A comparative photoemission study of polar and nonpolar SiC surfaces oxidized in N 2O

Abstract

Photoemission studies of oxidized SiC samples grown ex situ in N 2O, at a temperature of 900 °C, on the (0 0 0 1), (0 0 0 1̄), (1 1 2̄ 0) and (1 0 1̄ 0) surfaces are reported. Angle resolved data from the Si 1s and Si 2p core levels and the Si KL 2,3L 2,3 Auger transitions are analyzed and compared to data from a sample grown in O 2 on the (0 0 0 1) surface. The results show oxide growth and no oxy-nitride formation. The growth rate is found to be smallest for the Si-terminated (0 0 0 1) surface and highest for the nonpolar (1 0 1̄ 0) surface. The presence of two oxidation states, Si +4 and a suboxide, are required to explain and model recorded Si 1s, Si 2p and Si KLL spectra. The SiO 2 shift is found to be smaller on the (0 0 0 1) surface than on the other three surfaces, which is attributed to an oxide thickness dependence of the shift. A layer attenuation model describes satisfactorily the intensity variations observed in the core level components versus electron emission angle when assuming the suboxide at the interface. Estimates made of the thickness of the oxide layers show that the oxidation rate for the (0 0 0 1) surfaces is about half of that for the (1 0 1̄ 0) surface and that the oxidation rate for the (1 1 2̄ 0) and (0 0 0 1̄) surfaces are similar but somewhat smaller than for the (1 0 1̄ 0) surface. The amount of suboxide is found to be smaller on the nonpolar than on the polar surfaces.