PHOTOLUMINESCENCE MEASUREMENTS IN THE PHASE-TRANSITION REGION FOR CDSTHIN-FILMS

CdS polycrystalline thin films were grown by the chemical bath deposit ion technique at 80 degrees C onto glass substrates. The films grow in the cubic crystalline structure as determined by x-ray diffraction an alysis. After thermal annealing in S-2 and Ar atmospheres, the CdS cha nges from the metastable zinc blende phase to a stable wurtzite one. T he cubic-to-hexagonal transition temperature has been determined to be 370 degrees C, as seen by the photoluminescence spectra and the x-ray diffraction patterns of the different samples. These spectra show the well-known green emission band of the CdS centered at 2.4 eV for the as-grown sample, which shifts to 2.25 eV for the sample annealed at 36 5 degrees C just before the phase transition takes place. For the samp le annealed at 374 degrees C, an abrupt blueshift of the green band oc curs going back to an energy value of 2.4 eV, when the crystalline pha se transition occurs. (C) 1996 American Vacuum Society.