1
|
Dong C, Lu LS, Lin YC, Robinson JA. Air-Stable, Large-Area 2D Metals and Semiconductors. ACS NANOSCIENCE AU 2024; 4:115-127. [PMID: 38644964 PMCID: PMC11027125 DOI: 10.1021/acsnanoscienceau.3c00047] [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: 09/18/2023] [Revised: 12/16/2023] [Accepted: 12/18/2023] [Indexed: 04/23/2024]
Abstract
Two-dimensional (2D) materials are popular for fundamental physics study and technological applications in next-generation electronics, spintronics, and optoelectronic devices due to a wide range of intriguing physical and chemical properties. Recently, the family of 2D metals and 2D semiconductors has been expanding rapidly because they offer properties once unknown to us. One of the challenges to fully access their properties is poor stability in ambient conditions. In the first half of this Review, we briefly summarize common methods of preparing 2D metals and highlight some recent approaches for making air-stable 2D metals. Additionally, we introduce the physicochemical properties of some air-stable 2D metals recently explored. The second half discusses the air stability and oxidation mechanisms of 2D transition metal dichalcogenides and some elemental 2D semiconductors. Their air stability can be enhanced by optimizing growth temperature, substrates, and precursors during 2D material growth to improve material quality, which will be discussed. Other methods, including doping, postgrowth annealing, and encapsulation of insulators that can suppress defects and isolate the encapsulated samples from the ambient environment, will be reviewed.
Collapse
Affiliation(s)
- Chengye Dong
- 2-Dimensional
Crystal Consortium, The Pennsylvania State
University, University
Park, Pennsylvania 16802, United States
| | - Li-Syuan Lu
- Department
of Materials Science and Engineering, The
Pennsylvania State University, University Park, Pennsylvania 16802, 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 300, Taiwan
| | - Joshua A. Robinson
- 2-Dimensional
Crystal Consortium, The Pennsylvania State
University, University
Park, Pennsylvania 16802, United States
- Department
of Materials Science and Engineering, The
Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Center
for Atomically Thin Multifunctional Coatings, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| |
Collapse
|
2
|
Norimatsu W. A Review on Carrier Mobilities of Epitaxial Graphene on Silicon Carbide. MATERIALS (BASEL, SWITZERLAND) 2023; 16:7668. [PMID: 38138815 PMCID: PMC10744437 DOI: 10.3390/ma16247668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 12/11/2023] [Accepted: 12/14/2023] [Indexed: 12/24/2023]
Abstract
Graphene growth by thermal decomposition of silicon carbide (SiC) is a technique that produces wafer-scale, single-orientation graphene on an insulating substrate. It is often referred to as epigraphene, and has been thought to be suitable for electronics applications. In particular, high-frequency devices for communication technology or large quantum Hall plateau for metrology applications using epigraphene are expected, which require high carrier mobility. However, the carrier mobility of as-grown epigraphene exhibit the relatively low values of about 1000 cm2/Vs. Fortunately, we can hope to improve this situation by controlling the electronic state of epigraphene by modifying the surface and interface structures. In this paper, the mobility of epigraphene and the factors that govern it will be described, followed by a discussion of attempts that have been made to improve mobility in this field. These understandings are of great importance for next-generation high-speed electronics using graphene.
Collapse
Affiliation(s)
- Wataru Norimatsu
- Faculty of Science and Engineering, Waseda University, Tokyo 169-8555, Japan
| |
Collapse
|
3
|
Liu Z, Hinaut A, Peeters S, Scherb S, Meyer E, Righi MC, Glatzel T. Reconstruction of a 2D layer of KBr on Ir(111) and electromechanical alteration by graphene. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2021; 12:432-439. [PMID: 34104621 PMCID: PMC8144921 DOI: 10.3762/bjnano.12.35] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 04/17/2021] [Indexed: 06/12/2023]
Abstract
A novel reconstruction of a two-dimensional layer of KBr on an Ir(111) surface is observed by high-resolution noncontact atomic force microscopy and verified by density functional theory (DFT). The observed KBr structure is oriented along the main directions of the Ir(111) surface, but forms a characteristic double-line pattern. Comprehensive calculations by DFT, taking into account the observed periodicities, resulted in a new low-energy reconstruction. However, it is fully relaxed into a common cubic structure when a monolayer of graphene is located between substrate and KBr. By using Kelvin probe force microscopy, the work functions of the reconstructed and the cubic configuration of KBr were measured and indicate, in accordance with the DFT calculations, a difference of nearly 900 meV. The difference is due to the strong interaction and local charge displacement of the K+/Br- ions and the Ir(111) surface, which are reduced by the decoupling effect of graphene, thus yielding different electrical and mechanical properties of the top KBr layer.
Collapse
Affiliation(s)
- Zhao Liu
- Department of Physics, University of Basel, 4056 Basel, Switzerland
| | - Antoine Hinaut
- Department of Physics, University of Basel, 4056 Basel, Switzerland
| | - Stefan Peeters
- Department of Physics and Astronomy, University of Bologna, 40127 Bologna, Italy
| | - Sebastian Scherb
- Department of Physics, University of Basel, 4056 Basel, Switzerland
| | - Ernst Meyer
- Department of Physics, University of Basel, 4056 Basel, Switzerland
| | - Maria Clelia Righi
- Department of Physics and Astronomy, University of Bologna, 40127 Bologna, Italy
| | - Thilo Glatzel
- Department of Physics, University of Basel, 4056 Basel, Switzerland
| |
Collapse
|
4
|
Briggs N, Gebeyehu ZM, Vera A, Zhao T, Wang K, De La Fuente Duran A, Bersch B, Bowen T, Knappenberger KL, Robinson JA. Epitaxial graphene/silicon carbide intercalation: a minireview on graphene modulation and unique 2D materials. NANOSCALE 2019; 11:15440-15447. [PMID: 31393495 DOI: 10.1039/c9nr03721g] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Intercalation of atomic species through epitaxial graphene on silicon carbide began only a few years following its initial report in 2004. The impact of intercalation on the electronic properties of the graphene is well known; however, the intercalant itself can also exhibit intriguing properties not found in nature. This realization has inspired new interest in epitaxial graphene/silicon carbide (EG/SiC) intercalation, where the scope of the technique extends beyond modulation of graphene properties to the creation of new 2D forms of 3D materials. The mission of this minireview is to provide a concise introduction to EG/SiC intercalation and to demonstrate a simplified approach to EG/SiC intercalation. We summarize the primary techniques used to achieve and characterize EG/SiC intercalation, and show that thermal evaporation-based methods can effectively substitute for more complex synthesis techniques, enabling large-scale intercalation of non-refractory metals and compounds including two-dimensional silver (2D-Ag) and gallium nitride (2D-GaNx).
Collapse
Affiliation(s)
- Natalie Briggs
- Department of Materials Science & Engineering, Pennsylvania State University, University Park, PA 16802, USA. and Center for 2-Dimensional and Layered Materials, Pennsylvania State University, University Park, PA 16802, USA and 2-Dimensional Crystal Consortium Materials Innovation Platform, Pennsylvania State University, University Park, PA 16802, USA
| | - Zewdu M Gebeyehu
- Department of Materials Science & Engineering, Pennsylvania State University, University Park, PA 16802, USA. and Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, The Barcelona Institute of Science and Technology (BIST), Campus UAB, Bellaterra, Barcelona, Spain and Universitat Autònoma de Barcelona (UAB), Bellaterra, Spain
| | - Alexander Vera
- Department of Materials Science & Engineering, Pennsylvania State University, University Park, PA 16802, USA. and Center for 2-Dimensional and Layered Materials, Pennsylvania State University, University Park, PA 16802, USA
| | - Tian Zhao
- Department of Chemistry, Pennsylvania State University, University Park, PA 16802, USA
| | - Ke Wang
- Materials Characterization Laboratory, University Park, PA 16802, USA
| | - Ana De La Fuente Duran
- Department of Materials Science & Engineering, Pennsylvania State University, University Park, PA 16802, USA.
