Formation of Germanium Dioxide During Wet Oxidation of Si0.5 Ge0.5 Alloy

TLDR: In this paper, the authors investigated the oxidation of Si 0.5 Ge 0.5 alloy over the temperature range 800 to 1000°C and determined the composition of the oxide layers by 1.5 MeV Rutherford backscattering spectroscopy (RBS), IR and X-ray XPS.

Abstract: The oxidation of Si 0.5 Ge 0.5 alloy has been investigated over the temperature range 800 to 1000°C . The composition of the oxide layers has been determined by 1.5 MeV Rutherford backscattering spectroscopy (RBS), infrared transmission spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS). During the initial stage of oxidation, as the temperature ramps up in an oxidising ambient both Si and Ge are oxidized to form a mixed oxide in the region near the surface. Upon further oxidation, at temperatures higher than 900°C and times longer than 5 minutes, the Ge atoms are ejected by the growing oxide layer, which has the composition of Si0 2 , and accumulate in the underlying alloy, which becomes rich in Ge.The surface oxide layer remains unchanged. The proportion of Ge0 2 in the near surface region, determined from IR spectra, decreases when the temperatures increases from 800°C to 1000°C. It is concluded that at 800°C Ge atoms are insufficiently mobile to be ejected from the growing oxide and both matrix species ( Si and Ge ) have equal probabilities of oxidation leading to the formation an oxide of composition Si 0.5 Ge 0.5 O 2 . Supporting experiments confirm that Ge0 2 in the surface layer is formed during warm up of the samples oxidized at 900 and 1000°C.