shanghai University, Shanghai 200444, China
| | - Xiaona Yan
- Department of Physics, Shanghai University, Shanghai 200444, China
| | - Saifeng Zhang
- Department of Physics, Shanghai University, Shanghai 200444, China
| | - Bo Li
- Key Laboratory of Polar Materials and Devices (MOE), Department of Electronics, East China Normal University, Shanghai 200241, China
| | - Guohong Ma
- Department of Physics, Shanghai University, Shanghai 200444, China
| |
Collapse
|
22
|
Khatua DP, Singh A, Gurung S, Khan S, Tanwar M, Kumar R, Jayabalan J. Ultrafast carrier dynamics in a monolayer MoS 2at carrier densities well above Mott density. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:155401. [PMID: 35062012 DOI: 10.1088/1361-648x/ac4dbf] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Accepted: 01/21/2022] [Indexed: 06/14/2023]
Abstract
Due to the growing interest in monolayer (ML) molybdenum disulfide (MoS2) in several optoelectronic applications like lasers, detectors, sensors, it is important to understand the ultrafast behavior of the excited carriers in this material. In this article, a comprehensive study of the charge carrier dynamics of a monolayer MoS2flake has been studied using transient transmission technique near A-exciton under high excitation densities well above the Mott density. Fluence dependent studies has been carried out to understand the origin of the processes which modifies its optical response under excitation. The dissociation of excitons leads to an observed fast bandgap renormalization. At later times when large number of carriers relax the remaining carriers forms excitons leading to a bleaching effect.
Collapse
Affiliation(s)
- Durga Prasad Khatua
- Nano Science Laboratory, Materials Science Section, Raja Ramanna Centre for Advanced Technology, Indore, 452013 India
- Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai, 400094, India
| | - Asha Singh
- Nano Science Laboratory, Materials Science Section, Raja Ramanna Centre for Advanced Technology, Indore, 452013 India
| | - Sabina Gurung
- Nano Science Laboratory, Materials Science Section, Raja Ramanna Centre for Advanced Technology, Indore, 452013 India
- Department of Physics, Institute for Quantum Electronics, ETH Zurich, 8093, Switzerland
| | - Salahuddin Khan
- Nano Science Laboratory, Materials Science Section, Raja Ramanna Centre for Advanced Technology, Indore, 452013 India
| | - Manushree Tanwar
- Materials and Device Laboratory, Department of Physics, Indian Institute of Technology Indore, Simrol, 453552, India
| | - Rajesh Kumar
- Materials and Device Laboratory, Department of Physics, Indian Institute of Technology Indore, Simrol, 453552, India
| | - J Jayabalan
- Nano Science Laboratory, Materials Science Section, Raja Ramanna Centre for Advanced Technology, Indore, 452013 India
- Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai, 400094, India
| |
Collapse
|
23
|
Yao J, Chen C, Zhang J, Zhang L, Zhang W, Shen JW, Liang L. Molecular understanding of charge effect on desalination performance in lamellar MoS 2 membranes. Phys Chem Chem Phys 2022; 24:26879-26889. [DOI: 10.1039/d2cp02145e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The effect of atomic charge information on the desalination performance of lamellar MoS2 membranes was investigated at the molecular level.
Collapse
Affiliation(s)
- Junhui Yao
- Department of Chemistry, Key Laboratory of Surface & Interface Science of Polymer Materials of Zhejiang Province. Zhejiang Sci-Tech University, Hangzhou, 310018, P. R. China
| | - Chen Chen
- Department of Chemistry, Key Laboratory of Surface & Interface Science of Polymer Materials of Zhejiang Province. Zhejiang Sci-Tech University, Hangzhou, 310018, P. R. China
| | - Jing Zhang
- Department of Chemistry, Key Laboratory of Surface & Interface Science of Polymer Materials of Zhejiang Province. Zhejiang Sci-Tech University, Hangzhou, 310018, P. R. China
| | - Li Zhang
- Department of Chemistry, Key Laboratory of Surface & Interface Science of Polymer Materials of Zhejiang Province. Zhejiang Sci-Tech University, Hangzhou, 310018, P. R. China
| | - Wei Zhang
- Department of Chemistry, Key Laboratory of Surface & Interface Science of Polymer Materials of Zhejiang Province. Zhejiang Sci-Tech University, Hangzhou, 310018, P. R. China
| | - Jia-Wei Shen
- School of Pharmacy, Hangzhou Normal University, Hangzhou, 310016, P. R. China
| | - Lijun Liang
- College of Life Information Science and Instrument Engineering, Hangzhou Dianzi University, Hangzhou, 310018, P. R. China
| |
Collapse
|
24
|
Picosecond electrical response in graphene/MoTe2 heterojunction with high responsivity in the near infrared region. FUNDAMENTAL RESEARCH 2021. [DOI: 10.1016/j.fmre.2021.09.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
|
25
|
Dandu M, Gupta G, Majumdar K. Negative Differential Photoconductance as a Signature of Nonradiative Energy Transfer in van der Waals Heterojunction. ACS NANO 2021; 15:16432-16441. [PMID: 34644047 DOI: 10.1021/acsnano.1c05844] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The physical proximity of layered materials in their van der Waals heterostructures (vdWhs) aids interfacial phenomena such as charge transfer (CT) and energy transfer (ET). Besides providing fundamental insights, CT and ET also offer routes to engineer optoelectronic properties of vdWhs. For example, harnessing ET in vdWhs can help to overcome the limitations of optical absorption imposed by the ultra-thin nature of layered materials and thus provide an opportunity for in situ enhancement of quantum efficiency for light-harvesting and sensing applications. While several spectroscopic studies on vdWhs probed the dynamics of CT and ET, the possible contribution of ET in the photocurrent generation remains largely unexplored. In this work, we investigate the role of nonradiative energy transfer (NRET) in the photocurrent through a vertical vdWh of SnSe2/MoS2/TaSe2. We observe an unusual negative differential photoconductance (NDPC) arising from the existence of NRET across the SnSe2/MoS2 junction. Modulation of the NRET-driven NDPC characteristics with optical power results in a striking transition of the photocurrent's power law from a sublinear to a superlinear regime. Our observations reveal the nontrivial influence of ET on the photoresponse of vdWhs, which offer insights to harness ET in synergy with CT for vdWh based next-generation optoelectronics.
Collapse
Affiliation(s)
- Medha Dandu
- Department of Electrical Communication Engineering, Indian Institute of Science, Bangalore 560012, India
| | - Garima Gupta
- Department of Electrical Communication Engineering, Indian Institute of Science, Bangalore 560012, India
| | - Kausik Majumdar
- Department of Electrical Communication Engineering, Indian Institute of Science, Bangalore 560012, India
| |
Collapse
|
26
|
Sulas-Kern DB, Zhang H, Li Z, Blackburn JL. Interplay between microstructure, defect states, and mobile charge generation in transition metal dichalcogenide heterojunctions. NANOSCALE 2021; 13:8188-8198. [PMID: 33884391 DOI: 10.1039/d1nr00384d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Two-dimensional transition metal dichalcogenides (2D-TMDCs) have gained attention for their promise in next-generation energy-harvesting and quantum computing technologies, but realizing these technologies requires a greater understanding of TMDC properties that influence their photophysics. To this end, we discuss here the interplay between TMDC microstructure and defects with the charge generation yield, lifetime, and mobility. As a model system, we compare monolayer-only and monolayer-rich MoS2 grown by chemical vapor deposition, and we employ the TMDCs in Type-II charge-separating heterojunctions with semiconducting single-walled carbon nanotubes (s-SWCNTs). Our results suggest longer lifetimes and higher yields of mobile carriers in samples containing a small fraction of defect-rich multilayer islands on predominately monolayer MoS2. Compared to the monolayer-only heterojunctions, the carrier lifetimes increase from 0.73 μs to 4.71 μs, the hole transfer yield increases from 23% to 34%, and the electron transfer yield increases from 39% to 59%. We reach these conclusions using a unique combination of microwave photoconductivity (which probes only mobile carriers) along with transient absorption spectroscopy (which identifies spectral signatures unique to each material and type of photoexcited quasiparticle, but does not probe mobility). Our results highlight the substantial changes in photophysics that can occur from small changes in TMDC microstructure and defect density, where the presence of defects does not necessarily preclude improvements in charge generation.