| | - Brian Bersch
- Department of Materials Science & Engineering, Pennsylvania State University, University Park, PA 16802, USA. and Center for 2-Dimensional and Layered Materials, Pennsylvania State University, University Park, PA 16802, USA
| | - Timothy Bowen
- Department of Materials Science & Engineering, Pennsylvania State University, University Park, PA 16802, USA. and Center for 2-Dimensional and Layered Materials, Pennsylvania State University, University Park, PA 16802, USA
| | | | - Joshua A Robinson
- Department of Materials Science & Engineering, Pennsylvania State University, University Park, PA 16802, USA. and Center for 2-Dimensional and Layered Materials, Pennsylvania State University, University Park, PA 16802, USA and 2-Dimensional Crystal Consortium Materials Innovation Platform, Pennsylvania State University, University Park, PA 16802, USA and Center for Atomically-Thin Multifunctional Coatings, Pennsylvania State University, University Park, PA 16802, USA
| |
Collapse
|
5
|
An efficient Terahertz rectifier on the graphene/SiC materials platform. Sci Rep 2019; 9:11205. [PMID: 31371741 PMCID: PMC6671971 DOI: 10.1038/s41598-019-47606-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 07/19/2019] [Indexed: 11/08/2022] Open
Abstract
We present an efficient Schottky-diode detection scheme for Terahertz (THz) radiation, implemented on the material system epitaxial graphene on silicon carbide (SiC). It employs SiC as semiconductor and graphene as metal, with an epitaxially defined interface. For first prototypes, we report on broadband operation up to 580 GHz, limited only by the RC circuitry, with a responsivity of 1.1 A/W. Remarkably, the voltage dependence of the THz responsivity displays no deviations from DC responsivity, which encourages using this transparent device for exploring the high frequency limits of Schottky rectification in the optical regime. The performance of the detector is demonstrated by resolving sharp spectroscopic features of ethanol and acetone in a THz transmission experiment.
Collapse
|
6
|
Li L, Yang L, Wang X, Ni Y, Jiang J, Zhang G. Immobilizing copper-supported graphene with surface hydrogenation or hydroxylation: A first-principle study. Chem Phys 2019. [DOI: 10.1016/j.chemphys.2019.04.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
7
|
Ma D, Fu Z, Sui X, Bai K, Qiao J, Yan C, Zhang Y, Hu J, Xiao Q, Mao X, Duan W, He L. Modulating the Electronic Properties of Graphene by Self-Organized Sulfur Identical Nanoclusters and Atomic Superlattices Confined at an Interface. ACS NANO 2018; 12:10984-10991. [PMID: 30252446 DOI: 10.1021/acsnano.8b04874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Ordered atomic-scale superlattices on a surface hold great interest both for basic science and for potential applications in advanced technology. However, controlled fabrication of superlattices down to the atomic scale has proven exceptionally challenging. Here we develop a segregation method to realize self-organization of S superlattices at the interface of graphene and S-rich Cu substrates. Via scanning tunneling microscope measurements, we directly image well-ordered identical nanocluster superlattices and atomic superlattices under the cover of graphene. Scanning tunneling spectra show that the superlattices in turn could modulate the electronic structure of top-layer graphene. Importantly, a special-ordered S monatomic superlattice commensurate with a graphene lattice is found to drive semimetal graphene into a symmetry-broken phase-the electronic Kekulé distortion phase-which opens a bandgap of ∼245 meV.
Collapse
Affiliation(s)
- Donglin Ma
- Center for Advanced Quantum Studies, Department of Physics , Beijing Normal University , Beijing , 100875 , People's Republic of China
- Department of Physics , Capital Normal University , Beijing , 100048 , People's Republic of China
| | - Zhongqiu Fu
- Center for Advanced Quantum Studies, Department of Physics , Beijing Normal University , Beijing , 100875 , People's Republic of China
| | - Xuelei Sui
- State Key Laboratory of Low-Dimensional Quantum Physics and Collaborative Innovation Center of Quantum Matter, Department of Physics , Tsinghua University , Beijing , 100084 , People's Republic of China
| | - Keke Bai
- Center for Advanced Quantum Studies, Department of Physics , Beijing Normal University , Beijing , 100875 , People's Republic of China
| | - Jiabin Qiao
- Center for Advanced Quantum Studies, Department of Physics , Beijing Normal University , Beijing , 100875 , People's Republic of China
| | - Chao Yan
- Center for Advanced Quantum Studies, Department of Physics , Beijing Normal University , Beijing , 100875 , People's Republic of China
| | - Yu Zhang
- Center for Advanced Quantum Studies, Department of Physics , Beijing Normal University , Beijing , 100875 , People's Republic of China
| | - Jingyi Hu
- Center for Advanced Quantum Studies, Department of Physics , Beijing Normal University , Beijing , 100875 , People's Republic of China
| | - Qian Xiao
- Center for Advanced Quantum Studies, Department of Physics , Beijing Normal University , Beijing , 100875 , People's Republic of China
| | - Xinrui Mao
- Center for Advanced Quantum Studies, Department of Physics , Beijing Normal University , Beijing , 100875 , People's Republic of China
| | - Wenhui Duan
- State Key Laboratory of Low-Dimensional Quantum Physics and Collaborative Innovation Center of Quantum Matter, Department of Physics , Tsinghua University , Beijing , 100084 , People's Republic of China
| | - Lin He
- Center for Advanced Quantum Studies, Department of Physics , Beijing Normal University , Beijing , 100875 , People's Republic of China
| |
Collapse
|
8
|
Liu X, Hersam MC. Interface Characterization and Control of 2D Materials and Heterostructures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1801586. [PMID: 30039558 DOI: 10.1002/adma.201801586] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2018] [Revised: 04/09/2018] [Indexed: 05/28/2023]
Abstract
2D materials and heterostructures have attracted significant attention for a variety of nanoelectronic and optoelectronic applications. At the atomically thin limit, the material characteristics and functionalities are dominated by surface chemistry and interface coupling. Therefore, methods for comprehensively characterizing and precisely controlling surfaces and interfaces are required to realize the full technological potential of 2D materials. Here, the surface and interface properties that govern the performance of 2D materials are introduced. Then the experimental approaches that resolve surface and interface phenomena down to the atomic scale, as well as strategies that allow tuning and optimization of interfacial interactions in van der Waals heterostructures, are systematically reviewed. Finally, a future outlook that delineates the remaining challenges and opportunities for 2D material interface characterization and control is presented.
Collapse
Affiliation(s)
- Xiaolong Liu
- Applied Physics Graduate Program, Northwestern University, 2220 Campus Drive, Evanston, IL, 60208-3108, USA
| | - Mark C Hersam
- Applied Physics Graduate Program, Northwestern University, 2220 Campus Drive, Evanston, IL, 60208-3108, USA
- Department of Materials Science and Engineering, Department of Chemistry, Department of Medicine, Department of Electrical Engineering and Computer Science, Northwestern University, 2220 Campus Drive, Evanston, IL, 60208-3108, USA
| |
Collapse
|
9
|
Amjadipour M, Tadich A, Boeckl JJ, Lipton-Duffin J, MacLeod J, Iacopi F, Motta N. Quasi free-standing epitaxial graphene fabrication on 3C-SiC/Si(111). NANOTECHNOLOGY 2018; 29:145601. [PMID: 29376834 DOI: 10.1088/1361-6528/aaab1a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Growing graphene on SiC thin films on Si is a cheaper alternative to the growth on bulk SiC, and for this reason it has been recently intensively investigated. Here we study the effect of hydrogen intercalation on epitaxial graphene obtained by high temperature annealing on 3C-SiC/Si(111) in ultra-high vacuum. By using a combination of core-level photoelectron spectroscopy, low energy electron diffraction, and near-edge x-ray absorption fine structure (NEXAFS) we find that hydrogen saturates the Si atoms at the topmost layer of the substrate, leading to free-standing graphene on 3C-SiC/Si(111). The intercalated hydrogen fully desorbs after heating the sample at 850 °C and the buffer layer appears again, similar to what has been reported for bulk SiC. However, the NEXAFS analysis sheds new light on the effect of hydrogen intercalation, showing an improvement of graphene's flatness after annealing in atomic H at 600 °C. These results provide new insight into free-standing graphene fabrication on SiC/Si thin films.
Collapse
Affiliation(s)
- Mojtaba Amjadipour
- School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, QLD, Australia
| | | | | | | | | | | | | |
Collapse
|
10
|
Romero-Muñiz C, Martín-Recio A, Pou P, Gómez-Rodríguez JM, Pérez R. Unveiling the atomistic mechanisms for oxygen intercalation in a strongly interacting graphene–metal interface. Phys Chem Chem Phys 2018; 20:13370-13378. [PMID: 29721570 DOI: 10.1039/c8cp01032c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The atomistic mechanisms involved in the oxygen intercalation in the strongly interacting G/Rh(111) system are characterized in a comprehensive experimental and theoretical study, combining scanning tunneling microscopy and DFT calculations.
