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Lu Q, Le C, Zhang X, Cook J, He X, Zarenia M, Vaninger M, Miceli PF, Singh DJ, Liu C, Qin H, Chiang TC, Chiu CK, Vignale G, Bian G. Dirac Fermion Cloning, Moiré Flat Bands, and Magic Lattice Constants in Epitaxial Monolayer Graphene. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2200625. [PMID: 35446987 DOI: 10.1002/adma.202200625] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 04/14/2022] [Indexed: 06/14/2023]
Abstract
Tuning interactions between Dirac states in graphene has attracted enormous interest because it can modify the electronic spectrum of the 2D material, enhance electron correlations, and give rise to novel condensed-matter phases such as superconductors, Mott insulators, Wigner crystals, and quantum anomalous Hall insulators. Previous works predominantly focus on the flat band dispersion of coupled Dirac states from different twisted graphene layers. In this work, a new route to realizing flat band physics in monolayer graphene under a periodic modulation from substrates is proposed. Graphene/SiC heterostructure is taken as a prototypical example and it is demonstrated experimentally that the substrate modulation leads to Dirac fermion cloning and, consequently, the proximity of the two Dirac cones of monolayer graphene in momentum space. Theoretical modeling captures the cloning mechanism of the Dirac states and indicates that moiré flat bands can emerge at certain magic lattice constants of the substrate, specifically when the period of modulation becomes nearly commensurate with the ( 3 × 3 ) R 30 o \[(\sqrt 3 \; \times \;\sqrt 3 )R{30^o}\] supercell of graphene. The results show that epitaxial single monolayer graphene on suitable substrates is a promising platform for exploring exotic many-body quantum phases arising from interactions between Dirac electrons.
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Affiliation(s)
- Qiangsheng Lu
- Department of Physics and Astronomy, University of Missouri, Columbia, MO, 65211, USA
| | - Congcong Le
- RIKEN Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS), Wako, Saitama, 351-0198, Japan
| | - Xiaoqian Zhang
- Department of Physics and Astronomy, University of Missouri, Columbia, MO, 65211, USA
- Department of Physics, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Jacob Cook
- Department of Physics and Astronomy, University of Missouri, Columbia, MO, 65211, USA
| | - Xiaoqing He
- Electron Microscopy Core Facility, University of Missouri, Columbia, MO, 65211, USA
- Department of Mechanical and Aerospace Engineering, University of Missouri, Columbia, MO, 65211, USA
| | - Mohammad Zarenia
- Department of Physics and Astronomy, University of Missouri, Columbia, MO, 65211, USA
| | - Mitchel Vaninger
- Department of Physics and Astronomy, University of Missouri, Columbia, MO, 65211, USA
| | - Paul F Miceli
- Department of Physics and Astronomy, University of Missouri, Columbia, MO, 65211, USA
| | - David J Singh
- Department of Physics and Astronomy, University of Missouri, Columbia, MO, 65211, USA
| | - Chang Liu
- Department of Physics, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Hailang Qin
- Department of Physics, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Tai-Chang Chiang
- Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, IL, 61801-3080, USA
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, 104 South Goodwin Avenue, Urbana, IL, 61801-2902, USA
| | - Ching-Kai Chiu
- RIKEN Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS), Wako, Saitama, 351-0198, Japan
| | - Giovanni Vignale
- Department of Physics and Astronomy, University of Missouri, Columbia, MO, 65211, USA
| | - Guang Bian
- Department of Physics and Astronomy, University of Missouri, Columbia, MO, 65211, USA
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Oh S, Seo J, Choi G, Lee HS. Understanding adsorption geometry of organometallic molecules on graphite. Sci Rep 2021; 11:18497. [PMID: 34531487 PMCID: PMC8446079 DOI: 10.1038/s41598-021-97978-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Accepted: 08/26/2021] [Indexed: 11/18/2022] Open
Abstract
To comprehensively investigate the adsorption geometries of organometallic molecules on graphene, Cp*Ru+ fragments as an organometallic molecule is bound on highly oriented pyrolytic graphite and imaged at atomic resolution using scanning tunneling microscopy (STM) (Cp* = pentamethylcyclopentadienyl). Atomic resolution imaging through STM shows that the Cp*Ru+ fragments are localized above the hollow position of the hexagonal structure, and that the first graphene layer adsorbed with the fragments on the graphite redeveloped morphologically to minimize its geometric energy. For a better understanding of the adsorption site and molecular geometry, experimental results are compared with computed calculations for the graphene surface with Cp*Ru+ fragments. These calculations show the adsorption geometries of the fragment on the graphene surface and the relationship between the geometric energy and molecular configuration. Our results provide the chemical anchoring geometry of molecules on the graphene surface, thereby imparting the theoretical background necessary for controlling the various properties of graphene in the future.
