Electronic properties of the crystalline phases of the As2Te3-GeTe system

The electronic properties of the crystalline layered phases As2GenTe3+n of the system As2Te3-GeTe have been experimentally studied by X-ray photo-elec tron spectroscopy (XPS), X-ray absorption spectroscopy (XAS) and Te-125 Mos sbauer spectroscopy The results are discussed from a tight-binding calculat ion. First, we show that Te-125 Mossbauer spectroscopy and XAS at the L-I edge o f tellurium can be combined to analyse the local electronic structure of th e Te atoms. The shapes of the Mossbauer spectra and of the first XAS peak a re explained from the existence of two very different local environments fo r the Te atoms which are found inside and at the edges of the layers, respe ctively Then, we present a reconstruction of the total density of states of As2Te3, including both the valence and the bottom of the conduction bands, based on the XPS and XAS experimental results and a tight-binding calculat ion. This analysis allows us to recognize the different atomic contribution s to each experimental peak. Finally we show that the XPS valence bands of the As2GenTe3+n compounds change with increasing n because of the increasin g number of Ge-Te bonds compared to the number of As-Te bonds.