Phase transformation on CdSe thin films under annealing in Ar+Se-2 atmosphere

Cubic CdSe thin films of approximately 2000 Angstrom thickness have been pr epared onto glass substrates by chemical bath deposition. The samples were annealed in an Ar + Se-2 atmosphere at normal pressure for 30 h at differen t temperatures in the range of 50-500 degrees C, in order to per-form the c rystalline phase transformation from cubic zincblende (ZB) to the hexagonal wurtzite (W) structure. The characterization of samples included both opti cal absorption and X-ray diffraction analyses, The optical absorption spect ra allowed to calculate the energy band-gap (E-g) values and, hence, the ev olution of E-g in the thermally treated samples through the transformation from the cubic crystalline phase to the hexagonal phase. The X-ray diffract ion spectra also showed the complete microstructural transformation from as -grown cubic samples up to the entire hexagonal lattice for samples with hi gher annealing, The critical point of the ZB --> W transformation is propos ed to occur at 355 +/- 25 degrees C. (C) 2000 Elsevier Science Ltd. All rig hts reserved.