Aggregation of carbon atoms at SiO2/SiC(0 0 0 1) interface by plasma oxidation toward formation of pit-free graphene

The deposition of carbon is the key to yielding pit-free graphene terraces on SiC(0 0 0 1) surfaces. We present a novel technique to form a carbon overlayer at the monolayer scale on a SiC(0 0 0 1) Si-face substrate involving plasma oxidation at atmospheric pressure followed by HF etching, both of which are performed at near room temperature. We discuss the mechanism by which carbon atoms aggregate at the SiO2/SiC interface, which occurs in plasma oxidation but not in conventional thermal oxidation. We subsequently anneal the SiC surface with additional carbon atoms in vacuum to grow graphene. Its surface morphology exhibits few pits on terraces with widths of approximately 500 nm, in strong contrast to graphene grown on SiC after simple HF cleaning. This is probably due to carbon clusters deposited on SiC assisting the nucleation of more uniform buffer layers over the surface, which suppresses the vertical sublimation of Si prior to graphene growth.