It was noted that thin films which were grown by using the co-called flash evaporation method exhibited stoichiometric deviations; with anion vacancies and excess Cu. These changes in composition produced a variation in the band structure. The effects of compositional variations and anion vacancies upon the energy gap were analyzed, and a schematic band level arrangement was deduced. Samples with lower numbers of anions exhibited conduction band minima and valence band maxima which were lower than those in samples with higher numbers of anions. The variation in the valence band maxima was greater than in the conduction band minima.

R.Díaz, M.León: Journal of Vacuum Science and Technology A, 1995, 13[6], 2803-7