Collapse
Affiliation(s)
- Dana B Sulas-Kern
- National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, USA.
| | | | | | | |
Collapse
|
27
|
Gao L, Hu Z, Lu J, Liu H, Ni Z. Defect-related dynamics of photoexcited carriers in 2D transition metal dichalcogenides. Phys Chem Chem Phys 2021; 23:8222-8235. [PMID: 33875990 DOI: 10.1039/d1cp00006c] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two-dimensional (2D) transition metal dichalcogenides (TMDs) exhibit enormous potential in the field of optoelectronics. The high performance of TMD materials and optoelectronic devices significantly depends on processes involved in photoelectric conversion, including photo-excitation, relaxation, transportation, and recombination. Remarkably, inevitable defects in materials prolong or shorten the characteristic time of these processes and even bring about new photoelectric conversion channels, namely, the defect-related relaxation pathways of photoexcited carriers tailor the performance of photoelectric applications. In recent years, there have been numerous investigations in exploring the variant transient signals caused by defects in TMDs utilizing ultrafast spectroscopies. They have the capability in providing an accurate and overall representation of ultrafast processes owing to the subtle temporal resolution. The defect-related mechanisms occurring in different time scales (from femtosecond (fs) to microsecond (μs)) play influential roles throughout the relaxation process of photoexcited species. Herein, we review the defect-related relaxation mechanisms of photoexcited species in TMDs according to the time scale utilizing ultrafast spectroscopy techniques. By interpreting and summarizing the defect-related transient signals, we furnish the direction in material design and performance optimization.
Collapse
Affiliation(s)
- Lei Gao
- School of Physics and Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing 211189, China.
| | - Zhenliang Hu
- School of Physics and Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing 211189, China.
| | - Junpeng Lu
- School of Physics and Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing 211189, China.
| | - Hongwei Liu
- Jiangsu Key Lab on Opto-Electronic Technology, School of Physics and Technology, Nanjing Normal University, Nanjing 210023, China
| | - Zhenhua Ni
- School of Physics and Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing 211189, China.
| |
Collapse
|
28
|
Fu S, du Fossé I, Jia X, Xu J, Yu X, Zhang H, Zheng W, Krasel S, Chen Z, Wang ZM, Tielrooij KJ, Bonn M, Houtepen AJ, Wang HI. Long-lived charge separation following pump-wavelength-dependent ultrafast charge transfer in graphene/WS 2 heterostructures. SCIENCE ADVANCES 2021; 7:7/9/eabd9061. [PMID: 33637529 PMCID: PMC7909886 DOI: 10.1126/sciadv.abd9061] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Accepted: 01/12/2021] [Indexed: 05/27/2023]
Abstract
Van der Waals heterostructures consisting of graphene and transition metal dichalcogenides have shown great promise for optoelectronic applications. However, an in-depth understanding of the critical processes for device operation, namely, interfacial charge transfer (CT) and recombination, has so far remained elusive. Here, we investigate these processes in graphene-WS2 heterostructures by complementarily probing the ultrafast terahertz photoconductivity in graphene and the transient absorption dynamics in WS2 following photoexcitation. We observe that separated charges in the heterostructure following CT live extremely long: beyond 1 ns, in contrast to ~1 ps charge separation reported in previous studies. This leads to efficient photogating of graphene. Furthermore, for the CT process across graphene-WS2 interfaces, we find that it occurs via photo-thermionic emission for sub-A-exciton excitations and direct hole transfer from WS2 to the valence band of graphene for above-A-exciton excitations. These findings provide insights to further optimize the performance of optoelectronic devices, in particular photodetection.
Collapse
Affiliation(s)
- Shuai Fu
- Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
| | - Indy du Fossé
- Optoelectronic Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, Netherlands
| | - Xiaoyu Jia
- Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
| | - Jingyin Xu
- Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, P. R. China
| | - Xiaoqing Yu
- Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
| | - Heng Zhang
- Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
| | - Wenhao Zheng
- Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
| | - Sven Krasel
- Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
| | - Zongping Chen
- School of Materials Science and Engineering, Zhejiang University, Zheda Road 38, Hangzhou 310027, China
| | - Zhiming M Wang
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, P. R. China
| | - Klaas-Jan Tielrooij
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), BIST and CSIC, Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - Mischa Bonn
- Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
| | - Arjan J Houtepen
- Optoelectronic Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, Netherlands
| | - Hai I Wang
- Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany.
| |
Collapse
|
29
|
Wang Y, Nie Z, Wang F. Modulation of photocarrier relaxation dynamics in two-dimensional semiconductors. LIGHT, SCIENCE & APPLICATIONS 2020; 9:192. [PMID: 33298847 PMCID: PMC7680791 DOI: 10.1038/s41377-020-00430-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/12/2020] [Revised: 10/09/2020] [Accepted: 11/06/2020] [Indexed: 06/12/2023]
Abstract
Due to strong Coulomb interactions, two-dimensional (2D) semiconductors can support excitons with large binding energies and complex many-particle states. Their strong light-matter coupling and emerging excitonic phenomena make them potential candidates for next-generation optoelectronic and valleytronic devices. The relaxation dynamics of optically excited states are a key ingredient of excitonic physics and directly impact the quantum efficiency and operating bandwidth of most photonic devices. Here, we summarize recent efforts in probing and modulating the photocarrier relaxation dynamics in 2D semiconductors. We classify these results according to the relaxation pathways or mechanisms they are associated with. The approaches discussed include both tailoring sample properties, such as the defect distribution and band structure, and applying external stimuli such as electric fields and mechanical strain. Particular emphasis is placed on discussing how the unique features of 2D semiconductors, including enhanced Coulomb interactions, sensitivity to the surrounding environment, flexible van der Waals (vdW) heterostructure construction, and non-degenerate valley/spin index of 2D transition metal dichalcogenides (TMDs), manifest themselves during photocarrier relaxation and how they can be manipulated. The extensive physical mechanisms that can be used to modulate photocarrier relaxation dynamics are instrumental for understanding and utilizing excitonic states in 2D semiconductors.
Collapse
Affiliation(s)
- Yuhan Wang
- School of Electronic Science and Engineering and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
- Key Laboratory of Intelligent Optical Sensing and Manipulation, Ministry of Education, Nanjing University, Nanjing, 210093, China
| | - Zhonghui Nie
- MIIT Key Laboratory of Advanced Display Materials and Devices, Institute of Optoelectronics & Nanomaterials, College of Materials Science and Engineering, Nanjing University of Science and Technology, 210094, Nanjing, China
| | - Fengqiu Wang
- School of Electronic Science and Engineering and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China.