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Affiliation(s)
- Seungtaek Oh
- Department of Materials Science and Chemical Engineering, Hanyang University, Ansan, Gyeonggi, 15588, Republic of Korea.,BK21 FOUR ERICA-ACE Center, Hanyang University, Ansan, Gyeonggi, 15588, Republic of Korea
| | - Jungyoon Seo
- Department of Materials Science and Chemical Engineering, Hanyang University, Ansan, Gyeonggi, 15588, Republic of Korea.,BK21 FOUR ERICA-ACE Center, Hanyang University, Ansan, Gyeonggi, 15588, Republic of Korea
| | - Giheon Choi
- Department of Materials Science and Chemical Engineering, Hanyang University, Ansan, Gyeonggi, 15588, Republic of Korea.,BK21 FOUR ERICA-ACE Center, Hanyang University, Ansan, Gyeonggi, 15588, Republic of Korea
| | - Hwa Sung Lee
- Department of Materials Science and Chemical Engineering, Hanyang University, Ansan, Gyeonggi, 15588, Republic of Korea. .,BK21 FOUR ERICA-ACE Center, Hanyang University, Ansan, Gyeonggi, 15588, Republic of Korea.
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Bocquet FC, Lin YR, Franke M, Samiseresht N, Parhizkar S, Soubatch S, Lee TL, Kumpf C, Tautz FS. Surfactant-Mediated Epitaxial Growth of Single-Layer Graphene in an Unconventional Orientation on SiC. PHYSICAL REVIEW LETTERS 2020; 125:106102. [PMID: 32955317 DOI: 10.1103/physrevlett.125.106102] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Revised: 01/08/2020] [Accepted: 07/08/2020] [Indexed: 06/11/2023]
Abstract
We report the use of a surfactant molecule during the epitaxy of graphene on SiC(0001) that leads to the growth in an unconventional orientation, namely R0° rotation with respect to the SiC lattice. It yields a very high-quality single-layer graphene with a uniform orientation with respect to the substrate, on the wafer scale. We find an increased quality and homogeneity compared to the approach based on the use of a preoriented template to induce the unconventional orientation. Using spot profile analysis low-energy electron diffraction, angle-resolved photoelectron spectroscopy, and the normal incidence x-ray standing wave technique, we assess the crystalline quality and coverage of the graphene layer. Combined with the presence of a covalently bound graphene layer in the conventional orientation underneath, our surfactant-mediated growth offers an ideal platform to prepare epitaxial twisted bilayer graphene via intercalation.
