Electronic structure of Ge–As–Te glasses Original Research Article

The electronic structure of Ge0.2Te0.8 and Ge0.1AsxTe0.9−x glasses with x=0.2, 0.46 and 0.54 has been experimentally determined by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The values of the Ge 3p3/2, As 3p3/2 and Te 3d5/2 core level binding energy do not vary significantly within this series of glasses in agreement with the covalent character of the bonds. The atomic contributions to the main observed peaks in the XPS valence bands and XAS spectra are obtained from a molecular calculation. This approach is first used for crystalline As2Te3 and compared to a periodic tight-binding calculation in order to check its accuracy for the analysis of the experimental data in terms of local environments. The electronic structure of Ge0.2Te0.8 is consistent with the existence of GeTe4 units connected by Te–Te bonds but does not rule out the presence of Ge–Ge bonds. The XPS valence bands of the ternary glasses are formed by two broad bands which are due to the s- and p-type valence electrons of the different atoms, respectively. Increase of the As content mainly changes the p-type peak and the main XAS peaks at the As K and Ge K edges. These changes are due to the decrease in the number of As–Te bonds and the increase in the number of As–As bonds.