- Key Laboratory of Intelligent Optical Sensing and Manipulation, Ministry of Education, Nanjing University, Nanjing, 210093, China.
| |
Collapse
|
30
|
Chi Z, Chen HH, Chen Z, Chen HL. Unveiling defect-mediated carrier dynamics in few-layer MoS2 prepared by ion exchange method via ultrafast Vis-NIR-MIR spectroscopy. CHINESE J CHEM PHYS 2020. [DOI: 10.1063/1674-0068/cjcp2007123] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Affiliation(s)
- Zhen Chi
- The Laboratory of Soft Matter Physics, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Institute of Photo-biophysics, School of Physics and Electronics, Henan University, Kaifeng 475004, China
| | - Hui-hui Chen
- Department of Materials Physics and Chemistry, Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, School of Materials Science and Engineering, Beijing Institute of Technology Institution, Beijing 100081, China
| | - Zhuo Chen
- Department of Materials Physics and Chemistry, Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, School of Materials Science and Engineering, Beijing Institute of Technology Institution, Beijing 100081, China
| | - Hai-long Chen
- The Laboratory of Soft Matter Physics, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan 523808, China
| |
Collapse
|
31
|
Zimmermann JE, Li B, Hone JC, Höfer U, Mette G. Second-harmonic imaging microscopy for time-resolved investigations of transition metal dichalcogenides. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:485901. [PMID: 32716316 DOI: 10.1088/1361-648x/aba946] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 07/23/2020] [Indexed: 06/11/2023]
Abstract
Two-dimensional transition metal dichalcogenides (TMD) have shown promise for various applications in optoelectronics and so-called valleytronics. Their operation and performance strongly depend on the stacking of individual layers. Here, optical second-harmonic generation in imaging mode is shown to be a versatile tool for systematic time-resolved investigations of TMD monolayers and heterostructures in consideration of the material's structure. Large sample areas can be probed without the need of any mapping or scanning. By means of polarization dependent measurements, the crystalline orientation of monolayers or the stacking angles of heterostructures can be evaluated for the whole field of view. Pump-probe experiments then allow to correlate observed transient changes of the second-harmonic response with the underlying structure. The corresponding time-resolution is virtually limited by the pulse duration of the used laser. As an example, polarization dependent and time-resolved measurements on mono- and multilayer MoS2flakes grown on a SiO2/ Si(001) substrate are presented.
Collapse
Affiliation(s)
- J E Zimmermann
- Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, 35032 Marburg, Germany
| | - B Li
- Department of Mechanical Engineering, Columbia University, New York 10027, United States of America
| | - J C Hone
- Department of Mechanical Engineering, Columbia University, New York 10027, United States of America
| | - U Höfer
- Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, 35032 Marburg, Germany
| | - G Mette
- Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, 35032 Marburg, Germany
| |
Collapse
|
32
|
Tsai HS, Huang YH, Tsai PC, Chen YJ, Ahn H, Lin SY, Lu YJ. Ultrafast Exciton Dynamics in Scalable Monolayer MoS 2 Synthesized by Metal Sulfurization. ACS OMEGA 2020; 5:10725-10730. [PMID: 32455191 PMCID: PMC7240830 DOI: 10.1021/acsomega.0c00187] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 04/07/2020] [Indexed: 05/08/2023]
Abstract
Excitons in monolayer transition metal dichalcogenides (TMDs) have exceptionally large binding energies and dominate the optical properties of materials. Exploring the relaxation behavior of excitons is crucial for understanding the fundamental physics as well as the performance of TMD-based optoelectronic devices. However, ultrafast carrier dynamics is sensitive to the structural defects and surface conditions of TMDs, depending on the growth or transfer process. Here, we utilized pump-probe transient absorption (TA) spectroscopy with a white-light probe to investigate the dynamics of excitons in monolayer MoS2 synthesized by the metal sulfurization method. The sulfurization method was used for the fabrication of large-scale, continuous, and uniform thin films with a controllable number of layers. The excitation dynamics of the wafer-size monolayer MoS2 is found to be comparable to that of monolayer MoS2 flakes grown by chemical vapor deposition (CVD). The dominant processes of carrier relaxation in the monolayer MoS2 are exciton-exciton annihilation (hundreds of femtoseconds), the trapping of the excitons by surface states (a few picoseconds), and interband carrier-phonon scattering (tens of picoseconds). Moreover, the induced absorption due to mid-gap defects, which is often observed for samples fabricated by growth methods, such as CVD, is not observed for our continuous and uniform monolayer films. Understanding the charge carrier dynamics of the exciton in the scalable and uniform monolayer MoS2 can provide physical insights that are valuable in the design and development of complex 2D devices.
Collapse
Affiliation(s)
- Hsu-Sheng Tsai
- Research
Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan
- Space
Environment Simulation Research Infrastructure, Harbin Institute of Technology, 150001, Harbin, China
| | - Yung-Hung Huang
- Research
Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan
- Department
of Materials Science and Engineering, National
Dong Hwa University, Hualien 97401, Taiwan
| | - Po-Cheng Tsai
- Research
Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan
| | - Yi-Jia Chen
- Department
of Materials Science and Engineering, National
Dong Hwa University, Hualien 97401, Taiwan
| | - Hyeyoung Ahn
- Department
of Photonics, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu 30013, Taiwan
| | - Shih-Yen Lin
- Research
Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan
- Graduate
Institute of Electronics Engineering, National
Taiwan University, Taipei 10617, Taiwan
| | - Yu-Jung Lu
- Research
Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan
- Department
of Physics, National Taiwan University, Taipei 10617, Taiwan
| |
Collapse
|
33
|
Liu H, Wang C, Zuo Z, Liu D, Luo J. Direct Visualization of Exciton Transport in Defective Few-Layer WS 2 by Ultrafast Microscopy. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e1906540. [PMID: 31773833 DOI: 10.1002/adma.201906540] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2019] [Revised: 11/03/2019] [Indexed: 06/10/2023]
Abstract
As defects usually limit the exciton diffusion in 2D transition metal dichalcogenides (TMDCs), the interaction knowledge of defects and exciton transport is crucial for achieving efficient TMDC-based devices. A direct visualization of defect-modulated exciton transport is developed in few-layer WS2 by ultrafast transient absorption microscopy. Atomic-scale defects are introduced by argon plasma treatment and identified by aberration-corrected scanning transmission electron microscopy. Neutral excitons can be captured by defects to form bound excitons in 7.75-17.88 ps, which provide a nonradiative relaxation channel, leading to decreased exciton lifetime and diffusion coefficient. The exciton diffusion length of defective sample has a drastic reduction from 349.44 to 107.40 nm. These spatially and temporally resolved measurements reveal the interaction mechanism between defects and exciton transport dynamics in 2D TMDCs, giving a guideline for designing high-performance TMDC-based devices.
Collapse
Affiliation(s)
- Huan Liu
- State Key Laboratory of Tribology, Tsinghua University, Beijing, 100084, P. R. China
| | - Chong Wang
- State Key Laboratory of Tribology, Tsinghua University, Beijing, 100084, P. R. China
| | - Zhengguang Zuo
- State Key Laboratory of Tribology, Tsinghua University, Beijing, 100084, P. R. China
| | - Dameng Liu
- State Key Laboratory of Tribology, Tsinghua University, Beijing, 100084, P. R. China
| | - Jianbin Luo
- State Key Laboratory of Tribology, Tsinghua University, Beijing, 100084, P. R. China
| |
Collapse
|
34
|
Song Q, Chai L, Liu W, Ma Q, Li Y, Hu M. THz polarization-sensitive characterization of a large-area multilayer rhenium diselenide nanofilm. NANOTECHNOLOGY 2019; 30:505203. [PMID: 31509805 DOI: 10.1088/1361-6528/ab4377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Recently, rhenium diselenide (ReSe2) has attracted considerable attention due to its high anisotropy in the layer plane, which makes it a promising candidate for wide applications in electronics and optoelectronics. In this paper, we focus on the polarization-sensitive characteristics of a large-area multilayer ReSe2 nanofilm in the terahertz (THz) region under passive and active conditions by means of THz time-domain spectroscopy. We demonstrate the passive ReSe2 nanofilm with intrinsic THz polarization anisotropy. Maximum transmittance occurs only when the polarization direction of the incident THz wave is along the Re-chains direction. More importantly, THz polarization properties of the active ReSe2 nanofilm by an external electric field applied in a selected directions are also demonstrated. The modulation depth of the THz transmission is up to 16% and the response time is on the order of picoseconds. In addition, a comparative experiment is performed on three kinds of THz polarizers, i.e., ReSe2 nanofilm, carbon nanotubes (CNTs) and wire-gird, respectively. The results prove that the performance of the polarizer based on the active ReSe2 nanofilm is comparable with those of CNTs and the THz wire-gird polarizer. Based on these studies, we believe that the polarization-sensitive ReSe2 nanofilm can find important applications in ultrafast switches, filters and modulation devices in the THz region.
