51
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Mayorga EJ, Kvidera SK, Horst EA, Al-Qaisi MA, Dickson MJ, Seibert JT, Lei S, Rambo ZJ, Wilson ME, Baumgard LH. 325 Effects of zinc amino acid complex on biomarkers of gut integrity and metabolism during heat stress and a following recovery period in growing pigs. J Anim Sci 2017. [DOI: 10.2527/asasmw.2017.325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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52
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Man MKL, Margiolakis A, Deckoff-Jones S, Harada T, Wong EL, Krishna MBM, Madéo J, Winchester A, Lei S, Vajtai R, Ajayan PM, Dani KM. Imaging the motion of electrons across semiconductor heterojunctions. NATURE NANOTECHNOLOGY 2017; 12:36-40. [PMID: 27723731 DOI: 10.1038/nnano.2016.183] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 08/22/2016] [Indexed: 05/22/2023]
Abstract
Technological progress since the late twentieth century has centred on semiconductor devices, such as transistors, diodes and solar cells. At the heart of these devices is the internal motion of electrons through semiconductor materials due to applied electric fields or by the excitation of photocarriers. Imaging the motion of these electrons would provide unprecedented insight into this important phenomenon, but requires high spatial and temporal resolution. Current studies of electron dynamics in semiconductors are generally limited by the spatial resolution of optical probes, or by the temporal resolution of electronic probes. Here, by combining femtosecond pump-probe techniques with spectroscopic photoemission electron microscopy, we imaged the motion of photoexcited electrons from high-energy to low-energy states in a type-II 2D InSe/GaAs heterostructure. At the instant of photoexcitation, energy-resolved photoelectron images revealed a highly non-equilibrium distribution of photocarriers in space and energy. Thereafter, in response to the out-of-equilibrium photocarriers, we observed the spatial redistribution of charges, thus forming internal electric fields, bending the semiconductor bands, and finally impeding further charge transfer. By assembling images taken at different time-delays, we produced a movie lasting a few trillionths of a second of the electron-transfer process in the photoexcited type-II heterostructure-a fundamental phenomenon in semiconductor devices such as solar cells. Quantitative analysis and theoretical modelling of spatial variations in the movie provide insight into future solar cells, 2D materials and other semiconductor devices.
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53
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Najmaei S, Lei S, Burke RA, Nichols BM, George A, Ajayan PM, Franklin AD, Lou J, Dubey M. Enabling Ultrasensitive Photo-detection Through Control of Interface Properties in Molybdenum Disulfide Atomic Layers. Sci Rep 2016; 6:39465. [PMID: 27995992 PMCID: PMC5172306 DOI: 10.1038/srep39465] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 11/07/2016] [Indexed: 12/14/2022] Open
Abstract
The interfaces in devices made of two-dimensional materials such as MoS2 can effectively control their optoelectronic performance. However, the extent and nature of these deterministic interactions are not fully understood. Here, we investigate the role of substrate interfaces on the photodetector properties of MoS2 devices by studying its photocurrent properties on both SiO2 and self-assembled monolayer-modified substrates. Results indicate that while the photoresponsivity of the devices can be enhanced through control of device interfaces, response times are moderately compromised. We attribute this trade-off to the changes in the electrical contact resistance at the device metal-semiconductor interface. We demonstrate that the formation of charge carrier traps at the interface can dominate the device photoresponse properties. The capture and emission rates of deeply trapped charge carriers in the substrate-semiconductor-metal regions are strongly influenced by exposure to light and can dynamically dope the contact regions and thus perturb the photodetector properties. As a result, interface-modified photodetectors have significantly lower dark-currents and higher on-currents. Through appropriate interfacial design, a record high device responsivity of 4.5 × 103 A/W at 7 V is achieved, indicative of the large signal gain in the devices and exemplifying an important design strategy that enables highly responsive two-dimensional photodetectors.