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Affiliation(s)
- F C Bocquet
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - Y-R Lin
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
- Experimentalphysik IV A, RWTH Aachen University, Otto-Blumenthal-Straße, 52074 Aachen, Germany
| | - M Franke
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
- Experimentalphysik IV A, RWTH Aachen University, Otto-Blumenthal-Straße, 52074 Aachen, Germany
| | - N Samiseresht
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
- Experimentalphysik IV A, RWTH Aachen University, Otto-Blumenthal-Straße, 52074 Aachen, Germany
| | - S Parhizkar
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - S Soubatch
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - T-L Lee
- Diamond Light Source, Ltd., Didcot OX110DE, Oxfordshire, United Kingdom
| | - C Kumpf
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
- Experimentalphysik IV A, RWTH Aachen University, Otto-Blumenthal-Straße, 52074 Aachen, Germany
| | - F S Tautz
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
- Experimentalphysik IV A, RWTH Aachen University, Otto-Blumenthal-Straße, 52074 Aachen, Germany
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Celis A, Nair MN, Sicot M, Nicolas F, Kubsky S, Taleb-Ibrahimi A, Malterre D, Tejeda A. Growth, morphology and electronic properties of epitaxial graphene on vicinal Ir(332) surface. NANOTECHNOLOGY 2020; 31:285601. [PMID: 32244246 DOI: 10.1088/1361-6528/ab866a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Superlattice induced minigaps in graphene band structure due to underlying one-dimensional nanostructuration has been demonstrated. A superperiodic potential can be introduced in graphene if the substrate is periodically structured. The successful preparation of a periodically nanostructured substrate in large scale can be obtained by carefully studying the electronic structure with a spatial averaging technique such as high-energy resolution photoemission. In this work, we present two different growth methods such as temperature programmed growth (TPG) and chemical vapor deposition (CVD) studied by scanning tunnelling microscopy (STM) and low energy electron diffraction (LEED). In both methods, we show that the original steps of Ir(332) have modified with (111) terraces and step bunching after graphene growth. Graphene grows continuously over the terrace and the step bunching areas. We observe that while TPG growth does not give rise to a well-defined surface periodicity required for opening a bandgap, the CVD growth does. By combining with angle-resolved photoemission spectroscopy (ARPES) measurements, we correlate the obtained spatial periodicity to observed band gap opening in graphene.
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Affiliation(s)
- A Celis
- Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, Orsay 91405, France
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5
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Wang J, Hu Y, Chen J, Ye C. Self-assembled CeVO 4/Au heterojunction nanocrystals for photothermal/photoacoustic bimodal imaging-guided phototherapy. RSC Adv 2020; 10:2581-2588. [PMID: 35496088 PMCID: PMC9048972 DOI: 10.1039/c9ra09860g] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Accepted: 01/04/2020] [Indexed: 11/29/2022] Open
Abstract
Phototherapy, including photothermal therapy (PTT) and photodynamic therapy (PDT), has attracted great attention because it can effectively inhibit the proliferation and propagation of cancer cells. Recently, heterojunction nanomaterials have shown tremendous application value in the field of biological medicine. In this work, the CeVO4/Au heterojunction nanocrystals (NCs) are designed for photothermal/photoacoustic bimodal imaging-guided phototherapy. The as-synthesized hydrophobic oleic acid (OA)-stabilized CeVO4 nanosheets were modified with HS-PEG-OH for translating into hydrophilic ones, which can significantly improve their stability and biocompatibility. Subsequently, the plasmonic Au nanoparticles were in situ successfully deposited on the surface of HS-PEG-coated CeVO4 to form CeVO4/Au heterojunction NCs for improving the visible and near-infrared light absorption, which results in enhanced photothermal conversion performance and reactive oxygen species (ROS) generation capacity. Thus, the CeVO4/Au can cause more severe damage to cancer cells than pure CeVO4 under NIR laser irradiation. Also, CeVO4/Au can provide distinct tumor contrast by photothermal/photoacoustic bimodal bioimaging. Our results demonstrate that CeVO4/Au NCs could be used as an effective theranostic anticancer agent for near-infrared (NIR) light-mediated PTT and PDT.
