Friday, February 17, 2017

Abstract-Multi-scale investigations of interface properties, stacking order and decoupling of few layer graphene on C-face 4H-SiC

  • a Terahertz Materials Analysis Center, Department of Physics, Chemistry and Biology, IFM, Linköping University, Linköping, S-58183 SE, Sweden
  • b MaxLab, Lund University, S-22100 Lund, Sweden
  • c Department of Physics, Chemistry and Biology, IFM, Linköping University, Linköping, S-58183 SE, Sweden
  • d CNR-IMM, Strada VIII, 5, 95121 Catania, Italy
  • e Department of Electrical Engineering and Center for Nanohybrid Functional Materials, University of Nebraska-Lincoln, Lincoln, NE 68588, USA

In this work, we report a muti-scale investigation using several nano-, micro and macro-scale techniques of few layer graphene (FLG) sample consisting of large monolayer (ML) and bilayer (BL) areas grown on C-face 4H-SiC (000-1) by high-temperature sublimation. Single 1 × 1 diffraction patterns are observed by micro-low-energy electron diffraction for ML, BL and trilayer graphene with no indication of out-of-plane rotational disorder. A SiOxlayer is identified between graphene and SiC by X-ray photoelectron emission spectroscopy and reflectance measurements. The chemical composition of the interface layer changes towards SiO2 and its thickness increases with aging in normal ambient conditions. The formation mechanism of the interface layer is discussed. It is shown by torsion resonance conductive atomic force microscopy that the interface layer causes the formation of non-ideal Schottky contact between ML graphene and SiC. This is attributed to the presence of a large density of interface states. Mid-infrared optical Hall effect measurements revealed Landau-level transitions in FLG that have a square-root dependence on magnetic field, which evidences a stack of decoupled graphene sheets. Contrary to previous works on decoupled C-face graphene, our BL and FLG are composed of ordered decoupled graphene layers without out-of-plane rotation.

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