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54
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Repka M, Kole T, Wu B, Tong M, Lei S, Suy S, Dritschilo A, Collins S. Effect of Dose to the Bladder Wall and Trigone on Late Urinary Flare Following Definitive Stereotactic Body Radiation Therapy (SBRT) for Localized Prostate Cancer. Int J Radiat Oncol Biol Phys 2016. [DOI: 10.1016/j.ijrobp.2016.06.302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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55
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Li B, Gong Y, Hu Z, Brunetto G, Yang Y, Ye G, Zhang Z, Lei S, Jin Z, Bianco E, Zhang X, Wang W, Lou J, Galvão DS, Tang M, Yakobson BI, Vajtai R, Ajayan PM. Solid-Vapor Reaction Growth of Transition-Metal Dichalcogenide Monolayers. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201604445] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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56
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Li B, Gong Y, Hu Z, Brunetto G, Yang Y, Ye G, Zhang Z, Lei S, Jin Z, Bianco E, Zhang X, Wang W, Lou J, Galvão DS, Tang M, Yakobson BI, Vajtai R, Ajayan PM. Solid-Vapor Reaction Growth of Transition-Metal Dichalcogenide Monolayers. Angew Chem Int Ed Engl 2016; 55:10656-61. [DOI: 10.1002/anie.201604445] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Indexed: 11/11/2022]
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57
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He X, Gao W, Xie L, Li B, Zhang Q, Lei S, Robinson JM, Hároz EH, Doorn SK, Wang W, Vajtai R, Ajayan PM, Adams WW, Hauge RH, Kono J. Wafer-scale monodomain films of spontaneously aligned single-walled carbon nanotubes. NATURE NANOTECHNOLOGY 2016; 11:633-8. [PMID: 27043199 DOI: 10.1038/nnano.2016.44] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2015] [Accepted: 02/19/2016] [Indexed: 05/02/2023]
Abstract
The one-dimensional character of electrons, phonons and excitons in individual single-walled carbon nanotubes leads to extremely anisotropic electronic, thermal and optical properties. However, despite significant efforts to develop ways to produce large-scale architectures of aligned nanotubes, macroscopic manifestations of such properties remain limited. Here, we show that large (>cm(2)) monodomain films of aligned single-walled carbon nanotubes can be prepared using slow vacuum filtration. The produced films are globally aligned within ±1.5° (a nematic order parameter of ∼1) and are highly packed, containing 1 × 10(6) nanotubes in a cross-sectional area of 1 μm(2). The method works for nanotubes synthesized by various methods, and film thickness is controllable from a few nanometres to ∼100 nm. We use the approach to create ideal polarizers in the terahertz frequency range and, by combining the method with recently developed sorting techniques, highly aligned and chirality-enriched nanotube thin-film devices. Semiconductor-enriched devices exhibit polarized light emission and polarization-dependent photocurrent, as well as anisotropic conductivities and transistor action with high on/off ratios.
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58
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He Y, Sobhani A, Lei S, Zhang Z, Gong Y, Jin Z, Zhou W, Yang Y, Zhang Y, Wang X, Yakobson B, Vajtai R, Halas NJ, Li B, Xie E, Ajayan P. Layer Engineering of 2D Semiconductor Junctions. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2016; 28:5126-32. [PMID: 27136275 DOI: 10.1002/adma.201600278] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2016] [Revised: 02/29/2016] [Indexed: 05/28/2023]
Abstract
A new concept for junction fabrication by connecting multiple regions with varying layer thicknesses, based on the thickness dependence, is demonstrated. This type of junction is only possible in super-thin-layered 2D materials, and exhibits similar characteristics as p-n junctions. Rectification and photovoltaic effects are observed in chemically homogeneous MoSe2 junctions between domains of different thicknesses.
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59
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Cadafalch Gazquez G, Lei S, George A, Gullapalli H, Boukamp BA, Ajayan PM, Ten Elshof JE. Low-Cost, Large-Area, Facile, and Rapid Fabrication of Aligned ZnO Nanowire Device Arrays. ACS APPLIED MATERIALS & INTERFACES 2016; 8:13466-71. [PMID: 27173007 DOI: 10.1021/acsami.6b01594] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Well aligned nanowires of ZnO have been made with an electrospinning technique using zinc acetate precursor solutions. Employment of two connected parallel collector plates with a separating gap of 4 cm resulted in a very high degree of nanowire alignment. By adjusting the process parameters, the deposition density of the wires could be controlled. Field effect transistors were prepared by depositing wires between two gold electrodes on top of a heavily doped Si substrate covered with a 300 nm oxide layer. These devices showed good FET characteristics and photosensitivity under UV-illumination. The method provides a fast and scalable fabrication route for functional nanowire arrays with a high degree of alignment and control over nanowire spacing.
