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

Hydrogenated amorphous Si/amorphous Ge (a-Si:H/a-Ge:H) multilayer films wer e grown by plasma enhanced chemical vapor deposition (PECVD). The as-deposi ted multilayers were then oxidized with a dry-wet-dry oxidation procedure f or different wet oxidation times at 1 atm, 800 degrees C. The changes of mi crostructure during oxidation were investigated by X-ray diffraction (XRD), Raman scattering and Fourier transformed infrared absorption techniques. I t 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 Ce preci pitated. Further oxidation (wet oxidation time >60 min) resulted in the oxi dation of Ge and finally pure Ge crystals with nanometer scale were formed and embedded in oxide. (C) 2000 Elsevier Science B.V. All rights reserved.