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

Cubic CdSe thin films of approximately 2000 Angstrom thickness have been prepared onto glass substrates by chemical bath deposition. The samples were annealed in an Ar + Se-2 atmosphere at normal pressure for 30 h at different temperatures in the range of 50-500 degrees C, in order to per-form 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 (E-g) values and, hence, the evolution of E-g 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 degrees C. (C) 2000 Elsevier Science Ltd. All rights reserved.