Collapse
Affiliation(s)
- Qi Song
- School of Precision Instrument and Opto-electronics engineering, Key Laboratory of Opto-electronic Information Technology (Ministry of Education), Ultrafast Laser Laboratory, Tianjin University, Tianjin, People's Republic of China
| | | | | | | | | | | |
Collapse
|
35
|
Yu K, Wang J, Chen J, Wang GP. Inhomogeneous photocarrier dynamics and transport in monolayer MoS 2 by ultrafast microscopy. NANOTECHNOLOGY 2019; 30:485701. [PMID: 31437820 DOI: 10.1088/1361-6528/ab3dc2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Monolayer MoS2 as a member of two-dimensional transition metal dichalcogenides (TMDs) has attracted considerable attention due to its superior optoelectronic properties. Understanding the photocarrier dynamics and transport in these two dimensional systems is beneficial for applications from photovoltaics to sensing. However, various structural defects strongly impact the dynamics and transport of photocarriers. Especially there lacks a precise measuring and understanding of photocarrier transport in TMDs. Here, femtosecond transient absorption spectroscopy and microscopy were employed to study the photocarrier dynamics and transport in monolayer MoS2. Defect correlated photocarrier dynamics are observed across the monolayer MoS2 where exciton formation and nonradiative recombination are the two dominant decay processes. To the best of our knowledge, we report two distinct photocarrier transport regimes in MoS2 for the first time with diffusion coefficients of [Formula: see text] cm2 s-1 and [Formula: see text] cm2 s-1, by taking advantages of ultrafast microscopy with ∼20 nm spatial precision and ∼200 fs temporal resolution. These two regimes are ascribed to fast hot photocarrier diffusion and slow phonon-limited thermal diffusion, respectively. The results indicate that the initial fast photocarrier transport is less dependent on structural defects compared to photocarrier relaxation dynamics which may be useful for hot photocarrier extraction applications.
Collapse
Affiliation(s)
- Kuai Yu
- Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, People's Republic of China
| | | | | | | |
Collapse
|
36
|
Huang J, Dong N, McEvoy N, Wang L, Coileáin CÓ, Wang H, Cullen CP, Chen C, Zhang S, Zhang L, Wang J. Surface-State Assisted Carrier Recombination and Optical Nonlinearities in Bulk to 2D Nonlayered PtS. ACS NANO 2019; 13:13390-13402. [PMID: 31661247 DOI: 10.1021/acsnano.9b06782] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Cooperite, or platinum sulfide (PtS), is a rare mineral that generally exists as microscale, irregularly shaped crystallites. The presence of impurities, in both naturally occurring and synthesized samples, has hindered the study of its optical properties in the past. In this work, we prepare large-scale, uniform PtS films in bulk to two-dimensional form through the thermally assisted conversion method. An abnormal trend is observed in linear spectral studies whereby the optical bandgap narrows as the film thickness decreases. A model based on the continuous distribution of carriers in real space, which can be regarded as a quantum well normal to the plane, is used to describe the thickness-dependent carrier recombination phenomenon. In the nonlinear optical measurements, PtS exhibits ultrafast saturable absorption and self-defocusing properties in the visible region, which are dominated by the resonant electronic nonlinearities.
Collapse
Affiliation(s)
- Jiawei Huang
- Laboratory of Micro-Nano Optoelectronic Materials and Devices, Key Laboratory of Materials for High-Power Laser , Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences , Shanghai 201800 , China
- Center of Materials Science and Optoelectronics Engineering , University of Chinese Academy of Sciences , Beijing 100049 , China
- CAS Center for Excellence in Ultra-intense Laser Science , Shanghai 201800 , China
| | - Ningning Dong
- Laboratory of Micro-Nano Optoelectronic Materials and Devices, Key Laboratory of Materials for High-Power Laser , Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences , Shanghai 201800 , China
- Center of Materials Science and Optoelectronics Engineering , University of Chinese Academy of Sciences , Beijing 100049 , China
- CAS Center for Excellence in Ultra-intense Laser Science , Shanghai 201800 , China
| | - Niall McEvoy
- Advanced Materials and BioEngineering Research (AMBER) Centre and School of Chemistry , Trinity College Dublin , Dublin 2 , Ireland
| | - Lei Wang
- Laboratory of Micro-Nano Optoelectronic Materials and Devices, Key Laboratory of Materials for High-Power Laser , Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences , Shanghai 201800 , China
- Center of Materials Science and Optoelectronics Engineering , University of Chinese Academy of Sciences , Beijing 100049 , China
- CAS Center for Excellence in Ultra-intense Laser Science , Shanghai 201800 , China
| | - Cormac Ó Coileáin
- Advanced Materials and BioEngineering Research (AMBER) Centre and School of Chemistry , Trinity College Dublin , Dublin 2 , Ireland
| | - Hongqiang Wang
- Laboratory of Micro-Nano Optoelectronic Materials and Devices, Key Laboratory of Materials for High-Power Laser , Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences , Shanghai 201800 , China
- Center of Materials Science and Optoelectronics Engineering , University of Chinese Academy of Sciences , Beijing 100049 , China
- CAS Center for Excellence in Ultra-intense Laser Science , Shanghai 201800 , China
| | - Conor P Cullen
- Advanced Materials and BioEngineering Research (AMBER) Centre and School of Chemistry , Trinity College Dublin , Dublin 2 , Ireland
| | - Chenduan Chen
- Laboratory of Micro-Nano Optoelectronic Materials and Devices, Key Laboratory of Materials for High-Power Laser , Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences , Shanghai 201800 , China
- Center of Materials Science and Optoelectronics Engineering , University of Chinese Academy of Sciences , Beijing 100049 , China
- CAS Center for Excellence in Ultra-intense Laser Science , Shanghai 201800 , China
| | - Saifeng Zhang
- Laboratory of Micro-Nano Optoelectronic Materials and Devices, Key Laboratory of Materials for High-Power Laser , Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences , Shanghai 201800 , China
- Center of Materials Science and Optoelectronics Engineering , University of Chinese Academy of Sciences , Beijing 100049 , China
- CAS Center for Excellence in Ultra-intense Laser Science , Shanghai 201800 , China
| | - Long Zhang
- Laboratory of Micro-Nano Optoelectronic Materials and Devices, Key Laboratory of Materials for High-Power Laser , Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences , Shanghai 201800 , China
- Center of Materials Science and Optoelectronics Engineering , University of Chinese Academy of Sciences , Beijing 100049 , China
- CAS Center for Excellence in Ultra-intense Laser Science , Shanghai 201800 , China
| | - Jun Wang
- Laboratory of Micro-Nano Optoelectronic Materials and Devices, Key Laboratory of Materials for High-Power Laser , Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences , Shanghai 201800 , China
- Center of Materials Science and Optoelectronics Engineering , University of Chinese Academy of Sciences , Beijing 100049 , China
- CAS Center for Excellence in Ultra-intense Laser Science , Shanghai 201800 , China
- State Key Laboratory of High Field Laser Physics , Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences , Shanghai 201800 , China
| |
Collapse
|
37
|
Song B, Gu H, Fang M, Ho YT, Chen X, Jiang H, Liu S. Complex Optical Conductivity of Two-Dimensional MoS 2: A Striking Layer Dependency. J Phys Chem Lett 2019; 10:6246-6252. [PMID: 31490075 DOI: 10.1021/acs.jpclett.9b02111] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The complex optical conductivities of two-dimensaionl (2D) materials are fundamental for extended applications of related optoelectronic devices. Here, we systematically investigate the layer-dependent evolutions in the complex optical conductivities of 1-6 layer 2D MoS2 over an ultrawide spectral range (0.73-6.42 eV) by spectroscopic ellipsometry. We identify five feature peaks (A-E) in the optical conductivity spectra, which present interesting layer dependencies due to the scaling effect. Results suggest that the center energies of peaks A and B are nearly layer-independent, while those of peaks C and D exhibit redshifts as the layer increases. We interpret these layer-dependent evolutions as the competition between the decreasing exciton effect and the prominent band shrinkage with the increasing layer number. Additionally, the applicability of the classical slab model and the surface current model in evaluating the optical conductivities of 2D MoS2 with different layers is discussed from an experimental perspective.