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60
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He Y, Yang Y, Zhang Z, Gong Y, Zhou W, Hu Z, Ye G, Zhang X, Bianco E, Lei S, Jin Z, Zou X, Yang Y, Zhang Y, Xie E, Lou J, Yakobson B, Vajtai R, Li B, Ajayan P. Strain-Induced Electronic Structure Changes in Stacked van der Waals Heterostructures. NANO LETTERS 2016; 16:3314-20. [PMID: 27120401 DOI: 10.1021/acs.nanolett.6b00932] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Vertically stacked van der Waals heterostructures composed of compositionally different two-dimensional atomic layers give rise to interesting properties due to substantial interactions between the layers. However, these interactions can be easily obscured by the twisting of atomic layers or cross-contamination introduced by transfer processes, rendering their experimental demonstration challenging. Here, we explore the electronic structure and its strain dependence of stacked MoSe2/WSe2 heterostructures directly synthesized by chemical vapor deposition, which unambiguously reveal strong electronic coupling between the atomic layers. The direct and indirect band gaps (1.48 and 1.28 eV) of the heterostructures are measured to be lower than the band gaps of individual MoSe2 (1.50 eV) and WSe2 (1.60 eV) layers. Photoluminescence measurements further show that both the direct and indirect band gaps undergo redshifts with applied tensile strain to the heterostructures, with the change of the indirect gap being particularly more sensitive to strain. This demonstration of strain engineering in van der Waals heterostructures opens a new route toward fabricating flexible electronics.
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61
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Lei S, Wang X, Li B, Kang J, He Y, George A, Ge L, Gong Y, Dong P, Jin Z, Brunetto G, Chen W, Lin ZT, Baines R, Galvão DS, Lou J, Barrera E, Banerjee K, Vajtai R, Ajayan P. Surface functionalization of two-dimensional metal chalcogenides by Lewis acid-base chemistry. NATURE NANOTECHNOLOGY 2016; 11:465-71. [PMID: 26828848 DOI: 10.1038/nnano.2015.323] [Citation(s) in RCA: 97] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 12/10/2015] [Indexed: 05/27/2023]
Abstract
Precise control of the electronic surface states of two-dimensional (2D) materials could improve their versatility and widen their applicability in electronics and sensing. To this end, chemical surface functionalization has been used to adjust the electronic properties of 2D materials. So far, however, chemical functionalization has relied on lattice defects and physisorption methods that inevitably modify the topological characteristics of the atomic layers. Here we make use of the lone pair electrons found in most of 2D metal chalcogenides and report a functionalization method via a Lewis acid-base reaction that does not alter the host structure. Atomic layers of n-type InSe react with Ti(4+) to form planar p-type [Ti(4+)n(InSe)] coordination complexes. Using this strategy, we fabricate planar p-n junctions on 2D InSe with improved rectification and photovoltaic properties, without requiring heterostructure growth procedures or device fabrication processes. We also show that this functionalization approach works with other Lewis acids (such as B(3+), Al(3+) and Sn(4+)) and can be applied to other 2D materials (for example MoS2, MoSe2). Finally, we show that it is possible to use Lewis acid-base chemistry as a bridge to connect molecules to 2D atomic layers and fabricate a proof-of-principle dye-sensitized photosensing device.
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62
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Mayorga EJ, Stoakes SK, Seibert JT, Horst EA, Abuajamieh M, Lei S, Ochoa L, Kremer B, Baumgard LH. 306 Effects of dietary chromium propionate during heat stress on finishing pigs. J Anim Sci 2016. [DOI: 10.2527/msasas2016-306] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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63
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Deckoff-Jones S, Zhang J, Petoukhoff CE, Man MKL, Lei S, Vajtai R, Ajayan PM, Talbayev D, Madéo J, Dani KM. Observing the interplay between surface and bulk optical nonlinearities in thin van der Waals crystals. Sci Rep 2016; 6:22620. [PMID: 26936437 PMCID: PMC4776178 DOI: 10.1038/srep22620] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Accepted: 02/17/2016] [Indexed: 01/28/2023] Open
Abstract
Van der Waals materials, existing in a range of thicknesses from monolayer to bulk, allow for interplay between surface and bulk nonlinearities, which otherwise dominate only at atomically-thin or bulk extremes, respectively. Here, we observe an unexpected peak in intensity of the generated second harmonic signal versus the thickness of Indium Selenide crystals, in contrast to the quadratic increase expected from thin crystals. We explain this by interference effects between surface and bulk nonlinearities, which offer a new handle on engineering the nonlinear optical response of 2D materials and their heterostructures.
