  Under irradiation of amorphous $As_{x}Se_{100-x}$ films by band-gap light, it
was observed that lateral mass transport of the film material changed the
direction of movement in the region (4 < x < 5 at%.) of topological structural
transition (crossover "from light to dark" to "from dark to light"). We propose
a model that qualitatively describes the observed phenomenon. In experimental
testing of the model by Kelvin probe force microscopy, for the first time to
our knowledge, it was detected that with the increase of temperature (from
ambient to glass-transition temperature, Tg) photo-induced mass transport in
glassy semiconductors occurs with the rates, which significantly exceed those
at room temperature.