Collapse
Affiliation(s)
- Baokun Song
- State Key Laboratory of Digital Manufacturing Equipment and Technology , Huazhong University of Science and Technology , Wuhan 430074 , Hubei , China
| | - Honggang Gu
- State Key Laboratory of Digital Manufacturing Equipment and Technology , Huazhong University of Science and Technology , Wuhan 430074 , Hubei , China
| | - Mingsheng Fang
- State Key Laboratory of Digital Manufacturing Equipment and Technology , Huazhong University of Science and Technology , Wuhan 430074 , Hubei , China
| | - Yen-Teng Ho
- Department of Materials Science and Engineering , National Chiao Tung University , Hsinchu 30010 , Taiwan , China
| | - Xiuguo Chen
- State Key Laboratory of Digital Manufacturing Equipment and Technology , Huazhong University of Science and Technology , Wuhan 430074 , Hubei , China
| | - Hao Jiang
- State Key Laboratory of Digital Manufacturing Equipment and Technology , Huazhong University of Science and Technology , Wuhan 430074 , Hubei , China
| | - Shiyuan Liu
- State Key Laboratory of Digital Manufacturing Equipment and Technology , Huazhong University of Science and Technology , Wuhan 430074 , Hubei , China
| |
Collapse
|
38
|
Li L, Lin MF, Zhang X, Britz A, Krishnamoorthy A, Ma R, Kalia RK, Nakano A, Vashishta P, Ajayan P, Hoffmann MC, Fritz DM, Bergmann U, Prezhdo OV. Phonon-Suppressed Auger Scattering of Charge Carriers in Defective Two-Dimensional Transition Metal Dichalcogenides. NANO LETTERS 2019; 19:6078-6086. [PMID: 31434484 DOI: 10.1021/acs.nanolett.9b02005] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Two-dimensional transition metal dichalcogenides (TMDs) draw strong interest in materials science, with applications in optoelectronics and many other fields. Good performance requires high carrier concentrations and long lifetimes. However, high concentrations accelerate energy exchange between charged particles by Auger-type processes, especially in TMDs where many-body interactions are strong, thus facilitating carrier trapping. We report time-resolved optical pump-THz probe measurements of carrier lifetimes as a function of carrier density. Surprisingly, the lifetime reduction with increased density is very weak. It decreases only by 20% when we increase the pump fluence 100 times. This unexpected feature of the Auger process is rationalized by our time-domain ab initio simulations. The simulations show that phonon-driven trapping competes successfully with the Auger process. On the one hand, trap states are relatively close to band edges, and phonons accommodate efficiently the electronic energy during the trapping. On the other hand, trap states localize around defects, and the overlap of trapped and free carriers is small, decreasing carrier-carrier interactions. At low carrier densities, phonons provide the main charge trapping mechanism, decreasing carrier lifetimes compared to defect-free samples. At high carrier densities, phonons suppress Auger processes and lower the dependence of the trapping rate on carrier density. Our results provide theoretical insights into the diverse roles played by phonons and Auger processes in TMDs and generate guidelines for defect engineering to improve device performance at high carrier densities.
Collapse
Affiliation(s)
- Linqiu Li
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
| | - Ming-Fu Lin
- Linac Coherent Light Source , SLAC National Accelerator Laboratory , Menlo Park , California 94025 , United States
| | - Xiang Zhang
- Department of Materials Science and Nanoengineering , Rice University , Houston , Texas 77005 , United States
| | - Alexander Britz
- Linac Coherent Light Source , SLAC National Accelerator Laboratory , Menlo Park , California 94025 , United States
- Stanford PULSE Institute , SLAC National Accelerator Laboratory , Menlo Park , California 94025 , United States
| | - Aravind Krishnamoorthy
- Collaboratory for Advanced Computing and Simulations, Department of Physics &Astronomy, Department of Computer Science, Department of Chemical Engineering & Materials Science, Department of Biological Sciences , University of Southern California , Los Angeles , California 90089 , United States
| | - Ruru Ma
- Collaboratory for Advanced Computing and Simulations, Department of Physics &Astronomy, Department of Computer Science, Department of Chemical Engineering & Materials Science, Department of Biological Sciences , University of Southern California , Los Angeles , California 90089 , United States
| | - Rajiv K Kalia
- Collaboratory for Advanced Computing and Simulations, Department of Physics &Astronomy, Department of Computer Science, Department of Chemical Engineering & Materials Science, Department of Biological Sciences , University of Southern California , Los Angeles , California 90089 , United States
| | - Aiichiro Nakano
- Collaboratory for Advanced Computing and Simulations, Department of Physics &Astronomy, Department of Computer Science, Department of Chemical Engineering & Materials Science, Department of Biological Sciences , University of Southern California , Los Angeles , California 90089 , United States
| | - Priya Vashishta
- Collaboratory for Advanced Computing and Simulations, Department of Physics &Astronomy, Department of Computer Science, Department of Chemical Engineering & Materials Science, Department of Biological Sciences , University of Southern California , Los Angeles , California 90089 , United States
| | - Pulickel Ajayan
- Department of Materials Science and Nanoengineering , Rice University , Houston , Texas 77005 , United States
| | - Matthias C Hoffmann
- Linac Coherent Light Source , SLAC National Accelerator Laboratory , Menlo Park , California 94025 , United States
| | - David M Fritz
- Linac Coherent Light Source , SLAC National Accelerator Laboratory , Menlo Park , California 94025 , United States
| | - Uwe Bergmann
- Stanford PULSE Institute , SLAC National Accelerator Laboratory , Menlo Park , California 94025 , United States
| | - Oleg V Prezhdo
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
- Department of Physics & Astronomy , University of Southern California , Los Angeles , California 90089 , United States
| |
Collapse
|
39
|
Wang M, Yin H, Zhou Y, Sui C, Wang Y, Meng X, Waterhouse GIN, Ai S. Photoelectrochemical biosensor for microRNA detection based on a MoS 2/g-C 3N 4/black TiO 2 heterojunction with Histostar@AuNPs for signal amplification. Biosens Bioelectron 2019; 128:137-143. [PMID: 30660928 DOI: 10.1016/j.bios.2018.12.048] [Citation(s) in RCA: 88] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 12/12/2018] [Accepted: 12/21/2018] [Indexed: 12/14/2022]
Abstract
Herein, a novel photoelectrochemical (PEC) biosensor was developed for the ultrasensitive detection of microRNA-396a based on a MoS2/g-C3N4/black TiO2 heterojunction as the photoactive material and gold nanoparticles carrying Histostar antibodies (Histostar@AuNPs) for signal amplification. Briefly, MoS2/g-C3N4/black TiO2 was deposited on an indium tin oxide (ITO) electrode surface, after which gold nanoparticles (AuNPs) and probe DNA were assembled on the modified electrode. Hybridization with miRNA-396a resulted in a rigid DNA: RNA hybrid being formed, which was recognized by the S9.6 antibody. The captured antibody can further conjugate with the secondary IgG antibodies of Histostar@AuNPs, thereby leading to the immobilization of horse radish peroxidase (HRP). In the presence of HRP, the oxidation of 4-chloro-1-naphthol (4-CN) by H2O2 was accelerated, producing the insoluble product benzo-4-chlorohexadienone on the electrode surface and causing a significant decrease in the photocurrent. The developed biosensor could detect miRNA-396a at concentrations from 0.5 fM to 5000 fM, with a detection limit of 0.13 fM. Further, the proposed method can also be used to investigate the effect of heavy metal ions on the expression level of miRNAs. Results suggest that the biosensor developed herein offers a promising platform for the ultrasensitive detection of miRNA.
