CVD growth of SiC on sapphire substrate and graphene formation from the epitaxial SiC

摘要

6H-SiC epi-layer was grown on c-plane sapphire by chemical vapor deposition (CVD) and epitaxial graphene was grown on the SiC film using the thermal decomposition method. A thin (～300 nm) A1N was employed as a buffer layer since a direct growth on sapphire did not produce SiC. Raman spectroscopy, x-ray diffraction (XRD), and atomic force microscopy (AFM) confirmed the growth of high quality 6H-SiC on the AlN/sapphire at 1450℃. The effect of AlN growth method/condition (HVPE and MBE) on the quality of final SiC film and epitaxial graphene was explored. Raman and XRD 29-scan did not show any significant difference between the SiC films grown on HVPE-AlN and MBE-AlN. A sharper XRD rocking curve was observed on the SiC/HVPE-AlN but a smoother SiC was grown on the MBE-AlN. Graphitization of the SiC/AlN/sapphire was done at 1300-1400℃ under Ultra High Vacuum (UHV). The SiC on MBE-AlN survived at high temperatures (up to 1400℃) without cracking and graphene was grown on it. However, the SiC on HVPE-AlN cracked and peeled off at 1300℃ resulting in no formation of graphene. The signatures of graphene were clearly observed by Raman spectroscopy with the 2D-peak to G-peak intensity (I_(2D)/I_G) of approximately 2, the D-peak to G-peak intensity (I_D/I_G) of 0.4, and the 2D-peak width of 55 cm~(-1).