The electronic structure of Cu-modified arsenic chalcogenides

X-ray photoelectron and emission spectroscopies have been used to study the electronic structure of Cux(As2S3)1−x and Cux(As2Se3)1−x compounds across the range where the amount of Cu in the sample strongly affects the photodarkening (PD). Shifts of the As 3d, S 2p and Se 3d core level energies in Cu-containing samples indicate Cu bonding to As as well as to the chalcogen atoms. These shifts are largest in the selenide compounds. Low-temperature (∼0.4 K) anomalies and vectoral photoinduced effects are found to be much less affected by the Cu addition than is the PD.