An XPS study of the early stages of silver photodiffusion in Ag/a-As2S3 films

X-ray induced structural changes at the Ag/As2S3 interface are investigated using X-ray photoelectron spectroscopy on the samples prepared within the spectrometer. The as-prepared film consists of stable heteropolar As-S bonds as well as similar to 16% S (and As) atoms in lower (higher) electron density configurations such as the -S-S-(-As-As-) segments with 'wrong' homopolar bonds. Two distinct stages of the X-ray induced diffusion are revealed. At first, silver reacts with atoms within -S-S- like segments to form Ag-S bonds. In the second stage, the Ag-S bonds decompose due to the reaction of S with As atoms within the -As-As- 'wrong' segments to form As-S heteropolar bonds, and silver diffuses away from the interface into the film. The results provide guideline for enhancing silver photodiffusion in chalcogenide glass. The irradiation of the (Ag-Te)/As2S3 sample with X-rays shows that not only Ag, but Te also diffuses away from the surface. (c) 2006 Elsevier B.V. All rights reserved.