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64
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Dong P, Chipara AC, Loya P, Yang Y, Ge L, Lei S, Li B, Brunetto G, Machado LD, Hong L, Wang Q, Yang B, Guo H, Ringe E, Galvao DS, Vajtai R, Chipara M, Tang M, Lou J, Ajayan PM. Solid-Liquid Self-Adaptive Polymeric Composite. ACS APPLIED MATERIALS & INTERFACES 2016; 8:2142-2147. [PMID: 26720058 DOI: 10.1021/acsami.5b10667] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
A solid-liquid self-adaptive composite (SAC) is synthesized using a simple mixing-evaporation protocol, with poly(dimethylsiloxane) (PDMS) and poly(vinylidene fluoride) (PVDF) as active constituents. SAC exists as a porous solid containing a near equivalent distribution of the solid (PVDF)-liquid (PDMS) phases, with the liquid encapsulated and stabilized within a continuous solid network percolating throughout the structure. The pores, liquid, and solid phases form a complex hierarchical structure, which offers both mechanical robustness and a significant structural adaptability under external forces. SAC exhibits attractive self-healing properties during tension, and demonstrates reversible self-stiffening properties under compression with a maximum of 7-fold increase seen in the storage modulus. In a comparison to existing self-healing and self-stiffening materials, SAC offers distinct advantages in the ease of fabrication, high achievable storage modulus, and reversibility. Such materials could provide a new class of adaptive materials system with multifunctionality, tunability, and scale-up potentials.
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65
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Siqian L, Lei S, Ying L. Development of a cellular biosensor system for genotoxicity detection based on Trp53 promoter. Hum Exp Toxicol 2015; 35:1102-7. [PMID: 26721909 DOI: 10.1177/0960327115621364] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
OBJECTIVE To develop a mouse cell biosensor system for the high-throughput genotoxicity detection of chemicals, such as environmental pollutants. METHOD We developed a novel reporter vector pGL4-GFP, wherein the firefly luciferase reporter gene in the pGL4.82 vector was replaced by the green fluorescent protein (GFP) gene from the pAcGFP1-N1 vector. To construct the reporter pGL4-p53-GFP (p53 promoter linked to GFP), a fragment containing the p53 gene promoter was generated by amplifying a region from -481 to +180 of mouse genomic DNA isolated from mouse tail tissue. We developed a mouse cell biosensor system for the high-throughput genotoxicity detection of new drugs by stably integrating the reporter plasmid of pGL4-p53-GFP into the mouse embryonic fibroblast cells. Various genotoxic agents were used to treat this biosensor system. The resulting fluorescence was directly observed under a fluorescence microscope, and the GFP protein level was measured through Western blot analysis. RESULT The biosensor system was treated with genotoxic agents, such as doxorubicin, cyclophosphamide, and benzo(a)pyrene. The GFP protein expression was significantly increased in cells exposed to genotoxic agents but negatively responded to the non-genotoxic agent dimethyl sulfoxide, thereby proving the specificity and sensitivity of the biosensor system. CONCLUSION This novel in vitro biosensor system can be especially useful in genotoxicity detection.
