Abstract
We report in this work the optical and structural properties of iron diselenide films (FeSe
2) obtained by selenization under vacuum of amorphous iron oxide films predeposited by spray pyrolysis. The structure of the FeSe
2 films was investigated by scanning electron microscopy (SEM), microprobe analyses, atomic force microscopy (AFM) and X-ray diffraction (XRD). XRD and micro-probe analyses showed that FeSe
2 as well as FeSe
2−
x
phases begin to appear at a selenization temperature of 500 °C. As the selenization temperature rises, the iron diselenide films become more stoichiometric with a dominance of the FeSe
2 phase. At 550 °C, a single FeSe
2 phase having good crystallinity was obtained. At 600 °C, two phases were detected: the major one corresponds to Fe
3O
4, and the minor one to FeSe
2. SEM surface views show that FeSe
2 films have granular structure with small spherical crystallites. However, layered and clustered FeSe
2 films were found, respectively, at 550 °C and 600 °C. Absorption measurements show that iron diselenide films have a direct and an indirect gaps of about 1.03 eV and 0.3 eV, which were suggested to be due to the stoichiometric FeSe
2 phase and to a Fe-rich non-stoichiometric phase, respectively.