Collapse
Affiliation(s)
- Minghui Wang
- College of Chemistry and Material Science, Shandong Agricultural University, Taian 271018, PR China
| | - Huanshun Yin
- College of Chemistry and Material Science, Shandong Agricultural University, Taian 271018, PR China.
| | - Yunlei Zhou
- College of Chemistry and Material Science, Shandong Agricultural University, Taian 271018, PR China
| | - Chengji Sui
- College of Chemistry and Material Science, Shandong Agricultural University, Taian 271018, PR China
| | - Yue Wang
- College of Chemistry and Material Science, Shandong Agricultural University, Taian 271018, PR China
| | - Xiangjian Meng
- College of Chemistry and Material Science, Shandong Agricultural University, Taian 271018, PR China
| | - Geoffrey I N Waterhouse
- College of Chemistry and Material Science, Shandong Agricultural University, Taian 271018, PR China; School of Chemical Sciences, The University of Auckland, Auckland 1142, New Zealand
| | - Shiyun Ai
- College of Chemistry and Material Science, Shandong Agricultural University, Taian 271018, PR China.
| |
Collapse
|
40
|
Kaviraj B, Sahoo D. Physics of excitons and their transport in two dimensional transition metal dichalcogenide semiconductors. RSC Adv 2019; 9:25439-25461. [PMID: 35530097 PMCID: PMC9070122 DOI: 10.1039/c9ra03769a] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2019] [Accepted: 07/17/2019] [Indexed: 11/21/2022] Open
Abstract
Two-dimensional (2D) group-VI transition metal dichalcogenide (TMD) semiconductors, such as MoS2, MoSe2, WS2 and others manifest strong light matter coupling and exhibit direct band gaps which lie in the visible and infrared spectral regimes. These properties make them potentially interesting candidates for applications in optics and optoelectronics. The excitons found in these materials are tightly bound and dominate the optical response, even at room temperatures. Large binding energies and unique exciton fine structure make these materials an ideal platform to study exciton behaviors in two-dimensional systems. This review article mainly focuses on studies of mechanisms that control dynamics of excitons in 2D systems – an area where there remains a lack of consensus in spite of extensive research. Firstly, we focus on the kinetics of dark and bright excitons based on a rate equation model and discuss on the role of previous ‘unsuspected’ dark excitons in controlling valley polarization. Intrinsically, dark and bright exciton energy splitting plays a key role in modulating the dynamics. In the second part, we review the excitation energy-dependent possible characteristic relaxation pathways of photoexcited carriers in monolayer and bilayer systems. In the third part, we review the extrinsic factors, in particular the defects that are so prevalent in single layer TMDs, affecting exciton dynamics, transport and non-radiative recombination such as exciton–exciton annihilation. Lastly, the optical response due to pump-induced changes in TMD monolayers have been reviewed using femtosecond pump–probe spectroscopy which facilitates the analysis of underlying physical process just after the excitation. Two-dimensional (2D) group-VI transition metal dichalcogenide (TMD) semiconductors, such as MoS2, MoSe2, WS2 and others manifest strong light matter coupling and exhibit direct band gaps which lie in the visible and infrared spectral regimes.![]()
Collapse
Affiliation(s)
- Bhaskar Kaviraj
- Department of Physics
- School of Natural Sciences
- Shiv Nadar University
- Greater Noida
- India
| | - Dhirendra Sahoo
- Department of Physics
- School of Natural Sciences
- Shiv Nadar University
- Greater Noida
- India
| |
Collapse
|
41
|
Luo Y, Wang S, Ren K, Chou JP, Yu J, Sun Z, Sun M. Transition-metal dichalcogenides/Mg(OH)2 van der Waals heterostructures as promising water-splitting photocatalysts: a first-principles study. Phys Chem Chem Phys 2019; 21:1791-1796. [PMID: 30624443 DOI: 10.1039/c8cp06960c] [Citation(s) in RCA: 94] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We found that the MoS2/Mg(OH)2 and WS2/Mg(OH)2 vdW heterostructures are promising for application in photocatalytic water splitting.
Collapse
Affiliation(s)
- Yi Luo
- School of Materials Science and Engineering
- Southeast University
- Nanjing
- China
| | - Sake Wang
- College of Science
- Jinling Institute of Technology
- Nanjing
- China
| | - Kai Ren
- School of Mechanical Engineering
- Southeast University
- Nanjing
- China
| | - Jyh-Pin Chou
- Department of Mechanical Engineering
- City University of Hong Kong
- Hong Kong 999077
- China
| | - Jin Yu
- School of Materials Science and Engineering
- Southeast University
- Nanjing
- China
| | - Zhengming Sun
- School of Materials Science and Engineering
- Southeast University
- Nanjing
- China
| | - Minglei Sun
- Physical Science and Engineering Division (PSE)
- King Abdullah University of Science and Technology (KAUST)
- Thuwal 23955-6900
- Saudi Arabia
| |
Collapse
|
42
|
Dhakal KP, Kim H, Lee S, Kim Y, Lee J, Ahn JH. Probing the upper band gap of atomic rhenium disulfide layers. LIGHT, SCIENCE & APPLICATIONS 2018; 7:98. [PMID: 30510694 PMCID: PMC6262017 DOI: 10.1038/s41377-018-0100-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 11/04/2018] [Accepted: 11/12/2018] [Indexed: 05/30/2023]
Abstract
Here, we investigate the ultrafast carrier dynamics and electronic states of exfoliated ReS2 films using time-resolved second harmonic generation (TSHG) microscopy and density functional theory (DFT) calculations. The second harmonic generation (SHG) of layers with various thicknesses is probed using a 1.19-eV beam. Up to ~13 nm, a gradual increment is observed, followed by a decrease caused by bulk interferometric light absorption. The addition of a pump pulse tuned to the exciton band gap (1.57 eV) creates a decay-to-rise TSHG profile as a function of the probe delay. The power and thickness dependencies indicate that the electron-hole recombination is mediated by defects and surfaces. The two photon absorptions of 2.38 eV in the excited state that are induced by pumping from 1.57 to 1.72 eV are restricted because these transitions highly correlate with the forbidden d-d intrasubshell orbital transitions. However, the combined usage of a frequency-doubled pump (2.38 eV) with wavelength-variant SHG probes (2.60-2.82 eV) allows us to vividly monitor the variations in TSHG profiles from decay-to-rise to rise-to-decay, which imply the existence of an additional electron absorption state (s-orbital) at an approximate distance of 5.05 eV from the highest occupied molecular orbital states. This observation was critically examined by considering the allowance of each electronic transition and a small upper band gap (~0.5 eV) using modified DFT calculations.
Collapse
Affiliation(s)
- Krishna P. Dhakal
- School of Electrical and Electronic Engineering, Yonsei University, Seoul, 03722 Republic of Korea
| | - Hyunmin Kim
- Companion Diagnostics & Medical Technology Research Group, DGIST, Daegu, 42988 Republic of Korea
| | - Seonwoo Lee
- School of Electrical and Electronic Engineering, Yonsei University, Seoul, 03722 Republic of Korea
| | - Youngjae Kim
- Department of Emerging Materials Science, DGIST, Daegu, 42988 Republic of Korea
| | - JaeDong Lee
- Department of Emerging Materials Science, DGIST, Daegu, 42988 Republic of Korea
| | - Jong-Hyun Ahn
- School of Electrical and Electronic Engineering, Yonsei University, Seoul, 03722 Republic of Korea
| |
Collapse
|
43
|
Li Y, Shi J, Chen H, Wang R, Mi Y, Zhang C, Du W, Zhang S, Liu Z, Zhang Q, Qiu X, Xu H, Liu W, Liu Y, Liu X. The Auger process in multilayer WSe 2 crystals. NANOSCALE 2018; 10:17585-17592. [PMID: 29943785 DOI: 10.1039/c8nr02567c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Multilayer WSe2 with a larger optical density of states and absorbance is regarded as a better candidate than its monolayer counterpart for next generation optoelectronic devices, however insight into carrier dynamics is still lacking. Herein, we experimentally observed an anomalous PL quenching with decreasing temperature for multilayer WSe2. At a low temperature (77 K), the Auger processes govern carrier recombination in multilayer WSe2, which are induced by a phonon bottleneck effect and strong photon absorption, and lead to PL quenching. From transient absorption spectroscopy, two distinct Auger processes are observed: a fast one (1-2 ps) and a slow one (>190 ps), which are caused by two different deep midgap defect-levels in WSe2. Based on the Auger recombination model, these two Auger rates are quantitatively estimated at ∼6.69 (±0.05) × 10-2 and 1.22 (±0.04) × 10-3 cm2 s-1, respectively. Our current observations provide an important supplement for optimizing the optical and electric behaviors in multilayer WSe2 based devices.