Collapse
Affiliation(s)
- Carlos Romero-Muñiz
- Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid
- E-28049 Madrid
- Spain
| | - Ana Martín-Recio
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid
- E-28049 Madrid
- Spain
| | - Pablo Pou
- Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid
- E-28049 Madrid
- Spain
- Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid
- E-28049 Madrid
| | - José M. Gómez-Rodríguez
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid
- E-28049 Madrid
- Spain
- Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid
- E-28049 Madrid
| | - Rubén Pérez
- Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid
- E-28049 Madrid
- Spain
- Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid
- E-28049 Madrid
| |
Collapse
|
11
|
Du C, Yu L, Liu X, Liu L, Wang CZ. Oscillatory electrostatic potential on graphene induced by group IV element decoration. Sci Rep 2017; 7:13152. [PMID: 29030602 PMCID: PMC5640640 DOI: 10.1038/s41598-017-13603-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Accepted: 09/26/2017] [Indexed: 11/25/2022] Open
Abstract
The structures and electronic properties of partial C, Si and Ge decorated graphene were investigated by first-principles calculations. The calculations show that the interaction between graphene and the decoration patches is weak and the semiconductor patches act as agents for weak electron doping without much disturbing graphene electronic π-bands. Redistribution of electrons due to the partial decoration causes the electrostatic potential lower in the decorated graphene areas, thus induced an electric field across the boundary between the decorated and non-decorated domains. Such an alternating electric field can change normal stochastic adatom diffusion to biased diffusion, leading to selective mass transport.
Collapse
Affiliation(s)
- Chunyan Du
- Center for Quantum Sciences and School of Physics, Northeast Normal University, Changchun, 130117, China
| | - Liwei Yu
- Center for Quantum Sciences and School of Physics, Northeast Normal University, Changchun, 130117, China
| | - Xiaojie Liu
- Center for Quantum Sciences and School of Physics, Northeast Normal University, Changchun, 130117, China.
| | - Lili Liu
- Department of Chemistry, School of Science, Beijing Technology and Business University, Beijing, 10084, China
| | - Cai-Zhuang Wang
- Ames Laboratory - US Department of Energy, and Department of Physics and Astronomy, Iowa State University, Ames, IA, 50011, USA
| |
Collapse
|
12
|
Kinder EW, Fuller A, Lin YC, Robinson JA, Fullerton-Shirey SK. Increasing the Room-Temperature Electric Double Layer Retention Time in Two-Dimensional Crystal FETs. ACS APPLIED MATERIALS & INTERFACES 2017; 9:25006-25013. [PMID: 28715196 DOI: 10.1021/acsami.7b03776] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Poly(vinyl alcohol) (PVA) and LiClO4, a solid polymer electrolyte with a glass transition temperature (Tg) of 80 °C, is used to electrostatically gate graphene field-effect transistors. The ions in PVA:LiClO4 are drifted into place by field-effect at T > Tg, providing n- or p-type doping, and when the device is cooled to room temperature, the polymer mobility and, hence ion mobility are arrested and the electric double layer (EDL) is "locked" into place in the absence of a gate bias. Unlike other electrolytes used to gate two-dimensional devices for which the Tg, and therefore the "locking" temperature, is well below room temperature, the electrolyte demonstrated in this work provides a route to achieve room-temperature EDL stability. Specifically, a 6 orders of magnitude increase in the room temperature EDL retention time is demonstrated over the commonly used electrolyte, poly(ethylene oxide) (PEO) and LiClO4. Hall measurements confirm that large sheet carrier densities can be achieved with PVA:LiClO4 at top gate programming voltages of ±2 V (-6.3 ± 0.03 × 1013 cm-2 for electrons and 1.6 ± 0.3 × 1014 cm-2 for holes). Transient drain current measurements show that at least 75% of the EDL is retained after more than 4 h at room temperature. Unlike PEO-based electrolytes, PVA:LiClO4 is compatible with the chemicals used in standard photolithographic processes enabling the direct deposition of patterned, metal contacts on the surface of the electrolyte. A thermal instability in the electrolyte is detected by both I-V measurements and differential scanning calorimetry, and FTIR measurements suggest that thermally catalyzed cross-linking may be driving phase separation between the polymer and the salt. Nevertheless, this work highlights how the relationship between polymer and ion mobility can be exploited to tune the state retention time and the charge carrier density of a 2D crystal transistor.
Collapse
Affiliation(s)
- Erich W Kinder
- Department of Electrical Engineering, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Ashley Fuller
- Department of Electrical Engineering, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Yu-Chuan Lin
- Department of Materials Science and Engineering, The Pennsylvania State University , University Park, Pennsylvania 16802, United States
- Center for 2-Dimensional and Layered Materials , 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
- Center for 2-Dimensional and Layered Materials , The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Susan K Fullerton-Shirey
- Department of Electrical Engineering, University of Notre Dame , Notre Dame, Indiana 46556, United States
| |
Collapse
|
13
|
Melios C, Winters M, Strupiński W, Panchal V, Giusca CE, Imalka Jayawardena KDG, Rorsman N, Silva SRP, Kazakova O. Tuning epitaxial graphene sensitivity to water by hydrogen intercalation. NANOSCALE 2017; 9:3440-3448. [PMID: 28232984 DOI: 10.1039/c6nr09465a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The effects of humidity on the electronic properties of quasi-free standing one layer graphene (QFS 1LG) are investigated via simultaneous magneto-transport in the van der Pauw geometry and local work function measurements in a controlled environment. QFS 1LG on 4H-SiC(0001) is obtained by hydrogen intercalation of the interfacial layer. In this system, the carrier concentration experiences a two-fold increase in sensitivity to changes in relative humidity as compared to the as-grown epitaxial graphene. This enhanced sensitivity to water is attributed to the lowering of the hydrophobicity of QFS 1LG, which results from spontaneous polarization of 4H-SiC(0001) strongly influencing the graphene. Moreover, the superior carrier mobility of the QFS 1LG system is retained even at the highest humidity. The work function maps constructed from Kelvin probe force microscopy also revealed higher sensitivity to water for 1LG compared to 2LG in both QFS 1LG and as-grown systems. These results point to a new field of applications for QFS 1LG, i.e., as humidity sensors, and the corresponding need for metrology in calibration of graphene-based sensors and devices.
Collapse
Affiliation(s)
- C Melios
- National Physical Laboratory, Teddington, TW11 0LW, UK. and Advanced Technology Institute, University of Surrey, Guildford, GU2 7XH, UK
| | - M Winters
- Chalmers University of Technology, Dept. of Microtechnology and Nanoscience, Göteborg, 412-96, Sweden
| | - W Strupiński
- Institute of Electronic Materials Technology, Warsaw, 01-919, Poland
| | - V Panchal
- National Physical Laboratory, Teddington, TW11 0LW, UK.
| | - C E Giusca
- National Physical Laboratory, Teddington, TW11 0LW, UK.
| | | | - N Rorsman
- Chalmers University of Technology, Dept. of Microtechnology and Nanoscience, Göteborg, 412-96, Sweden
| | - S Ravi P Silva
- Advanced Technology Institute, University of Surrey, Guildford, GU2 7XH, UK
| | - O Kazakova
- National Physical Laboratory, Teddington, TW11 0LW, UK.
| |
Collapse
|
14
|
Pierucci D, Henck H, Ben Aziza Z, Naylor CH, Balan A, Rault JE, Silly MG, Dappe YJ, Bertran F, Le Fèvre P, Sirotti F, Johnson ATC, Ouerghi A. Tunable Doping in Hydrogenated Single Layered Molybdenum Disulfide. ACS NANO 2017; 11:1755-1761. [PMID: 28146631 DOI: 10.1021/acsnano.6b07661] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Structural defects in the molybdenum disulfide (MoS2) monolayer are widely known for strongly altering its properties. Therefore, a deep understanding of these structural defects and how they affect MoS2 electronic properties is of fundamental importance. Here, we report on the incorporation of atomic hydrogen in monolayered MoS2 to tune its structural defects. We demonstrate that the electronic properties of single layer MoS2 can be tuned from the intrinsic electron (n) to hole (p) doping via controlled exposure to atomic hydrogen at room temperature. Moreover, this hydrogenation process represents a viable technique to completely saturate the sulfur vacancies present in the MoS2 flakes. The successful incorporation of hydrogen in MoS2 leads to the modification of the electronic properties as evidenced by high resolution X-ray photoemission spectroscopy and density functional theory calculations. Micro-Raman spectroscopy and angle resolved photoemission spectroscopy measurements show the high quality of the hydrogenated MoS2 confirming the efficiency of our hydrogenation process. These results demonstrate that the MoS2 hydrogenation could be a significant and efficient way to achieve tunable doping of transition metal dichalcogenides (TMD) materials with non-TMD elements.
