Experimental evidence of the low-temperature formation of gamma-In2Se3 thin films obtained by a solid-state reaction

In2Se3 coatings were obtained by a solid-state reaction, induced by annealing, between the In and Se constituents sequentially deposited in thin film form. The films crystallized in the gamma-In2Se3 phase. To confirm and to characterize this phase, the films have been investigated by microprobe analysis and X-ray photoelectron spectroscopy, transmission electron microscopy and X-ray diffraction, Raman diffusion and optical absorption measurements. It is shown that selected area diffraction (SAD) patterns of the gamma-In2Se3 phase are obtained and that a very good correlation exists between the planes obtained from X-ray spectra and SAD patterns. Raman diffusion and optical absorption also lead to characteristic data of the gamma-In2Se3 phase, and are compared with the values of the other phases. Moreover it is shown that the occurrence of the gamma-phase is related to the annealing under selenium atmosphere and to the initial Se/In atomic ratio.