Phase transformation on CdSe thin films under annealing in Ar+Se2 atmosphere Original Research Article

Cubic CdSe thin films of approximately 2000 Å thickness have been prepared onto glass substrates by chemical bath deposition. The samples were annealed in an Ar+Se2 atmosphere at normal pressure for 30 h at different temperatures in the range of 50–500°C, in order to perform the crystalline phase transformation from cubic zincblende (ZB) to the hexagonal wurtzite (W) structure. The characterization of samples included both optical absorption and X-ray diffraction analyses. The optical absorption spectra allowed to calculate the energy band-gap (Eg) values and, hence, the evolution of Eg in the thermally treated samples through the transformation from the cubic crystalline phase to the hexagonal phase. The X-ray diffraction spectra also showed the complete microstructural transformation from as-grown cubic samples up to the entire hexagonal lattice for samples with higher annealing. The critical point of the ZB→W transformation is proposed to occur at 355±25°C.