Collapse
Affiliation(s)
- Debora Pierucci
- Centre de Nanosciences et de Nanotechnologies, CNRS, Univ. Paris-Sud, Université Paris-Saclay , C2N - Marcoussis, F91460 Marcoussis, France
| | - Hugo Henck
- Centre de Nanosciences et de Nanotechnologies, CNRS, Univ. Paris-Sud, Université Paris-Saclay , C2N - Marcoussis, F91460 Marcoussis, France
| | - Zeineb Ben Aziza
- Centre de Nanosciences et de Nanotechnologies, CNRS, Univ. Paris-Sud, Université Paris-Saclay , C2N - Marcoussis, F91460 Marcoussis, France
| | - Carl H Naylor
- Department of Physics and Astronomy, University of Pennsylvania , 209S 33rd Street, Philadelphia, Pennsylvania 19104, United States
| | - Adrian Balan
- Department of Physics and Astronomy, University of Pennsylvania , 209S 33rd Street, Philadelphia, Pennsylvania 19104, United States
| | - Julien E Rault
- Synchrotron-SOLEIL , Saint-Aubin, BP48, F91192 Gif sur Yvette Cedex, France
| | - Mathieu G Silly
- Synchrotron-SOLEIL , Saint-Aubin, BP48, F91192 Gif sur Yvette Cedex, France
| | - Yannick J Dappe
- SPEC, CEA, CNRS, Université Paris-Saclay , CEA Saclay, F91191 Gif-sur-Yvette Cedex, France
| | - François Bertran
- Synchrotron-SOLEIL , Saint-Aubin, BP48, F91192 Gif sur Yvette Cedex, France
| | - Patrick Le Fèvre
- Synchrotron-SOLEIL , Saint-Aubin, BP48, F91192 Gif sur Yvette Cedex, France
| | - Fausto Sirotti
- Synchrotron-SOLEIL , Saint-Aubin, BP48, F91192 Gif sur Yvette Cedex, France
| | - A T Charlie Johnson
- Department of Physics and Astronomy, University of Pennsylvania , 209S 33rd Street, Philadelphia, Pennsylvania 19104, United States
| | - Abdelkarim Ouerghi
- Centre de Nanosciences et de Nanotechnologies, CNRS, Univ. Paris-Sud, Université Paris-Saclay , C2N - Marcoussis, F91460 Marcoussis, France
| |
Collapse
|
15
|
Iwasaki T, Muruganathan M, Schmidt ME, Mizuta H. Partial hydrogenation induced interaction in a graphene-SiO 2 interface: irreversible modulation of device characteristics. NANOSCALE 2017; 9:1662-1669. [PMID: 28074959 DOI: 10.1039/c6nr08117g] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The transformation of systematic vacuum and hydrogen annealing effects in graphene devices on the SiO2 surface is reported based on experimental and van der Waals interaction corrected density functional theory (DFT) simulation results. Vacuum annealing removes p-type dopants and reduces charged impurity scattering in graphene. Moreover, it induces n-type doping into graphene, leading to the improvement of the electron mobility and conductivity in the electron transport regime, which are reversed by exposing to atmospheric environment. On the other hand, annealing in hydrogen/argon gas results in smaller n-type doping along with a decrease in the overall conductivity and carrier mobility. This degradation of the conductivity is irreversible even the graphene devices are exposed to ambience. This was clarified by DFT simulations: initially, silicon dangling bonds were partially terminated by hydrogen, subsequently, the remaining dangling bonds became active and the distance between the graphene and SiO2 surface decreased. Moreover, both annealing methods affect the graphene channel including the vicinity of the metal contacts, which plays an important role in asymmetric carrier transport.
Collapse
Affiliation(s)
- Takuya Iwasaki
- School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292, Japan.
| | - Manoharan Muruganathan
- School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292, Japan.
| | - Marek E Schmidt
- School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292, Japan.
| | - Hiroshi Mizuta
- School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292, Japan. and Nanoelectronics and Nanotechnology Research Group, University of Southampton, Highfield, Southampton SO17 1BJ, UK and Institute of Microengineering and Nanoelectronics (IMEN), The National University of Malaysia, 43600 Bangi, Selangor, Malaysia
| |
Collapse
|
16
|
Fu Q, Bao X. Surface chemistry and catalysis confined under two-dimensional materials. Chem Soc Rev 2017; 46:1842-1874. [DOI: 10.1039/c6cs00424e] [Citation(s) in RCA: 292] [Impact Index Per Article: 41.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Interfaces between 2D material overlayers and solid surfaces provide confined spaces for chemical processes, which have stimulated new chemistry under a 2D cover.
Collapse
Affiliation(s)
- Qiang Fu
- State Key Laboratory of Catalysis
- iChEM
- Dalian Institute of Chemical Physics, the Chinese Academy of Sciences
- Dalian 116023
- P. R. China
| | - Xinhe Bao
- State Key Laboratory of Catalysis
- iChEM
- Dalian Institute of Chemical Physics, the Chinese Academy of Sciences
- Dalian 116023
- P. R. China
| |
Collapse
|
17
|
Lin YC, Li J, de la Barrera SC, Eichfeld SM, Nie Y, Addou R, Mende PC, Wallace RM, Cho K, Feenstra RM, Robinson JA. Tuning electronic transport in epitaxial graphene-based van der Waals heterostructures. NANOSCALE 2016; 8:8947-8954. [PMID: 27073972 DOI: 10.1039/c6nr01902a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Two-dimensional tungsten diselenide (WSe2) has been used as a component in atomically thin photovoltaic devices, field effect transistors, and tunneling diodes in tandem with graphene. In some applications it is necessary to achieve efficient charge transport across the interface of layered WSe2-graphene, a semiconductor to semimetal junction with a van der Waals (vdW) gap. In such cases, band alignment engineering is required to ensure a low-resistance, ohmic contact. In this work, we investigate the impact of graphene electronic properties on the transport at the WSe2-graphene interface. Electrical transport measurements reveal a lower resistance between WSe2 and fully hydrogenated epitaxial graphene (EG(FH)) compared to WSe2 grown on partially hydrogenated epitaxial graphene (EGPH). Using low-energy electron microscopy and reflectivity on these samples, we extract the work function difference between the WSe2 and graphene and employ a charge transfer model to determine the WSe2 carrier density in both cases. The results indicate that WSe2-EG(FH) displays ohmic behavior at small biases due to a large hole density in the WSe2, whereas WSe2-EG(PH) forms a Schottky barrier junction.
Collapse
Affiliation(s)
- Yu-Chuan Lin
- Department of Materials Science and Engineering and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, PA 16802, USA.
| | - Jun Li
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | | | - Sarah M Eichfeld
- Department of Materials Science and Engineering and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, PA 16802, USA.
| | - Yifan Nie
- Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas 75080, USA
| | - Rafik Addou
- Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas 75080, USA
| | - Patrick C Mende
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Robert M Wallace
- Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas 75080, USA
| | - Kyeongjae Cho
- Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas 75080, USA
| | - Randall M Feenstra
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Joshua A Robinson
- Department of Materials Science and Engineering and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, PA 16802, USA.
| |
Collapse
|
18
|
Morrow WK, Pearton SJ, Ren F. Review of Graphene as a Solid State Diffusion Barrier. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2016; 12:120-134. [PMID: 26523843 DOI: 10.1002/smll.201501120] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Revised: 05/29/2015] [Indexed: 06/05/2023]
Abstract
Conventional thin-film diffusion barriers consist of 3D bulk films with high chemical and thermal stability. The purpose of the barrier material is to prevent intermixing or penetration from the two materials that encase it. Adhesion to both top and bottom materials is critical to the success of the barrier. Here, the effectiveness of a single atomic layer of graphene as a solid-state diffusion barrier for common metal schemes used in microelectronics is reviewed, and specific examples are discussed. Initial studies of electrical contacts to graphene show a distinct separation in behavior between metallic groups that strongly or weakly bond to it. The two basic classes of metal reactions with graphene are either physisorbed metals, which bond weakly with graphene, or chemisorbed metals, which bond strongly to graphene. For graphene diffusion barrier testing on Si substrates, an effective barrier can be achieved through the formation of a carbide layer with metals that are chemisorbed. For physisorbed metals, the barrier failure mechanism is loss of adhesion at the metal–graphene interface. A graphene layer encased between two metal layers, in certain cases, can increase the binding energy of both films with graphene, however, certain combinations of metal films are detrimental to the bonding with graphene. While the prospects for graphene's future as a solid-state diffusion barrier are positive, there are open questions, and areas for future research are discussed. A better understanding of the mechanisms which influence graphene's ability to be an effective diffusion barrier in microelectronic applications is required, and additional experiments are needed on a broader range of metals, as well as common metal stack contact structures used in microelectronic applications. The role of defects in the graphene is also a key area, since they will probably influence the barrier properties.
