The annealing behavior was explained in terms of a reduction in bond-length and bond angle fluctuations (especially the Ge-Se-Ge bond angle) that might be related to changes in the connectivity of GeSe4/2 tetrahedral units; such as the relative proportions of corner-sharing and edge-sharing tetrahedra. It was suggested that these changes resulted from long-range relaxation processes which tended to remove large-scale clustering, rather than from local atomic rearrangements which favored the formation of crystal-like structural units. The results also revealed the existence of a significant gap-state density, which tended to increase during annealing. These gaps were introduced by coordination defects (neutral dangling bonds on Ge and/or Se sites, Se-based charged paired centers) which could not be identified here.

K.M.Kandil, M.F.Kotkata, M.L.Theye, A.Gheorghiu, C.Senemaud, J.Dixmier: Physical Review B, 1995, 51[24], 17565-73