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66
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Paydar I, Cyr R, Yung T, Lei S, Collins B, Chen L, Suy S, Dritschilo A, Lynch J, Collins S. Proctitis One Week After Stereotactic Body Radiation Therapy for Prostate Cancer: Implications for Clinical Trial Design. Int J Radiat Oncol Biol Phys 2015. [DOI: 10.1016/j.ijrobp.2015.07.1788] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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67
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Repka M, Kole T, Wu B, Lei S, Suy S, Dritschilo A, Collins S. Predictors of Acute Urinary Flare Following Stereotactic Body Radiation Therapy (SBRT) in the Definitive Treatment of Localized Prostate Cancer. Int J Radiat Oncol Biol Phys 2015. [DOI: 10.1016/j.ijrobp.2015.07.431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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68
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Jin Z, Owour P, Lei S, Ge L. Graphene, graphene quantum dots and their applications in optoelectronics. Curr Opin Colloid Interface Sci 2015. [DOI: 10.1016/j.cocis.2015.11.007] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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69
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Gong Y, Lei S, Ye G, Li B, He Y, Keyshar K, Zhang X, Wang Q, Lou J, Liu Z, Vajtai R, Zhou W, Ajayan PM. Two-Step Growth of Two-Dimensional WSe2/MoSe2 Heterostructures. NANO LETTERS 2015; 15:6135-41. [PMID: 26237631 DOI: 10.1021/acs.nanolett.5b02423] [Citation(s) in RCA: 209] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Two dimensional (2D) materials have attracted great attention due to their unique properties and atomic thickness. Although various 2D materials have been successfully synthesized with different optical and electrical properties, a strategy for fabricating 2D heterostructures must be developed in order to construct more complicated devices for practical applications. Here we demonstrate for the first time a two-step chemical vapor deposition (CVD) method for growing transition-metal dichalcogenide (TMD) heterostructures, where MoSe2 was synthesized first and followed by an epitaxial growth of WSe2 on the edge and on the top surface of MoSe2. Compared to previously reported one-step growth methods, this two-step growth has the capability of spatial and size control of each 2D component, leading to much larger (up to 169 μm) heterostructure size, and cross-contamination can be effectively minimized. Furthermore, this two-step growth produces well-defined 2H and 3R stacking in the WSe2/MoSe2 bilayer regions and much sharper in-plane interfaces than the previously reported MoSe2/WSe2 heterojunctions obtained from one-step growth methods. The resultant heterostructures with WSe2/MoSe2 bilayer and the exposed MoSe2 monolayer display rectification characteristics of a p-n junction, as revealed by optoelectronic tests, and an internal quantum efficiency of 91% when functioning as a photodetector. A photovoltaic effect without any external gates was observed, showing incident photon to converted electron (IPCE) efficiencies of approximately 0.12%, providing application potential in electronics and energy harvesting.
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70
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Li B, Shi G, Lei S, He Y, Gao W, Gong Y, Ye G, Zhou W, Keyshar K, Hao J, Dong P, Ge L, Lou J, Kono J, Vajtai R, Ajayan PM. 3D Band Diagram and Photoexcitation of 2D-3D Semiconductor Heterojunctions. NANO LETTERS 2015; 15:5919-5925. [PMID: 26280193 DOI: 10.1021/acs.nanolett.5b02012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The emergence of a rich variety of two-dimensional (2D) layered semiconductor materials has enabled the creation of atomically thin heterojunction devices. Junctions between atomically thin 2D layers and 3D bulk semiconductors can lead to junctions that are fundamentally electronically different from the covalently bonded conventional semiconductor junctions. Here we propose a new 3D band diagram for the heterojunction formed between n-type monolayer MoS2 and p-type Si, in which the conduction and valence band-edges of the MoS2 monolayer are drawn for both stacked and in-plane directions. This new band diagram helps visualize the flow of charge carriers inside the device in a 3D manner. Our detailed wavelength-dependent photocurrent measurements fully support the diagrams and unambiguously show that the band alignment is type I for this 2D-3D heterojunction. Photogenerated electron-hole pairs in the atomically thin monolayer are separated and driven by an external bias and control the "on/off" states of the junction photodetector device. Two photoresponse regimes with fast and slow relaxation are also revealed in time-resolved photocurrent measurements, suggesting the important role played by charge trap states.
