Raman Topography and Strain Uniformity of Large-Area Epitaxial Graphene

Epitaxial graphene homogeneity and quantum Hall effect in millimeter-scale devices

Quantized magnetotransport is observed in 5.6 x 5.6 mm^2 epitaxial graphene devices, grown using highly constrained sublimation on the Si-face of SiC(0001) at high temperature (1900 °C). The precise quantized Hall resistance of Rxy = h/2e^2 is maintained up to record level of critical current Ixx = 0.72 mA at T = 3.1 K and 9 T in a device where Raman microscopy reveals low and homogeneous strain. Adsorption-induced molecular doping in a second device reduced the carrier concentration close to the Dirac point(n ~ 1E10 (1/cm^2)), where mobility of 43700 cm^2/Vs is measured over an area of 10 mm^…

外延石墨烯纳米带周期性阵列中纳米尺度太赫兹电导率与太赫兹等离子体超快动力学

Nanoscale Terahertz Conductivity and Ultrafast Dynamics of Terahertz Plasmons in Periodic Arrays of Epitaxial Graphene Nanoribbons

本文利用太赫兹光谱和扫描近场显微镜，研究了外延石墨烯纳米带中太赫兹等离子体的超快动力学，揭示了光激发后载流子温度在约7 ps内从超过5000 K降至晶格温度、迁移率基本不变，并发现缺陷势垒和边缘散射对载流子输运的影响。

Film structure of epitaxial graphene oxide on SiC: Insight on the relationship between interlayer spacing, water content, and intralayer structure

Chemical oxidation of multilayer graphene grown on silicon carbide yields films exhibiting reproducible characteristics, lateral uniformity, smoothness over large areas, and manageable chemical complexity, thereby opening opportunities to accelerate both fundamental understanding and technological applications of this form of graphene oxide films. Here, we investigate the vertical inter-layer structure of these ultra-thin oxide films. X-ray diffraction, atomic force microscopy, and IR experiments show that the multilayer films exhibit excellent inter-layer registry, little amount (<10%) of int…

Encapsulation and Electronic Control of Epitaxial Graphene by Photosensitive Polymers and UV light

Electronic devices using epitaxial graphene on Silicon Carbide require encapsulation to avoid uncontrolled doping by impurities deposited in ambient conditions. Additionally, interaction of the graphene monolayer with the substrate causes relatively high level of electron doping in this material, which is rather difficult to change by electrostatic gating alone. Here we describe one solution to these problems, allowing both encapsulation and control of the carrier concentration in a wide range. We describe a novel heterostructure based on epitaxial graphene grown on silicon carbide combined wi…

Photo-physics and electronic structure of lateral graphene/MoS2 and metal/MoS2 junctions

Integration of semiconducting transition metal dichalcogenides (TMDs) into functional optoelectronic circuitries requires an understanding of the charge transfer across the interface between the TMD and the contacting material. Here, we use spatially resolved photocurrent microscopy to demonstrate electronic uniformity at the epitaxial graphene/molybdenum disulfide (EG/MoS2) interface. A 10x larger photocurrent is extracted at the EG/MoS2 interface when compared to metal (Ti/Au) /MoS2 interface. This is supported by semi-local density-functional theory (DFT), which predicts the Schottky barrie…

Large-Area High-Throughput Identification and Quality Control of Graphene and Few-Layer Graphene: Prospects of Industry-Scale Applications

Practical applications of graphene require a reliable high-throughput method of graphene identification and quality control, which can be used for large-scale substrates and wafers. We have proposed and experimentally tested a fast and fully automated approach for determining the number of atomic planes in graphene samples. The procedure allows for in situ identification of the borders of the regions with the same number of atomic planes. It is based on an original image processing algorithm, which utilizes micro-Raman calibration, light background subtraction, lighting non-uniformity correcti…

采用化学气相沉积技术在SiO₂衬底上可控生长大面积双层MoS₂薄膜

Controlled Growth of large area bilayer MoS$_2$ films on SiO$_2$ substrates by chemical vapour deposition technique

本研究针对大面积均匀双层TMD薄膜制备难题，通过调控CVD前驱体流动模式，在无衬底等离子体处理下制备出平方毫米级双层MoS₂薄膜，表征验证了其结构特性，制备的FET器件开关比达10⁶，为激子器件发展提供了材料基础。