Confinement-Controlled Growth of Epitaxial Graphene on Hexagonal SiC with Metal Plate Capping: Enhanced Structural and Carrier Transport Properties

Abstract

The structural and electrical properties of epitaxial graphene (EG) grown on a hexagonal SiC substrate have been significantly enhanced by capping the SiC surface with a molybdenum plate (Mo-plate) during UHV annealing at substantially lower temperature (850-950 ºC) than the conventional high-temperature annealing in UHV or Ar atmosphere (Figure 1). The heat accumulation between SiC surface and Mo-plate by thermal radiation mirroring and the reduced sublimation rate of Si atoms are considered to be the main influences of Mo-plate capping on EG growth. Both can promote cooperatively the favourable environments for growing high-quality EG films at reduced temperature.1 The improved crystallinity of grown EG film was demonstrated by the significant reduction of D-peak and increase of 2D-peak in the measured Raman spectra compared with the spectra for no capping. The carrier transport characteristics of the EG film grown on Si-face surface at ~950 ºC was studied by measuring the channel current of top-gated field effect transistors (FETs) depending on the gate voltage and the magnetotransport with Hall-bar structures. The field effect mobility was measured to be ~1800 cm2/Vs and the Hall mobility be ~2100 cm2/Vs, and the carrier type was found to be n-type in both FET and Hall-bar measurements. The sheet carrier density was estimated to be (3.6-9.2)1012 cm-2 from the Hall-bar measurements. The Quantum Hall Effect was observed only for high filling factors up to 14 T due to the relatively high carrier density. However, clear Shubnikov-de-Haas oscillations were observed, indicating that the carrier scattering due to intrinsic defects is minimal in the EG film grown with Mo-plate capping (Figure 1).