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Affiliation(s)
- Junrong Wang
- Department of Obstetrics and Gynecology, China-Japan Union Hospital of Jilin University Changchun Jilin 130033 China
| | - Yubo Hu
- Department of Anesthesiology, China-Japan Union Hospital of Jilin University Changchun Jilin 130033 China
| | - Junyang Chen
- Department of Anesthesiology, China-Japan Union Hospital of Jilin University Changchun Jilin 130033 China
| | - Cong Ye
- Department of Obstetrics and Gynecology, China-Japan Union Hospital of Jilin University Changchun Jilin 130033 China
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Mazza AR, Miettinen A, Daykin AA, He X, Charlton TR, Conrad M, Guha S, Lu Q, Bian G, Conrad EH, Miceli PF. Revealing interfacial disorder at the growth-front of thick many-layer epitaxial graphene on SiC: a complementary neutron and X-ray scattering investigation. NANOSCALE 2019; 11:14434-14445. [PMID: 31334737 DOI: 10.1039/c9nr03504d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Epitaxial graphene on SiC provides both an excellent source of high-quality graphene as well as an architecture to support its application. Although single-layer graphene on Si-face SiC has garnered extensive interest, many-layer graphene produced on C-face SiC could be significantly more robust for enabling applications. Little is known, however, about the structural properties related to the growth evolution at the buried interface for thick many-layer graphene. Using complementary X-ray scattering and neutron reflectivity as well as electron microscopy, we demonstrate that thick many-layer epitaxial graphene exhibits two vastly different length-scales of the buried interface roughness as a consequence of the Si sublimation that produces the graphene. Over long lateral length-scales the roughness is extremely large (hundreds of Å) and it varies proportionally to the number of graphene layers. In contrast, over much shorter lateral length-scales we observe an atomically abrupt interface with SiC terraces. Graphene near the buried interface exhibits a slightly expanded interlayer spacing (∼1%) and fluctuations of this spacing, indicating a tendency for disorder near the growth front. Nevertheless, Dirac cones are observed from the graphene while its domain size routinely reaches micron length-scales, indicating the persistence of high-quality graphene beginning just a short distance away from the buried interface. Discovering and reconciling the different length-scales of roughness by reflectivity was complicated by strong diffuse scattering and we provide a detailed discussion of how these difficulties were resolved. The insight from this analysis will be useful for other highly rough interfaces among broad classes of thin-film materials.
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Affiliation(s)
- A R Mazza
- Department of Physics and Astronomy, University of Missouri, Columbia, Missouri, USA.
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7
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Chang M, Wang M, Chen Y, Shu M, Zhao Y, Ding B, Hou Z, Lin J. Self-assembled CeVO 4/Ag nanohybrid as photoconversion agents with enhanced solar-driven photocatalysis and NIR-responsive photothermal/photodynamic synergistic therapy performance. NANOSCALE 2019; 11:10129-10136. [PMID: 31089645 DOI: 10.1039/c9nr02412c] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The plasmonic cerium vanadate (CeVO4) semiconductor and plasmonic silver (Ag) metal exhibit a localized surface plasmon resonance (LSPR) effect in the visible (Vis)-light region; however, weak absorption in the near-infrared (NIR) region restricts their environmental remediation and biomedical application. Herein, CeVO4/Ag nanohybrids with self-assembled heterostructure and improved Vis/NIR light absorption were synthesized from CeVO4 nanosheets and AgNO3 solution, which could serve as potential solar-driven catalytic agents and near-infrared (NIR) light responsive anticancer agents. Oleic acid-stabilized CeVO4 nanosheets were modified with the HS-PEG1000-OH by the thiol-ene click reaction and presented self-assembly morphology in aqueous solution due to hydrophobic-hydrophobic interactions. Sulfhydryl (-SH) groups provided stable sites for Ag+ ions on the surface of CeVO4, and Ag+ ions could be directly reduced by Ce3+ ions to form CeVO4/Ag heterojunction nanocrystals (NCs). Due to the higher absorption in the Vis/NIR light region than CeVO4 nanosheets, CeVO4/Ag NCs led to the improved solar light responsive photocatalytic degradation of organic dyes. Upon the exposure of these NCs to an 808 nm laser, CeVO4/Ag NCs show high photothermal conversion efficiency, ROS generation ability and photoacoustic (PA) signal for implementing PA imaging-guided photothermal/photodynamic synergistic cancer therapy with better tumor inhibition effect.
