Structure of Se-rich As-Se glasses by high-resolution x-ray photoelectron spectroscopy

To establish the validity of various proposed structural models, we have investigated the structure of the binary AsxSe100-x chalcogenide glass family (x≤40) by high-resolution x-ray photoelectron spectroscopy. From the composition dependence of the valence band, the contributions to the density of states from the 4p lone pair electrons of Se and the 4p bonding states and 4s electrons of Se and As are identified in the top part of the band. The analysis of Se 3d and As 3d core-level spectra supports the so-called chain crossing model for the atomic structure of Se-rich AsxSe100-x bulk glasses. The results also indicate small deviations (∼3-8%) from this model, especially for glass compositions with short Se chains (25<x≤40). For example, the presence of As-As homopolar defect bonds in the stoichiometric As40Se60 and of Se-Se-Se fragments in a glass with composition x=30 is established