Collapse
Affiliation(s)
- Wayne K Morrow
- Department of Materials Science and Engineering, University of Florida, Gainesville, FL, 32606, USA
| | - Stephen J Pearton
- Department of Materials Science and Engineering, University of Florida, Gainesville, FL, 32606, USA
| | - Fan Ren
- Department of Chemical Engineering, University of Florida, Gainesville, FL, 32606, USA
| |
Collapse
|
19
|
Gao P, Yang Y, Bao D, Chen Y, Wang Y, Yang P, Zhang X. Flattening sol–gel nanospheres into a carbon sheet-intercalated cobalt/carbon/cobalt sandwich-nanostructure. Inorg Chem Front 2016. [DOI: 10.1039/c5qi00215j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Uniform cobalt/carbon/cobalt sandwich-like nanosheet stacks have been constructed by using sol–gel nanospheres covered with CoII–CoIII–LDH as a precursor.
Collapse
Affiliation(s)
- Peng Gao
- Key Laboratory of Superlight Materials and Surface Technology
- Ministry of Education
- College of Materials Science and Chemical Engineering
- Harbin Engineering University
- Harbin
| | - Yurong Yang
- Key Laboratory of Superlight Materials and Surface Technology
- Ministry of Education
- College of Materials Science and Chemical Engineering
- Harbin Engineering University
- Harbin
| | - Di Bao
- Key Laboratory of Superlight Materials and Surface Technology
- Ministry of Education
- College of Materials Science and Chemical Engineering
- Harbin Engineering University
- Harbin
| | - Yujin Chen
- College of Science
- Harbin Engineering University
- Harbin
- P. R. China
| | - Ying Wang
- Key Laboratory of Superlight Materials and Surface Technology
- Ministry of Education
- College of Materials Science and Chemical Engineering
- Harbin Engineering University
- Harbin
| | - Piaoping Yang
- Key Laboratory of Superlight Materials and Surface Technology
- Ministry of Education
- College of Materials Science and Chemical Engineering
- Harbin Engineering University
- Harbin
| | - Xitian Zhang
- Key Laboratory for Photonic and Electric Bandgap Materials
- Ministry of Education
- Harbin Normal University
- Harbin
- P. R. China
| |
Collapse
|
20
|
Li X, Sun S, Zhang J, Luo K, Gao P, Wu T, Du S, Wang Y, Zhou X, Sha L, Yang Y, Yang P, Wang Y, Chen Y. Hybridization of inorganic CoB noncrystal with graphene and its Kubas-enhanced hydrogen adsorption at room temperature. RSC Adv 2016. [DOI: 10.1039/c6ra19238f] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In this work an archetypical hybrid material has been prepared by the reaction of an inorganic CoB noncrystal with graphene by a high-energy ball-milling process, which showed an enhanced electrochemical hydrogen storage ability induced by the Co–B–C structure.
Collapse
|
21
|
Atomically thin resonant tunnel diodes built from synthetic van der Waals heterostructures. Nat Commun 2015; 6:7311. [PMID: 26088295 PMCID: PMC4557306 DOI: 10.1038/ncomms8311] [Citation(s) in RCA: 150] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 04/27/2015] [Indexed: 12/24/2022] Open
Abstract
Vertical integration of two-dimensional van der Waals materials is predicted to lead to novel electronic and optical properties not found in the constituent layers. Here, we present the direct synthesis of two unique, atomically thin, multi-junction heterostructures by combining graphene with the monolayer transition-metal dichalcogenides: molybdenum disulfide (MoS2), molybdenum diselenide (MoSe2) and tungsten diselenide (WSe2). The realization of MoS2–WSe2–graphene and WSe2–MoS2–graphene heterostructures leads to resonant tunnelling in an atomically thin stack with spectrally narrow, room temperature negative differential resistance characteristics. The family of two-dimensional materials is ever growing, but greater functionality can be realized by combining them together. Here, the authors report the direct synthesis of multijunction heterostructures made from graphene, tungsten diselenide and either molybdenum disulphide or molybdenum diselenide.
Collapse
|
22
|
Schwierz F, Pezoldt J, Granzner R. Two-dimensional materials and their prospects in transistor electronics. NANOSCALE 2015; 7:8261-8283. [PMID: 25898786 DOI: 10.1039/c5nr01052g] [Citation(s) in RCA: 176] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
During the past decade, two-dimensional materials have attracted incredible interest from the electronic device community. The first two-dimensional material studied in detail was graphene and, since 2007, it has intensively been explored as a material for electronic devices, in particular, transistors. While graphene transistors are still on the agenda, researchers have extended their work to two-dimensional materials beyond graphene and the number of two-dimensional materials under examination has literally exploded recently. Meanwhile several hundreds of different two-dimensional materials are known, a substantial part of them is considered useful for transistors, and experimental transistors with channels of different two-dimensional materials have been demonstrated. In spite of the rapid progress in the field, the prospects of two-dimensional transistors still remain vague and optimistic opinions face rather reserved assessments. The intention of the present paper is to shed more light on the merits and drawbacks of two-dimensional materials for transistor electronics and to add a few more facets to the ongoing discussion on the prospects of two-dimensional transistors. To this end, we compose a wish list of properties for a good transistor channel material and examine to what extent the two-dimensional materials fulfill the criteria of the list. The state-of-the-art two-dimensional transistors are reviewed and a balanced view of both the pros and cons of these devices is provided.
Collapse
Affiliation(s)
- F Schwierz
- Institut für Mikro- und Nanoelektronik, Technische Universität Ilmenau, PF 100565, 98684 Ilmenau, Germany.
| | | | | |
Collapse
|
23
|
Sorger C, Hertel S, Jobst J, Steiner C, Meil K, Ullmann K, Albert A, Wang Y, Krieger M, Ristein J, Maier S, Weber HB. Gateless patterning of epitaxial graphene by local intercalation. NANOTECHNOLOGY 2015; 26:025302. [PMID: 25517943 DOI: 10.1088/0957-4484/26/2/025302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We present a technique to pattern the charge density of a large-area epitaxial graphene sheet locally without using metallic gates. Instead, local intercalation of the graphene-substrate interface can selectively be established in the vicinity of graphene edges or predefined voids. It provides changes of the work function of several hundred meV, corresponding to a conversion from n-type to p-type charge carriers. This assignment is supported by photoelectron spectroscopy, scanning tunneling microscopy, scanning electron microscopy and Hall effect measurements. The technique introduces materials contrast to a graphene sheet in a variety of geometries and thus allows for novel experiments and novel functionalities.
Collapse
Affiliation(s)
- C Sorger
- Lehrstuhl für Angewandte Physik, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstr. 7, D-91058 Erlangen, Germany
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
24
|
Norimatsu W, Kusunoki M. Epitaxial graphene on SiC{0001}: advances and perspectives. Phys Chem Chem Phys 2014; 16:3501-11. [PMID: 24434866 DOI: 10.1039/c3cp54523g] [Citation(s) in RCA: 125] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
We review here recent progress on epitaxial graphene grown on a SiC substrate. Epitaxial graphene can be easily grown by heating the SiC single crystal in a high vacuum or in an inert gas atmosphere. The SiC surfaces used for graphene growth contain Si- and C-terminated faces. On the Si-face, homogeneous and clean graphene can be grown with a controlled number of layers, and the carrier mobility reaches as high as several m(2) V s(-1), although this is reduced by the presence of the substrate steps. On the C-face, although the number of layers is not homogeneous, twisted bilayer graphene can be grown, which is expected to be the technique of choice to modify the electronic structure of graphene. From the application point of view, graphene on SiC will be the platform used to fabricate high-speed electronic devices and dense graphene nanoribbon arrays, which will be used to introduce a bandgap.
