We proposed a new explanation of photo-induced volume changes in chalcogenide glasses.
In our computer simulation we observed covalent bond breaking in the network caused
by excited electrons, whereas holes contribute to the formation of inter-chain bonds.
The interplay between photo-induced bond breaking and inter-chain bond formation leads
to either volume expansion or shrinkage. In the non-ideal case, only a part of the
processes is reversible and the total expansion includes the reversible and irreversible
changes. Finally we investigate the structural properties of flatly and obliquely
deposited chalcogenide thin films. Different void sizes can cause different photoinduced
volume changes.
