Conclusions
Studies of photoinduced phenomena in chalcogenide
glasses continue to be carried out with the aim of completely
understanding the electron-atom(ion) interaction
in amorphous semiconductors and of developing novel
applications. The present status for respective phenomena
can be summarized as follows. For the phase-change
phenomenon, the initial and the fina! structural state
are known, and the main problem is shifting towards
understanding transient characteristics appearing in the
ps-ns regions. For the bulk reversible changes, it has been
demonstrated that the configuration-coordinate models
provide useful insights, although real structural entities
are difficult to identify. Sub-bandgap illumination effects
open up the possibilities of novel applications, although
these effects cast doubts upon the nature of the bandgap
in amorphous semiconductors. For the photoelectro-ionic
phenomena, Lhe mechanisms seem to be understood at a
phenomenological level, and, in the future, these studies
will focus upon microscopic features.