Collapse
Affiliation(s)
- Wataru Norimatsu
- Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya-shi, Aichi-ken 464-8603, Japan.
| | | |
Collapse
|
25
|
Liu FH, Lo ST, Chuang C, Woo TP, Lee HY, Liu CW, Liu CI, Huang LI, Liu CH, Yang Y, Chang CYS, Li LJ, Mende PC, Feenstra RM, Elmquist RE, Liang CT. Hot carriers in epitaxial graphene sheets with and without hydrogen intercalation: role of substrate coupling. NANOSCALE 2014; 6:10562-10568. [PMID: 25117572 DOI: 10.1039/c4nr02980a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The development of graphene electronic devices produced by industry relies on efficient control of heat transfer from the graphene sheet to its environment. In nanoscale devices, heat is one of the major obstacles to the operation of such devices at high frequencies. Here we have studied the transport of hot carriers in epitaxial graphene sheets on 6H-SiC (0001) substrates with and without hydrogen intercalation by driving the device into the non-equilibrium regime. Interestingly, we have demonstrated that the energy relaxation time of the device without hydrogen intercalation is two orders of magnitude shorter than that with hydrogen intercalation, suggesting application of epitaxial graphene in high-frequency devices which require outstanding heat exchange with an outside cooling source.
Collapse
Affiliation(s)
- Fan-Hung Liu
- Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
26
|
Lin YC, Lu N, Perea-Lopez N, Li J, Lin Z, Peng X, Lee CH, Sun C, Calderin L, Browning PN, Bresnehan MS, Kim MJ, Mayer TS, Terrones M, Robinson JA. Direct synthesis of van der Waals solids. ACS NANO 2014; 8:3715-3723. [PMID: 24641706 DOI: 10.1021/nn5003858] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The stacking of two-dimensional layered materials, such as semiconducting transition metal dichalcogenides (TMDs), insulating hexagonal boron nitride (hBN), and semimetallic graphene, has been theorized to produce tunable electronic and optoelectronic properties. Here we demonstrate the direct growth of MoS2, WSe2, and hBN on epitaxial graphene to form large-area van der Waals heterostructures. We reveal that the properties of the underlying graphene dictate properties of the heterostructures, where strain, wrinkling, and defects on the surface of graphene act as nucleation centers for lateral growth of the overlayer. Additionally, we show that the direct synthesis of TMDs on epitaxial graphene exhibits atomically sharp interfaces. Finally, we demonstrate that direct growth of MoS2 on epitaxial graphene can lead to a 10(3) improvement in photoresponse compared to MoS2 alone.
Collapse
Affiliation(s)
- Yu-Chuan Lin
- Department of Materials Science and Engineering and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University , University Park, Pennsylvania 16802, United States
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
27
|
High Electron Mobility in Epitaxial Graphene on 4H-SiC(0001) via post-growth annealing under hydrogen. Sci Rep 2014; 4:4558. [PMID: 24691055 PMCID: PMC3972502 DOI: 10.1038/srep04558] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Accepted: 03/17/2014] [Indexed: 01/30/2023] Open
Abstract
We investigate the magneto-transport properties of epitaxial graphene single-layer on 4H-SiC(0001), grown by atmospheric pressure graphitization in Ar, followed by H2 intercalation. We directly demonstrate the importance of saturating the Si dangling bonds at the graphene/SiC(0001) interface to achieve high carrier mobility. Upon successful Si dangling bonds elimination, carrier mobility increases from 3 000 cm2V−1s−1 to >11 000 cm2V−1s−1 at 0.3 K. Additionally, graphene electron concentration tends to decrease from a few 1012 cm−2 to less than 1012 cm−2. For a typical large (30 × 280 μm2) Hall bar, we report the observation of the integer quantum Hall states at 0.3 K with well developed transversal resistance plateaus at Landau level filling factors of ν = 2, 6, 10, 14… 42 and Shubnikov de Haas oscillation of the longitudinal resistivity observed from about 1 T. In such a device, the Hall state quantization at ν = 2, at 19 T and 0.3 K, can be very robust: the dissipation in electronic transport can stay very low, with the longitudinal resistivity lower than 5 mΩ, for measurement currents as high as 250 μA. This is very promising in the view of an application in metrology.
Collapse
|
28
|
Emery JD, Detlefs B, Karmel HJ, Nyakiti LO, Gaskill DK, Hersam MC, Zegenhagen J, Bedzyk MJ. Chemically resolved interface structure of epitaxial graphene on SiC(0001). PHYSICAL REVIEW LETTERS 2013; 111:215501. [PMID: 24313501 DOI: 10.1103/physrevlett.111.215501] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Indexed: 06/02/2023]
Abstract
Atomic-layer 2D crystals have unique properties that can be significantly modified through interaction with an underlying support. For epitaxial graphene on SiC(0001), the interface strongly influences the electronic properties of the overlaying graphene. We demonstrate a novel combination of x-ray scattering and spectroscopy for studying the complexities of such a buried interface structure. This approach employs x-ray standing wave-excited photoelectron spectroscopy in conjunction with x-ray reflectivity to produce a highly resolved chemically sensitive atomic profile for the terminal substrate bilayers, interface, and graphene layers along the SiC[0001] direction.
Collapse
Affiliation(s)
- Jonathan D Emery
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
| | | | | | | | | | | | | | | |
Collapse
|
29
|
Schumacher S, Wehling TO, Lazić P, Runte S, Förster DF, Busse C, Petrović M, Kralj M, Blügel S, Atodiresei N, Caciuc V, Michely T. The backside of graphene: manipulating adsorption by intercalation. NANO LETTERS 2013; 13:5013-5019. [PMID: 24131290 DOI: 10.1021/nl402797j] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The ease by which graphene is affected through contact with other materials is one of its unique features and defines an integral part of its potential for applications. Here, it will be demonstrated that intercalation, the insertion of atomic layers in between the backside of graphene and the supporting substrate, is an efficient tool to change its interaction with the environment on the frontside. By partial intercalation of graphene on Ir(111) with Eu or Cs we induce strongly n-doped graphene patches through the contact with these intercalants. They coexist with nonintercalated, slightly p-doped graphene patches. We employ these backside doping patterns to directly visualize doping induced binding energy differences of ionic adsorbates to graphene through low-temperature scanning tunneling microscopy. Density functional theory confirms these binding energy differences and shows that they are related to the graphene doping level.
Collapse
Affiliation(s)
- Stefan Schumacher
- II. Physikalisches Institut , Universität zu Köln , Zülpicher Straße 77, 50937 Köln, Germany
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
30
|
Chen J, Nesterov ML, Nikitin AY, Thongrattanasiri S, Alonso-González P, Slipchenko TM, Speck F, Ostler M, Seyller T, Crassee I, Koppens FHL, Martin-Moreno L, García de Abajo FJ, Kuzmenko AB, Hillenbrand R. Strong plasmon reflection at nanometer-size gaps in monolayer graphene on SiC. NANO LETTERS 2013; 13:6210-6215. [PMID: 24188400 DOI: 10.1021/nl403622t] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We employ tip-enhanced infrared near-field microscopy to study the plasmonic properties of epitaxial quasi-free-standing monolayer graphene on silicon carbide. The near-field images reveal propagating graphene plasmons, as well as a strong plasmon reflection at gaps in the graphene layer, which appear at the steps between the SiC terraces. When the step height is around 1.5 nm, which is two orders of magnitude smaller than the plasmon wavelength, the reflection signal reaches 20% of its value at graphene edges, and it approaches 50% for step heights as small as 5 nm. This intriguing observation is corroborated by numerical simulations and explained by the accumulation of a line charge at the graphene termination. The associated electromagnetic fields at the graphene termination decay within a few nanometers, thus preventing efficient plasmon transmission across nanoscale gaps. Our work suggests that plasmon propagation in graphene-based circuits can be tailored using extremely compact nanostructures, such as ultranarrow gaps. It also demonstrates that tip-enhanced near-field microscopy is a powerful contactless tool to examine nanoscale defects in graphene.
