Structural and optical characterization of CdS films grown by photochemical deposition

CdS thin films are grown by photochemical deposition from an aqueous solution and characterized by x-ray diffraction (XRD), Raman spectroscopy, photoluminescence measurement, and optical transmission spectroscopy. The films are deposited at room temperature and annealed at temperatures up to 500 degrees C. The as-deposited film is dominantly zinc blende cubic. The cubic phase remains dominant until the annealing temperature becomes higher than 400 degrees C. By the annealing at 450 degrees C, the XRD pattern turns to that of hexagonal phase. Moreover, its peak width decreases and the near-band-edge luminescence begins to be observed. The band gap is decreased by annealing below 400 degrees C and then abruptly increased by the annealing at 450 degrees C. This annealing behavior of the band gap is interpreted considering the quantum size effects, the band tail due to disorder, and the cubic-hexagonal transition. (C) 1999 American Institute of Physics. [S0021-8979(99)05310-4].