  The low activation energy associated with amorphous chalcogenide structures
offers broad tunability of material properties with laser-based or thermal
processing. In this paper, we study near-bandgap laser induced anisotropic
crystallization in solution processed arsenic sulfide. The modified electronic
bandtail states associated with laser irritation lead to a distinctive
photoluminescence spectrum, compared to thermally annealed amorphous glass.
Laser crystalized materials exhibit a periodic subwavelength ripples structure
in transmission electron microscopy experiments and show polarization dependent
photoluminescence. Analysis of the local atomic structure of these materials
using laboratory-based X-ray pair distribution function analysis indicates that
laser irradiation causes a slight rearrangement at the atomic length scale,
with a small percentage of S-S homopolar bonds converting to As-S heteropolar
bonds. These results highlight fundamental differences between laser and
thermal processing in this important class of materials.
