Improved thermal stability of GaN{0001} surfaces by adsorbed C60 molecules

Abstract

Adsorption and desorption of C60 molecules on GaN{0001}-1×1 surfaces as well as the surface decomposition by heating were investigated with Auger electron spectroscopy. The first monolayer of C60 forms strong chemical bonds to the substrate atoms. A seven-step annealing procedure at temperatures up to 1275 K is presented which completely removes the adsorbed carbon without decomposing the surface. If the process is applied to clean, uncovered GaN{0001}-1×1 surfaces thermal etching with a significant Ga atom loss is observed. The results indicate that adsorbed C60 increases the thermal stability of the surfaces considerably and that thermal etching begins at defects or steps at the surface where the molecules are most strongly bound.