Collapse
Affiliation(s)
- Jianing Chen
- CIC nanoGUNE Consolider, 20018 Donostia-San Sebastián, Spain
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
31
|
Hernández SC, Bennett CJC, Junkermeier CE, Tsoi SD, Bezares FJ, Stine R, Robinson JT, Lock EH, Boris DR, Pate BD, Caldwell JD, Reinecke TL, Sheehan PE, Walton SG. Chemical gradients on graphene to drive droplet motion. ACS NANO 2013; 7:4746-4755. [PMID: 23659463 DOI: 10.1021/nn304267b] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
This work demonstrates the production of a well-controlled, chemical gradient on the surface of graphene. By inducing a gradient of oxygen functional groups, drops of water and dimethyl-methylphosphonate (a nerve agent simulant) are "pulled" in the direction of increasing oxygen content, while fluorine gradients "push" the droplet motion in the direction of decreasing fluorine content. The direction of motion is broadly attributed to increasing/decreasing hydrophilicity, which is correlated to high/low adhesion and binding energy. Such tunability in surface chemistry provides additional capabilities in device design for applications ranging from microfluidics to chemical sensing.
Collapse
Affiliation(s)
- Sandra C Hernández
- NRC Postdoctoral Research Associateship Program, Naval Research Laboratory, Washington, DC 20375, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
32
|
Guo Z, Dong R, Chakraborty PS, Lourenco N, Palmer J, Hu Y, Ruan M, Hankinson J, Kunc J, Cressler JD, Berger C, de Heer WA. Record maximum oscillation frequency in C-face epitaxial graphene transistors. NANO LETTERS 2013; 13:942-947. [PMID: 23418924 DOI: 10.1021/nl303587r] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The maximum oscillation frequency (fmax) quantifies the practical upper bound for useful circuit operation. We report here an fmax of 70 GHz in transistors using epitaxial graphene grown on the C-face of SiC. This is a significant improvement over Si-face epitaxial graphene used in the prior high-frequency transistor studies, exemplifying the superior electronics potential of C-face epitaxial graphene. Careful transistor design using a high κ dielectric T-gate and self-aligned contacts further contributed to the record-breaking fmax.
Collapse
Affiliation(s)
- Zelei Guo
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
33
|
Schumacher S, Förster DF, Rösner M, Wehling TO, Michely T. Strain in epitaxial graphene visualized by intercalation. PHYSICAL REVIEW LETTERS 2013; 110:086111. [PMID: 23473177 DOI: 10.1103/physrevlett.110.086111] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Indexed: 06/01/2023]
Abstract
Intercalation of Eu under graphene on Ir(111) results in patterns oriented along the graphene moiré and quantized in size by its unit mesh. The patterns are formed by stripes, compact islands, and channels. Over a wide range of intercalated amounts the step concentration of the pattern has a rather constant saturation value. These findings are explained by the chemically modulated binding of graphene to the substrate and the preexisting strain in graphene due to its cooldown from the growth temperature. Local variations in the intercalation step density appear to reflect local variations in the preexisting strain.
Collapse
Affiliation(s)
- Stefan Schumacher
- II Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany.
| | | | | | | | | |
Collapse
|
34
|
Deretzis I, La Magna A. Interaction between hydrogen flux and carbon monolayer on SiC(0001): graphene formation kinetics. NANOSCALE 2013; 5:671-680. [PMID: 23223677 DOI: 10.1039/c2nr33081d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Manipulation of graphene-based systems is a formidable challenge, since it requires the control of atomic interactions over long timescales. Although the effectiveness of a certain number of processes has been experimentally demonstrated, the underlying atomic mechanisms are often not understood. An import class of techniques relies on the interaction between hydrogen and graphene, which is the focus of this research. In particular, the growth of epitaxial graphene on SiC(0001) is subject to a single-atom-thick interface carbon layer strongly bound to the substrate, which can be detached through hydrogen intercalation. Here we report that a nucleation phenomenon induces the transformation of this buffer layer into graphene. We study the graphenization dynamics by an ab initio based method that permits the simulation of large systems with an atomic resolution, spanning the time scales from nanoseconds to hours. The early evolution stage (∼ms time scale) is characterised by the formation of a metastable H layer deposited on the C surface. H penetration in the interface between the C monolayer and the SiC(0001) surface is a rare event due to the large penetration barrier, which is ∼2 eV. However, at high H densities, energetically favoured Si-H bonding appears on the substrate's surface. The local increase of the H density at the interface due to statistical transitions leads to the graphenization of the overlying C atoms. Thermally activated density fluctuations promote the formation of these graphene-like islands on the buffer layer: this nucleation phenomenon is evidenced by our simulations at a later evolution stage (>10(2) s at 700 °C for ∼3.6 × 10(15) at. cm(-2) s(-1) H flux). Such nuclei grow and quasi-freestanding graphene forms if the exposition to the H flux continues for a sufficiently long time (∼30 min for the same conditions). We have systematically explored this phenomenon by varying the substrate temperature and the H flux, demonstrating that the surface morphology during graphenization and post-graphenization anneals significantly depends on these variables. The computational findings are consistent with the experimental analyses reported so far and could serve as guidelines for future experimental works on graphene manipulation.
Collapse
Affiliation(s)
- I Deretzis
- CNR-IMM, Strada VIII, 5, 95121, Catania, Italy
| | | |
Collapse
|
35
|
Grånäs E, Knudsen J, Schröder UA, Gerber T, Busse C, Arman MA, Schulte K, Andersen JN, Michely T. Oxygen intercalation under graphene on Ir(111): energetics, kinetics, and the role of graphene edges. ACS NANO 2012; 6:9951-9963. [PMID: 23039853 DOI: 10.1021/nn303548z] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Using X-ray photoemission spectroscopy (XPS) and scanning tunneling microscopy (STM) we resolve the temperature-, time-, and flake size-dependent intercalation phases of oxygen underneath graphene on Ir(111) formed upon exposure to molecular oxygen. Through the applied pressure of molecular oxygen the atomic oxygen created on the bare Ir terraces is driven underneath graphene flakes. The importance of substrate steps and of the unbinding of graphene flake edges from the substrate for the intercalation is identified. With the use of CO titration to selectively remove oxygen from the bare Ir terraces the energetics of intercalation is uncovered. Cluster decoration techniques are used as an efficient tool to visualize intercalation processes in real space.
Collapse
Affiliation(s)
- Elin Grånäs
- Division of Synchrotron Radiation Research, Lund University, Box 118, 221 00 Lund, Sweden
| | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Kim M, Hwang J, Lepak LA, Lee JW, Spencer MG, Tiwari S. Improvement of carrier mobility of top-gated SiC epitaxial graphene transistors using a PVA dielectric buffer layer. NANOTECHNOLOGY 2012; 23:335202. [PMID: 22842470 DOI: 10.1088/0957-4484/23/33/335202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The effects of treatment with polyvinyl alcohol (PVA) and a dielectric film of HfO(2) on the properties of SiC based epitaxial graphene have been explored and analyzed. We have characterized the carrier mobility of graphene on Si-face and C-face SiC with a layer of HfO(2), with or without an initial PVA treatment on the device active layer. Epitaxial graphene grown on the C-face displays a higher mobility than a film grown on the silicon face. Also, the mobility in the presence of the PVA treatment with HfO(2) dielectric layer has been improved, compared with the mobility after deposition of only gate dielectric: ∼20% in C-face graphene and ∼90% in Si-face graphene. This is a major improvement over the degradation normally observed with dielectric/graphene systems.
Collapse
Affiliation(s)
- Moonkyung Kim
- Department of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853, USA.
| | | | | | | | | | | |
Collapse
|
37
|
Man KL, Altman MS. Low energy electron microscopy and photoemission electron microscopy investigation of graphene. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:314209. [PMID: 22820702 DOI: 10.1088/0953-8984/24/31/314209] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Low energy electron microscopy (LEEM) and photoemission electron microscopy (PEEM) are two powerful techniques for the investigation of surfaces, thin films and surface supported nanostructures. In this review, we examine the contributions of these microscopy techniques to our understanding of graphene in recent years. These contributions have been made in studies of graphene on various metal and SiC surfaces and free-standing graphene. We discuss how the real-time imaging capability of LEEM facilitates a deeper understanding of the mechanisms of dynamic processes, such as growth and intercalation. Numerous examples also demonstrate how imaging and the various available complementary measurement capabilities, such as selected area or micro low energy electron diffraction (μLEED) and micro angle resolved photoelectron spectroscopy (μARPES), allow the investigation of local properties in spatially inhomogeneous graphene samples.