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Affiliation(s)
- Mengyu Chang
- State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China. and University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Meifang Wang
- State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China. and University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Yeqing Chen
- School of Applied Physics and Materials, Wuyi University, Jiangmen 529020, PR China
| | - Mengmeng Shu
- Department of Periodontology, Stomatological Hospital, Jilin University, Changchun 130021, PR China
| | - Yajie Zhao
- State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China. and University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Binbin Ding
- State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China. and University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Zhiyao Hou
- State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China. and Affiliated Cancer Hospital & Institute of Guangzhou Medical University, Key Laboratory of Protein Modification and Degradation, School of Basic Medical Sciences, Guangzhou Medical University, Guangzhou 511436, PR China.
| | - Jun Lin
- State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China. and University of Science and Technology of China, Hefei, Anhui 230026, China and Affiliated Cancer Hospital & Institute of Guangzhou Medical University, Key Laboratory of Protein Modification and Degradation, School of Basic Medical Sciences, Guangzhou Medical University, Guangzhou 511436, PR China.
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8
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Xu X, Liu C, Sun Z, Cao T, Zhang Z, Wang E, Liu Z, Liu K. Interfacial engineering in graphene bandgap. Chem Soc Rev 2018. [PMID: 29513306 DOI: 10.1039/c7cs00836h] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Graphene exhibits superior mechanical strength, high thermal conductivity, strong light-matter interactions, and, in particular, exceptional electronic properties. These merits make graphene an outstanding material for numerous potential applications. However, a graphene-based high-performance transistor, which is the most appealing application, has not yet been produced, which is mainly due to the absence of an intrinsic electronic bandgap in this material. Therefore, bandgap opening in graphene is urgently needed, and great efforts have been made regarding this topic over the past decade. In this review article, we summarise recent theoretical and experimental advances in interfacial engineering to achieve bandgap opening. These developments are divided into two categories: chemical engineering and physical engineering. Chemical engineering is usually destructive to the pristine graphene lattice via chemical functionalization, the introduction of defects, doping, chemical bonds with substrates, and quantum confinement; the latter largely maintains the atomic structure of graphene intact and includes the application of an external field, interactions with substrates, physical adsorption, strain, electron many-body effects and spin-orbit coupling. Although these pioneering works have not met all the requirements for electronic applications of graphene at once, they hold great promise in this direction and may eventually lead to future applications of graphene in semiconductor electronics and beyond.
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Affiliation(s)
- Xiaozhi Xu
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China.
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9
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Hill HM, Rigosi AF, Chowdhury S, Yang Y, Nguyen NV, Tavazza F, Elmquist RE, Newell DB, Hight Walker AR. Probing the dielectric response of the interfacial buffer layer in epitaxial graphene via optical spectroscopy. PHYSICAL REVIEW. B 2017; 96:195437. [PMID: 29541699 PMCID: PMC5846628 DOI: 10.1103/physrevb.96.195437] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Monolayer epitaxial graphene (EG) is a suitable candidate for a variety of electronic applications. One advantage of EG growth on the Si face of SiC is that it develops as a single crystal, as does the layer below, referred to as the interfacial buffer layer (IBL), whose properties include an electronic band gap. Though much research has been conducted to learn about the electrical properties of the IBL, not nearly as much work has been reported on the optical properties of the IBL. In this work, we combine measurements from Mueller matrix ellipsometry, differential reflectance contrast, atomic force microscopy, and Raman spectroscopy, as well as calculations from Kramers-Kronig analyses and density functional theory (DFT), to determine the dielectric function of the IBL within the energy range of 1 eV to 8.5 eV.