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71
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Mathews I, Abdullaev A, Lei S, Enright R, Wallace MJ, Donegan JF. Reducing thermal crosstalk in ten-channel tunable slotted-laser arrays. OPTICS EXPRESS 2015; 23:23380-23393. [PMID: 26368439 DOI: 10.1364/oe.23.023380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Given the tight constraints on the wavelength stability of sources in optical networks, the thermal crosstalk between operating devices in a ten-channel thermally-tunable slotted laser array for DWDM applications has been investigated. It was found experimentally the current standard thermal solution with the laser array chip mounted on an AlN carrier does not allow for wavelength stability of ± 25 GHz ( ± 2 K) with a temperature rise of 5 K measured in a device with 100 mA (CW) applied to a neighbouring laser (device spacing = 360 µm). A combined experimental/numerical approach revealed solid state submounts comprising diamond or highly ordered pyrolytic graphite are inadequate to reduce crosstalk below an allowable level. Numerical simulations of advanced cooling technologies reveal a microfluidic enabled substrate would reduce thermal crosstalk between operational devices on the chip to acceptable levels. Critically our simulations show this reduced crosstalk is not at the expense of device tunability as the thermal resistance of individual lasers remains similar for the base and microfluidic cases.
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Li B, He Y, Lei S, Najmaei S, Gong Y, Wang X, Zhang J, Ma L, Yang Y, Hong S, Hao J, Shi G, George A, Keyshar K, Zhang X, Dong P, Ge L, Vajtai R, Lou J, Jung YJ, Ajayan PM. Scalable Transfer of Suspended Two-Dimensional Single Crystals. NANO LETTERS 2015; 15:5089-5097. [PMID: 26177185 DOI: 10.1021/acs.nanolett.5b01210] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Large-scale suspended architectures of various two-dimensional (2D) materials (MoS2, MoSe2, WS2, and graphene) are demonstrated on nanoscale patterned substrates with different physical and chemical surface properties, such as flexible polymer substrates (polydimethylsiloxane), rigid Si substrates, and rigid metal substrates (Au/Ag). This transfer method represents a generic, fast, clean, and scalable technique to suspend 2D atomic layers. The underlying principle behind this approach, which employs a capillary-force-free wet-contact printing method, was studied by characterizing the nanoscale solid-liquid-vapor interface of 2D layers with respect to different substrates. As a proof-of-concept, a photodetector of suspended MoS2 has been demonstrated with significantly improved photosensitivity. This strategy could be extended to several other 2D material systems and open the pathway toward better optoelectronic and nanoelectromechnical systems.
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Lei S, Wen F, Ge L, Najmaei S, George A, Gong Y, Gao W, Jin Z, Li B, Lou J, Kono J, Vajtai R, Ajayan P, Halas NJ. An Atomically Layered InSe Avalanche Photodetector. NANO LETTERS 2015; 15:3048-55. [PMID: 25822539 DOI: 10.1021/acs.nanolett.5b00016] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Atomically thin photodetectors based on 2D materials have attracted great interest due to their potential as highly energy-efficient integrated devices. However, photoinduced carrier generation in these media is relatively poor due to low optical absorption, limiting device performance. Current methods for overcoming this problem, such as reducing contact resistances or back gating, tend to increase dark current and suffer slow response times. Here, we realize the avalanche effect in a 2D material-based photodetector and show that avalanche multiplication can greatly enhance the device response of an ultrathin InSe-based photodetector. This is achieved by exploiting the large Schottky barrier formed between InSe and Al electrodes, enabling the application of a large bias voltage. Plasmonic enhancement of the photosensitivity, achieved by patterning arrays of Al nanodisks onto the InSe layer, further improves device efficiency. With an external quantum efficiency approaching 866%, a dark current in the picoamp range, and a fast response time of 87 μs, this atomic layer device exhibits multiple significant advances in overall performance for this class of devices.
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Abuajamieh M, Laughlin E, Lei S, Stoakes S, Mayorga E, Seibert J, Nolan E, Sanz‐Fernandez M, Ross J, Selsby J, Rhoads R, Baumgard L. The Effects of Recovery Time from Heat Stress on Circulating Bioenergetic Variables and Biomarkers of Leaky Gut. FASEB J 2015. [DOI: 10.1096/fasebj.29.1_supplement.lb365] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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75
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Testroet E, Sherman P, Testroet A, Yoder C, Lei S, Reynolds C, O'Neil M, Baas T, Beitz D. Modeling of Hypertrophy and Hyperplasia in Porcine Adipose Tissue. FASEB J 2015. [DOI: 10.1096/fasebj.29.1_supplement.254.5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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