SI0.57GE0.43 ALLOY LAYERS IMPLANTED WITH OXYGEN - SPUTTERING YIELDS AND ATOMIC COMPOSITION DEPTH PROFILES

Si0.57Ge0.43 alloy layers implanted with O+ ions have been investigated by Rutherford backscattering spectrometry. The layers of 550 nm thickness were grown by molecular beam epitaxy on an n-type Si(100) substrate (rho = 5-20-OMEGA-cm). The samples were subsequently implanted with 200 keV O+ ions to doses of 0.6 x 10(18), 1.2 x 10(18) and 1.8 x 10(18) O+ cm-2 at a substrate temperature of about 500-degrees-C. Experimental sputtering yields and atomic composition depth profiles were determined by making comparisons of the spectra of Rutherford backscattering spectrometry collected before and after implantation. We find no evidence for preferential sputtering as the ratio (1.36) of the experimental rates of 0.15 Si atoms per ion (+/- 10%) and 0.11 Ge atoms per ion (+/- 10%) compares well with the ratio of the alloy composition (1.33) of the samples. Similar values for the sputter rates, calculated by computer simulation (TRIM), have been achieved by optimizing the values of surface binding energy and lattice binding energy to 3 eV and 1.5 eV respectively. The depth profiles of silicon, germanium and oxygen have been calculated from the spectra of Rutherford backscattering spectrometry and the procedure used for this three-element system is described. The oxygen distribution is a skew gaussian at low doses whilst for the highest dose it is flat topped and broad