Oxygen isotopic tracing study of the dry thermal oxidation of 6H SiC

The (0 0 0 1) and (0 0 0 (1) over bar) faces of 6H SiC have been oxidised s equentially at 1100 degrees C and 100 mbar in ultra-dry oxygen of natural i sotopic concentration and in ultra-dry oxygen highly enriched in O-18. Meas urement of the O-18 isotopic concentration profiles by nuclear resonance pr ofiling with the narrow resonance at 151 keV in O-18(p,alpha)N-15 shows tha t on the carbon-terminated face (0 0 0 (1) over bar) the oxidation mechanis m is rather similar to that observed on S(1 0 0), but that on the silicon-t erminated face (0 0 0 1) the surface isotopic exchange and oxide formation are superposed. The surface exchange observed during a third dry oxidation, in O-16(2), is very similar in magnitude and spatial extent on S(1 0 0), a nd the two 6H SIC faces, suggesting that at least near the surface the natu re and composition of the three oxides are very similar. (C) 2000 Elsevier Science B.V. All rights reserved.