Surface chemistry of Ni induced graphite formation on the 6H-SiC (0001) surface and its implications for graphene synthesis

Ni films ranging in thickness from 0.4 nm to 50 nm were deposited by evaporation onto terraced SiC (0001) substrates at room temperature and annealed at 700 degrees C. The resulting changes in surface composition and morphology were characterized using Auger electron spectroscopy and atomic force microscopy. In all cases, graphitic films dominate the surface chemistry. There appears to be three different thickness dependent morphology regimes. For the thinnest Ni films (0.4 nm), there is a uniform carbon-overlayer. For slightly thicker Ni films (0.6-9.6 nm), clustering and platelet formation are observed, and for still thicker films (50 nm), the platelets give way to hillocks. Within the platelet regime, there is a critical thickness at which surface roughening occurs. These results reveal a potential parametric window in which graphene may be produced and harvested. (C) 2010 Elsevier Ltd. All rights reserved.