Reversible structural changes of in situ prepared As 40 Se 60 nanolayers studied by XPS spectroscopy

As40Se60 nanolayers, as-deposited, annealed and in situ illuminated by green (532 nm) laser light, were studied using synchrotron radiation photoelectron spectroscopy. Changes in composition and local atomic coordination occurring in the irradiated region of As40Se60 films were monitored by analysis of As 3d and Se 3d core levels. It was found that the thermal treatment causes a decrease of the concentration of homopolar (As–As and Se–Se) bonds. On the other hand, an increasing concentration of both As-rich and Se-rich structural units (s.u.) with homopolar As–As and Se–Se bonds was observed under in situ green laser illumination of As40Se60 nanolayers. This process appeared to be reversible for a few sequences of annealing and illuminating of the sample. After a few cycles storing at ambient conditions the As40Se60 film composition was gradually changing, i.e. the aging effect was detected due to a drastic loss of As under ambient conditions. The surface local structure of the As40Se60 nanolayers and their photoinduced transformation are discussed in detail.