Collapse
Affiliation(s)
- Yuanzheng Li
- Division of Nanophotonics, CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
44
|
Chi Z, Chen H, Chen Z, Zhao Q, Chen H, Weng YX. Ultrafast Energy Dissipation via Coupling with Internal and External Phonons in Two-Dimensional MoS 2. ACS NANO 2018; 12:8961-8969. [PMID: 30114918 DOI: 10.1021/acsnano.8b02354] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Atomically thin two-dimensional materials have emerged as a promising system for optoelectronic applications; however, the low quantum yield, mainly caused by nonradiative energy dissipation, has greatly limited practical applications. To reveal the details for nonradiative energy channels, femtosecond pump-probe spectroscopy with a detection wavelength ranging from visible to near-infrared to mid-infrared is performed on few-layer MoS2. With this method, the many-body effects, occupation effects, and phonon dynamics are clearly identified. In particular, thermalization of the MoS2 lattice via electron-phonon scattering is responsible for a redshift of the exciton resonance energy observed within tens to hundreds of picoseconds after photoexcitation, which provides a direct real-time sensor for measuring the change in lattice temperature. We find that the excess energy from the cooling of hot carriers and the formation of bound carriers is efficiently transferred to the internal phonon system within 2 ps, while that from Shockley-Read-Hall recombination (∼9 ps) is mainly dissipated from the MoS2 surfaces to external phonons.
Collapse
Affiliation(s)
- Zhen Chi
- Beijing National Laboratory for Condensed Matter Physics, CAS Key Laboratory of Soft Matter Physics, Institute of Physics , Chinese Academy of Sciences , Beijing 100190 , China
- Center for Quantum Technology Research, School of Physics , Beijing Institute of Technology , Beijing 100081 , China
| | - Huihui Chen
- Department of Materials Physics and Chemistry, Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, School of Materials Science and Engineering , Beijing Institute of Technology Institution , Beijing 100081 , China
| | - Zhuo Chen
- Department of Materials Physics and Chemistry, Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, School of Materials Science and Engineering , Beijing Institute of Technology Institution , Beijing 100081 , China
| | - Qing Zhao
- Center for Quantum Technology Research, School of Physics , Beijing Institute of Technology , Beijing 100081 , China
| | - Hailong Chen
- Beijing National Laboratory for Condensed Matter Physics, CAS Key Laboratory of Soft Matter Physics, Institute of Physics , Chinese Academy of Sciences , Beijing 100190 , China
| | - Yu-Xiang Weng
- Beijing National Laboratory for Condensed Matter Physics, CAS Key Laboratory of Soft Matter Physics, Institute of Physics , Chinese Academy of Sciences , Beijing 100190 , China
- School of Physical Sciences , University of Chinese Academy of Sciences , Beijing 100049 , China
| |
Collapse
|
45
|
Wang H, Li C, Fang P, Zhang Z, Zhang JZ. Synthesis, properties, and optoelectronic applications of two-dimensional MoS 2 and MoS 2-based heterostructures. Chem Soc Rev 2018; 47:6101-6127. [PMID: 30022215 DOI: 10.1039/c8cs00314a] [Citation(s) in RCA: 121] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
As a two-dimensional (2D) material, molybdenum disulfide (MoS2) exhibits unique electronic and optical properties useful for a variety of optoelectronic applications including light harvesting. In this article, we review recent progress in the synthesis, properties and applications of MoS2 and related heterostructures. Heterostructured materials are developed to add more functionality or flexibility compared to single component materials. Our focus is on their novel properties and functionalities as well as emerging applications, especially in the areas of light energy harvesting or conversion. We highlight the correlation between structural properties and other properties including electronic, optical, and dynamic. Whenever appropriate, we also try to provide fundamental insight gained from experimental as well as theoretical studies. Finally, we discuss some current challenges and opportunities in technological applications of MoS2.
Collapse
Affiliation(s)
- Hongmei Wang
- College of Biological, Chemical Sciences and Engineering, Jiaxing University, Jiaxing 314001, China.
| | | | | | | | | |
Collapse
|
46
|
Wang L, Xu C, Li MY, Li LJ, Loh ZH. Unraveling Spatially Heterogeneous Ultrafast Carrier Dynamics of Single-Layer WSe 2 by Femtosecond Time-Resolved Photoemission Electron Microscopy. NANO LETTERS 2018; 18:5172-5178. [PMID: 29969565 DOI: 10.1021/acs.nanolett.8b02103] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Studies of the ultrafast carrier dynamics of transition metal dichalcogenides have employed spatially averaged measurements, which obfuscate the rich variety of dynamics that originate from the structural heterogeneity of these materials. Here, we employ femtosecond time-resolved photoemission electron microscopy (TR-PEEM) with sub-80 nm spatial resolution to image the ultrafast subpicosecond to picosecond carrier dynamics of monolayer tungsten diselenide (WSe2). The dynamics observed following 2.41 eV pump and 3.61 eV probe occurs on two distinct time scales. The 0.1 ps process is assigned to electron cooling via intervalley scattering, whereas the picosecond dynamics is attributed to exciton-exciton annihilation. The 70 fs decay dynamics observed at negative time delay reflects electronic relaxation from the Γ point. Analysis of the TR-PEEM data furnishes the spatial distributions of the various time constants within a single WSe2 flake. The spatial heterogeneity of the lifetime maps is consistent with increased disorder along the edges of the flake and the presence of nanoscale charge puddles in the interior. Our results indicate the need to go beyond spatially averaged time-resolved measurements to understand the influence of structural heterogeneities on the elementary carrier dynamics of two-dimensional materials.
Collapse
Affiliation(s)
- Lin Wang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences , Nanyang Technological University , 21 Nanyang Link , Singapore 637371 , Singapore
| | - Ce Xu
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences , Nanyang Technological University , 21 Nanyang Link , Singapore 637371 , Singapore
| | - Ming-Yang Li
- Physical Sciences and Engineering , King Abdullah University of Science and Technology , Thuwal , 23955-6900 , Kingdom of Saudi Arabia
| | - Lain-Jong Li
- Physical Sciences and Engineering , King Abdullah University of Science and Technology , Thuwal , 23955-6900 , Kingdom of Saudi Arabia
| | - Zhi-Heng Loh
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences , Nanyang Technological University , 21 Nanyang Link , Singapore 637371 , Singapore
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences , Nanyang Technological University , 21 Nanyang Link , Singapore 637371 , Singapore
- Centre for Optical Fibre Technology, The Photonics Institute , Nanyang Technological University , Singapore 639798 , Singapore
| |
Collapse
|
47
|
Zhao S, He D, He J, Zhang X, Yi L, Wang Y, Zhao H. Probing excitons in transition metal dichalcogenides by Drude-like exciton intraband absorption. NANOSCALE 2018; 10:9538-9546. [PMID: 29745949 DOI: 10.1039/c8nr03135e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Understanding excitonic dynamics in two-dimensional semiconducting transition metal dichalcogenides is important for developing their optoelectronic applications. Recently, transient absorption techniques based on resonant excitonic absorption have been used to study various aspects of excitonic dynamics in these materials. The transient absorption in such measurements originates from phase-space state filling, bandgap renormalization, or screening effects. Here we report a new method to probe excitonic dynamics based on exciton intraband absorption. In this Drude-like process, probe photons are absorbed by excitons in their intraband excitation to higher energy states, causing a transient absorption signal. Although the magnitude of the transient absorption is lower than that of the resonant techniques, the new method is less restrictive on the selection of probe wavelength, has a larger linear range, and can provide complementary information on photocarrier dynamics. Using the WS2 monolayer and bulk samples as examples, we show that the new method can probe exciton-exciton annihilation at high densities and reveal exciton formation processes. We also found that the exciton intraband absorption cross section of the WS2 monolayer is on the order of 10-18 cm2.
