Composition and chemical states of the plasma anodised film on Ge

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Abstract
Anodisation of a germanium surface was carried out successfully in oxygen plasma excited by a high-frequency (500 kHz) electromagnetic field in a quartz reactor. The refractive index of the oxygen plasma anodised (OPA) film on Ge(111) is generally 1.66-1.68 ( lambda =6328 AA). The chemical composition and chemical states of the Ge-OPA film have been analysed using Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) with argon ion sputtering. There is GeO2 on the surface of the OPA film. In the bulk of the OPA film, there is mainly GeO2 and some unoxidised germanium. The distribution of O and Ge is fundamentally homogeneous in the bulk. There are double peaks for Ge(3d) in the XPS of the Ge-OPA film after argon ion sputtering. The binding energy of 32.7 eV is due to the Ge in GeO2, and that of 29.2 eV corresponds to a few unoxidised Ge atoms in the OPA film. The chemical stoichiometry of the OPA film is very similar to that of vitreous GeO2.