Quantum confinement analysis of nanostructures in oxidation of SiGe alloys

We report the investigation on the oxidation behaviour of Si_1-xGe_x alloys (x=0.05, 0.15, and 0.25). It was found for the first time that a nanocap (thickness: 1.6－2.0nm) was formed on the oxide film after fast oxidation. Some new peaks in photoluminescence spectra were discovered, which could be related to the Ge nanocap, the Ge nanolayer (thickness: 0.8－1.2nm) and the Ge nanoparticles (with various diameters from 2.6nm to 7.4nm), respectively. A suitable model and several new calculating formulae combined with the Unrestricted Hartree－Fock－Roothaan (UHFR) method and quantum confinement analysis have been proposed to interpret the PL spectra and the nanostructure mechanism in the oxide and Ge segregation.