Collapse
Affiliation(s)
- Siqi Zhao
- Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044, China.
| | | | | | | | | | | | | |
Collapse
|
48
|
Henning A, Sangwan VK, Bergeron H, Balla I, Sun Z, Hersam MC, Lauhon LJ. Charge Separation at Mixed-Dimensional Single and Multilayer MoS 2/Silicon Nanowire Heterojunctions. ACS APPLIED MATERIALS & INTERFACES 2018; 10:16760-16767. [PMID: 29682958 DOI: 10.1021/acsami.8b03133] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Layered two-dimensional (2-D) semiconductors can be combined with other low-dimensional semiconductors to form nonplanar mixed-dimensional van der Waals (vdW) heterojunctions whose charge transport behavior is influenced by the heterojunction geometry, providing a new degree of freedom to engineer device functions. Toward that end, we investigated the photoresponse of Si nanowire/MoS2 heterojunction diodes with scanning photocurrent microscopy and time-resolved photocurrent measurements. Comparison of n-Si/MoS2 isotype heterojunctions with p-Si/MoS2 heterojunction diodes under varying biases shows that the depletion region in the p-n heterojunction promotes exciton dissociation and carrier collection. We measure an instrument-limited response time of 1 μs, which is 10 times faster than the previously reported response times for planar Si/MoS2 devices, highlighting the advantages of the 1-D/2-D heterojunction. Finite element simulations of device models provide a detailed understanding of how the electrostatics affect charge transport in nanowire/vdW heterojunctions and inform the design of future vdW heterojunction photodetectors and transistors.
Collapse
|
49
|
Kumar P, Liu J, Ranjan P, Hu Y, Yamijala SS, Pati SK, Irudayaraj J, Cheng GJ. Alpha Lead Oxide (α-PbO): A New 2D Material with Visible Light Sensitivity. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2018; 14:e1703346. [PMID: 29430851 DOI: 10.1002/smll.201703346] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 12/17/2017] [Indexed: 05/23/2023]
Abstract
Even though transition metal dichalcogenides (TMDCs) are deemed to be novel photonic and optoelectronic 2D materials, the visible band gap being often limited to monolayer, hampers their potential in niche applications due to fabrication challenges. Uncontrollable defects and degraded functionalities at elevated temperature and under extreme environments further restrict their prospects. To address such limitations, the discovery of a new 2D material, α-PbO is reported. Micromechanical as well as sonochemical exfoliation of 2D atomic sheets of α-PbO are demonstrated and its optical behavior is investigated. Spectroscopic investigations indicate layer dependent band gaps. In particular, even multilayered PbO sheets exhibit visible band gap > 2 eV (direct) which is rare among semiconducting 2D materials. The emission lifetime of multilayer PbO atomic sheets is 7 ns (dim light) as compared to the monolayer which gives 2.5 ns lifetime and an intense light. Density functional theory calculations of layer dependent band structure of α-PbO matches well with experimental results. Experimental findings suggest that PbO atomic sheets exhibit hydrophobic nature, thermal robustness, microwave stability, anti-corrosive behaviour and acid resistance. This new low-cost, abundant and robust 2D material is expected to find many applications in the fields of electronics, optoelectronics, sensors, photocatalysis and energy storage.
Collapse
Affiliation(s)
- Prashant Kumar
- Birck Nanotechnology Centre, Purdue University, West Lafayette, IN, 47907, USA
- School of Industrial Engineering, Purdue University, West Lafayette, IN, 47907, USA
- Department of Physics, Indian Institute of Technology, Bihta Campus, Patna, 801103, India
| | - Jing Liu
- Birck Nanotechnology Centre, Purdue University, West Lafayette, IN, 47907, USA
- Bindley Bioscience Centre, Purdue University, West Lafayette, IN, 47907, USA
- Agricultural & Biological Engineering, Purdue University, West Lafayette, IN, 47907, USA
- Department of Physics, School of Science, Indiana University-Purdue University, IN, 46202, USA
| | - Pranay Ranjan
- Department of Physics, Indian Institute of Technology, Bihta Campus, Patna, 801103, India
| | - Yaowu Hu
- Birck Nanotechnology Centre, Purdue University, West Lafayette, IN, 47907, USA
- School of Industrial Engineering, Purdue University, West Lafayette, IN, 47907, USA
- School of Mechanical Engineering, Purdue University, West Lafayette, IN, 47907, USA
- Department of Mechanical and aerospace Engineering, University of Buffalo, Buffalo, NY, 14260, USA
| | - Sharma Srkc Yamijala
- Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, 560064, India
- Department of Chemistry, University of Rochester, Rochester, NY, 14620, USA
| | - Swapan K Pati
- Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, 560064, India
| | - Joseph Irudayaraj
- Birck Nanotechnology Centre, Purdue University, West Lafayette, IN, 47907, USA
- Bindley Bioscience Centre, Purdue University, West Lafayette, IN, 47907, USA
- Agricultural & Biological Engineering, Purdue University, West Lafayette, IN, 47907, USA
- University of Illinois at Urbana-Champaign, Urbana, IL, 61820, USA
| | - Gary J Cheng
- Birck Nanotechnology Centre, Purdue University, West Lafayette, IN, 47907, USA
- School of Industrial Engineering, Purdue University, West Lafayette, IN, 47907, USA
- School of Mechanical Engineering, Purdue University, West Lafayette, IN, 47907, USA
| |
Collapse
|
50
|
Kim YC, Nguyen VT, Lee S, Park JY, Ahn YH. Evaluation of Transport Parameters in MoS 2/Graphene Junction Devices Fabricated by Chemical Vapor Deposition. ACS APPLIED MATERIALS & INTERFACES 2018; 10:5771-5778. [PMID: 29355012 DOI: 10.1021/acsami.7b16177] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We demonstrated imaging of the depletion layer in a MoS2/graphene heterojunction fabricated by chemical vapor deposition and obtained their transport parameters such as diffusion length, lifetime, and mobility by using scanning photocurrent microscopy (SPCM). The device exhibited a n-type operation, which was determined by the MoS2 layer with a lower mobility. The SPCM revealed the presence of the depletion layer at the heterojunction, whereas graphene provided an excellent electrical contact for the MoS2 layer without resulting in a rectifying behavior, even if they were anchored within a very short range. The polarity of the photocurrent signal switched when we applied a drain-source bias voltage, from which we extracted the potential barrier at the junction. More importantly, a bias-dependent SPCM allowed us to simultaneously record the diffusion lengths of both majority and minority carriers for the respective MoS2 and graphene layers. By combining the diffusion lengths with the lifetimes measured by femtosecond SPCM, we determined the electron and hole mobilities in each layer, from which we found that the electron mobility (160 cm2 V-1 s-1) was higher than the hole mobility (80 cm2 V-1 s-1) in MoS2, whereas the hole mobility (15 000 cm2 V-1 s-1) was relatively higher in graphene.
Collapse
Affiliation(s)
- Young Chul Kim
- Department of Physics and Department of Energy Systems Research, Ajou University , Suwon 16499, Korea
| | - Van Tu Nguyen
- Department of Physics and Department of Energy Systems Research, Ajou University , Suwon 16499, Korea
| | - Soonil Lee
- Department of Physics and Department of Energy Systems Research, Ajou University , Suwon 16499, Korea
| | - Ji-Yong Park
- Department of Physics and Department of Energy Systems Research, Ajou University , Suwon 16499, Korea
| | - Yeong Hwan Ahn
- Department of Physics and Department of Energy Systems Research, Ajou University , Suwon 16499, Korea
| |
Collapse
|