Crystallization and oxidation process of nc-Ge in a-SiO2 matrix from a-Si:H/a-Ge:H multilayers

Abstract Hydrogenated amorphous Si/amorphous Ge (a-Si:H/a-Ge:H) multilayer films were grown by plasma enhanced chemical vapor deposition (PECVD). The as-deposited multilayers were then oxidized with a dry–wet–dry oxidation procedure for different wet oxidation times at 1 atm, 800°C. The changes of microstructure during oxidation were investigated by X-ray diffraction (XRD), Raman scattering and Fourier transformed infrared absorption techniques. It was found that GeSi crystals appeared due to the intermixing between a-Si:H and a-Ge:H sublayers and crystallization in the Ge sublayers. During the oxidation, the Si were preferentially oxidized to form SiO2 while Ge precipitated. Further oxidation (wet oxidation time >60 min) resulted in the oxidation of Ge and finally pure Ge crystals with nanometer scale were formed and embedded in oxide.