Improvements in graphene growth on 4H-SiC(0001) using plasma induced surface oxidation

Abstract

A Si-face 4H-SiC surface was modified by plasma oxidation followed by HF etching. The resulting surface was covered with a carbon overlayer composed of C–C bonded clusters and Si–O–C bonding from Si4C4O4 and Si4C4−xO2 (x < 2), as evidenced by photoemission spectroscopy measurements and wetting properties. A trend was observed in which the thickness of the carbon overlayer was proportional to the SiO2 thickness after plasma oxidation, indicating that the former could be controlled on the subnanometer scale by adjusting plasma conditions. After a subsequent annealing under ultrahigh vacuum, we found that graphene grew on the modified SiC surface without the formation of a pitting morphology, which is in contrast to the case using an untreated SiC substrate. Raman spectroscopy revealed that the former graphene includes fewer defects than the latter graphene. We discuss the microscopic mechanism by which reaction products composed of C–C and Si–O–C bonds form in the SiO2 film near the SiO2/SiC interface via plasma oxidation as well as their influence on the subsequent growth of graphene.