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Affiliation(s)
- Heather M Hill
- Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, United States
| | - Albert F Rigosi
- Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, United States
| | - Sugata Chowdhury
- Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, United States
| | - Yanfei Yang
- Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, United States
- Joint Quantum Institute, University of Maryland, College Park, MD 20742, United States
| | - Nhan V Nguyen
- Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, United States
| | - Francesca Tavazza
- Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, United States
| | - Randolph E Elmquist
- Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, United States
| | - David B Newell
- Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, United States
| | - Angela R Hight Walker
- Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, United States
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10
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Role of the Potential Barrier in the Electrical Performance of the Graphene/SiC Interface. CRYSTALS 2017. [DOI: 10.3390/cryst7060162] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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11
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N Nair M, Palacio I, Celis A, Zobelli A, Gloter A, Kubsky S, Turmaud JP, Conrad M, Berger C, de Heer W, Conrad EH, Taleb-Ibrahimi A, Tejeda A. Band Gap Opening Induced by the Structural Periodicity in Epitaxial Graphene Buffer Layer. NANO LETTERS 2017; 17:2681-2689. [PMID: 28345926 DOI: 10.1021/acs.nanolett.7b00509] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The epitaxial graphene buffer layer on the Si face of hexagonal SiC shows a promising band gap, of which the precise origin remains to be understood. In this work, we correlate the electronic to the atomic structure of the buffer layer by combining angle resolved photoemission spectroscopy (ARPES), scanning tunneling microscopy (STM), and high-resolution scanning transmission electron microscopy (HR-STEM). We show that the band structure in the buffer has an electronic periodicity related to the structural periodicity observed in STM images and published X-ray diffraction. Our HR-STEM measurements show the bonding of the buffer layer to the SiC at specific locations separated by 1.5 nm. This is consistent with the quasi 6 × 6 periodic corrugation observed in the STM images. The distance between buffer C and SiC is 1.9 Å in the bonded regions and up to 2.8 Å in the decoupled regions, corresponding to a 0.9 Å corrugation of the buffer layer. The decoupled regions are sp2 hybridized. Density functional tight binding (DFTB) calculations demonstrate the presence of a gap at the Dirac point everywhere in the buffer layer, even in the decoupled regions where the buffer layer has an atomic structure close to that of graphene. The surface periodicity also promotes band in the superperiodic Brillouin zone edges as seen by photoemission and confirmed by our calculations.
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Affiliation(s)
- Maya N Nair
- UR1 CNRS/Synchrotron SOLEIL, Saint-Aubin, 91192 Gif sur Yvette, France
- Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Bât. 510 , F-91405 Orsay Cedex, France
| | - Irene Palacio
- UR1 CNRS/Synchrotron SOLEIL, Saint-Aubin, 91192 Gif sur Yvette, France
| | - Arlensiú Celis
- Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Bât. 510 , F-91405 Orsay Cedex, France
- Synchrotron SOLEIL, L'Orme des Merisiers , Saint-Aubin, 91192 Gif sur Yvette, France
| | - Alberto Zobelli
- Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Bât. 510 , F-91405 Orsay Cedex, France
| | - Alexandre Gloter
- Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Bât. 510 , F-91405 Orsay Cedex, France
| | - Stefan Kubsky
- Synchrotron SOLEIL, L'Orme des Merisiers , Saint-Aubin, 91192 Gif sur Yvette, France
| | - Jean-Philippe Turmaud
- School of Physics, The Georgia Institute of Technology , Atlanta, Georgia 30332-0430, United States
| | - Matthew Conrad
- School of Physics, The Georgia Institute of Technology , Atlanta, Georgia 30332-0430, United States
| | - Claire Berger
- School of Physics, The Georgia Institute of Technology , Atlanta, Georgia 30332-0430, United States
- CNRS/Institut Neél, BP166 , 38042 Grenoble, France
| | - Walter de Heer
- School of Physics, The Georgia Institute of Technology , Atlanta, Georgia 30332-0430, United States
| | - Edward H Conrad
- School of Physics, The Georgia Institute of Technology , Atlanta, Georgia 30332-0430, United States
| | | | - Antonio Tejeda
- Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Bât. 510 , F-91405 Orsay Cedex, France
- Synchrotron SOLEIL, L'Orme des Merisiers , Saint-Aubin, 91192 Gif sur Yvette, France
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