Collapse
Affiliation(s)
- K L Man
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
| | | |
Collapse
|
38
|
Kageshima H, Hibino H, Tanabe S. The physics of epitaxial graphene on SiC(0001). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:314215. [PMID: 22820985 DOI: 10.1088/0953-8984/24/31/314215] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Various physical properties of epitaxial graphene grown on SiC(0001) are studied. First, the electronic transport in epitaxial bilayer graphene on SiC(0001) and quasi-free-standing bilayer graphene on SiC(0001) is investigated. The dependences of the resistance and the polarity of the Hall resistance at zero gate voltage on the top-gate voltage show that the carrier types are electron and hole, respectively. The mobility evaluated at various carrier densities indicates that the quasi-free-standing bilayer graphene shows higher mobility than the epitaxial bilayer graphene when they are compared at the same carrier density. The difference in mobility is thought to come from the domain size of the graphene sheet formed. To clarify a guiding principle for controlling graphene quality, the mechanism of epitaxial graphene growth is also studied theoretically. It is found that a new graphene sheet grows from the interface between the old graphene sheets and the SiC substrate. Further studies on the energetics reveal the importance of the role of the step on the SiC surface. A first-principles calculation unequivocally shows that the C prefers to release from the step edge and to aggregate as graphene nuclei along the step edge rather than be left on the terrace. It is also shown that the edges of the existing graphene more preferentially absorb the isolated C atoms. For some annealing conditions, experiments can also provide graphene islands on SiC(0001) surfaces. The atomic structures are studied theoretically together with their growth mechanism. The proposed embedded island structures actually act as a graphene island electronically, and those with zigzag edges have a magnetoelectric effect. Finally, the thermoelectric properties of graphene are theoretically examined. The results indicate that reducing the carrier scattering suppresses the thermoelectric power and enhances the thermoelectric figure of merit. The fine control of the Fermi energy position is thought to be key for the practical use of graphene as a thermoelectric material, which could be achieved with epitaxial graphene. All of these results reveal that epitaxial graphene is physically interesting.
Collapse
Affiliation(s)
- H Kageshima
- NTT Basic Research Laboratories, Nippon Telegraph and Telephone Corporation, Atsugi, Kanagawa, Japan.
| | | | | |
Collapse
|
39
|
Bresnehan MS, Hollander MJ, Wetherington M, LaBella M, Trumbull KA, Cavalero R, Snyder DW, Robinson JA. Integration of hexagonal boron nitride with quasi-freestanding epitaxial graphene: toward wafer-scale, high-performance devices. ACS NANO 2012; 6:5234-5241. [PMID: 22545808 DOI: 10.1021/nn300996t] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Hexagonal boron nitride (h-BN) is a promising dielectric material for graphene-based electronic devices. Here we investigate the potential of h-BN gate dielectrics, grown by chemical vapor deposition (CVD), for integration with quasi-freestanding epitaxial graphene (QFEG). We discuss the large scale growth of h-BN on copper foil via a catalytic thermal CVD process and the subsequent transfer of h-BN to a 75 mm QFEG wafer. X-ray photoelectron spectroscopy (XPS) measurements confirm the absence of h-BN/graphitic domains and indicate that the film is chemically stable throughout the transfer process, while Raman spectroscopy indicates a 42% relaxation of compressive stress following removal of the copper substrate and subsequent transfer of h-BN to QFEG. Despite stress-induced wrinkling observed in the films, Hall effect measurements show little degradation (<10%) in carrier mobility for h-BN coated QFEG. Temperature dependent Hall measurements indicate little contribution from remote surface optical phonon scattering and suggest that, compared to HfO(2) based dielectrics, h-BN can be an excellent material for preserving electrical transport properties. Graphene transistors utilizing h-BN gates exhibit peak intrinsic cutoff frequencies >30 GHz (2.4× that of HfO(2)-based devices).
Collapse
Affiliation(s)
- Michael S Bresnehan
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | | | | | | | | | | | | | | |
Collapse
|
40
|
Nyakiti LO, Myers-Ward RL, Wheeler VD, Imhoff EA, Bezares FJ, Chun H, Caldwell JD, Friedman AL, Matis BR, Baldwin JW, Campbell PM, Culbertson JC, Eddy CR, Jernigan GG, Gaskill DK. Bilayer graphene grown on 4H-SiC (0001) step-free mesas. NANO LETTERS 2012; 12:1749-1756. [PMID: 22352833 DOI: 10.1021/nl203353f] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We demonstrate the first successful growth of large-area (200 × 200 μm(2)) bilayer, Bernal stacked, epitaxial graphene (EG) on atomically flat, 4H-SiC (0001) step-free mesas (SFMs) . The use of SFMs for the growth of graphene resulted in the complete elimination of surface step-bunching typically found after EG growth on conventional nominally on-axis SiC (0001) substrates. As a result heights of EG surface features are reduced by at least a factor of 50 from the heights found on conventional substrates. Evaluation of the EG across the SFM using the Raman 2D mode indicates Bernal stacking with low and uniform compressive lattice strain of only 0.05%. The uniformity of this strain is significantly improved, which is about 13-fold decrease of strain found for EG grown on conventional nominally on-axis substrates. The magnitude of the strain approaches values for stress-free exfoliated graphene flakes. Hall transport measurements on large area bilayer samples taken as a function of temperature from 4.3 to 300 K revealed an n-type carrier mobility that increased from 1170 to 1730 cm(2) V(-1) s(-1), and a corresponding sheet carrier density that decreased from 5.0 × 10(12) cm(-2) to 3.26 × 10(12) cm(-2). The transport is believed to occur predominantly through the top EG layer with the bottom layer screening the top layer from the substrate. These results demonstrate that EG synthesized on large area, perfectly flat on-axis mesa surfaces can be used to produce Bernal-stacked bilayer EG having excellent uniformity and reduced strain and provides the perfect opportunity for significant advancement of epitaxial graphene electronics technology.
Collapse
Affiliation(s)
- L O Nyakiti
- U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Kim M, Hwang J, Shields VB, Tiwari S, Spencer MG, Lee JW. SiC surface orientation and Si loss rate effects on epitaxial graphene. NANOSCALE RESEARCH LETTERS 2012; 7:186. [PMID: 22410299 PMCID: PMC3323459 DOI: 10.1186/1556-276x-7-186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/29/2011] [Accepted: 03/12/2012] [Indexed: 05/31/2023]
Abstract
We have explored the properties of SiC-based epitaxial graphene grown in a cold wall UHV chamber. The effects of the SiC surface orientation and silicon loss rate were investigated by comparing the characteristics of each formed graphene. Graphene was grown by thermal decomposition on both the silicon (0001) and carbon (000-1) faces of on-axis semi-insulating 6H-SiC with a "face-down" and "face-up" orientations. The thermal gradient, in relation to the silicon flux from the surface, was towards the surface and away from the surface, respectively, in the two configurations. Raman results indicate the disorder characteristics represented by ID/IG down to < 0.02 in Si-face samples and < 0.05 in C-faces over the 1 cm2 wafer surface grown at 1,450°C. AFM examination shows a better morphology in face-down surfaces. This study suggests that the optimum configuration slows the thermal decomposition and allows the graphene to form near the equilibrium. The Si-face-down orientation (in opposition to the temperature gradient) results in a better combination of low disorder ratio, ID/IG, and smooth surface morphology. Mobility of Si-face-down orientation has been measured as high as approximately 1,500 cm2/Vs at room temperature. Additionally, the field effect transistors have been fabricated on both Si-face-down and C-face-down showing an ambipolar behavior with more favorable electron conduction.
Collapse
Affiliation(s)
- Moonkyung Kim
- School of Electrical and Computer Engineering, Cornell University, 410 Thurston Avenue, Ithaca, NY 14850-2488, USA
| | - Jeonghyun Hwang
- School of Electrical and Computer Engineering, Cornell University, 410 Thurston Avenue, Ithaca, NY 14850-2488, USA
| | - Virgil B Shields
- School of Electrical and Computer Engineering, Cornell University, 410 Thurston Avenue, Ithaca, NY 14850-2488, USA
| | - Sandip Tiwari
- School of Electrical and Computer Engineering, Cornell University, 410 Thurston Avenue, Ithaca, NY 14850-2488, USA
| | - Michael G Spencer
- School of Electrical and Computer Engineering, Cornell University, 410 Thurston Avenue, Ithaca, NY 14850-2488, USA
| | - Jo-Won Lee
- Department of Convergence Nanoscience, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul, 133-791, South Korea
| |
Collapse
|