Photoinduced changes in the local structure of a-GeSe2 by in situ EXAFS

In-situ extended x-ray absorption fine structure (EXAFS) analysis at the Ge and Se k-edges has been used to study the changes in the local atomic structure induced by bandgap and super bandgap illumination in normally and obliquely deposited a-GeSe2 films. The results obtained before, during and after illumination show that both the transient and metastable changes are induced by illumination, the magnitude depending on the photon energy and also the deposition conditions. A contraction is observed at both the Se and the Ge nearest neighbour distances.