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    Effects of substrate temperature and post-deposition anneal on properties of evaporated cadmium telluride films
    (Elsevier Science Sa, 2007) Bacaksız, E.; Basol, B. M.; Altunbaş, M.; Novruzov, V.; Yanmaz, E.; Nezir, S.
    The effects of substrate temperature and post-deposition heat treatment steps on the morphology, structural, optical and electrical properties of thin film CdTe layers grown by vacuum evaporation were investigated. Scanning electron microscopy and X-ray diffraction (XRD) techniques were employed to study the structural changes. It was observed that the grain sizes and morphologies of as-deposited layers were similar for substrate temperatures of - 173 degrees C and - 73 degrees C. However, CdTe films produced at a substrate temperature of 27 degrees C had substantially larger grain size and clearly facetted morphology. Annealing at 200-400 degrees C in air did not cause any appreciable grain growth in any of the films irrespective of their growth temperature. However, annealing at 400 degrees C reduced faceting in all cases and initiated fusing between grains. XRD studies showed that this behavior after annealing at 400 degrees C coincided with an onset of a degree of randomization in the originally strong (I 11) texture of the as-grown layers. Optical band gap measurements showed sharpening of the band-edge upon annealing at 400 degrees C and a band gap value in the range of 1.46-1.49 eV Resistivity measurements indicated that annealing at 400 degrees C in air forms a highly resistive compensated CdTe film. All results point to 400 degrees C to be a critical annealing temperature at which optical, structural and electrical properties of CdTe layers start to change. (c) 2006 Elsevier B.V. All rights reserved.
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    The effects of zinc nitrate, zinc acetate and zinc chloride precursors on investigation of structural and optical properties of ZnO thin films
    (Elsevier Science Sa, 2008) Bacaksız, E.; Parlak, M.; Tomakin, M.; Özcelik, A.; Karakiz, M.; Altunbaş, M.
    ZnO thin films were prepared using zinc chloride, zinc acetate and zinc nitrate precursors by spray pyrolysis technique oil glass substrates at 550 degrees C. Structural and optical properties of ZnO films were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and optical transmittance spectra. Regardless of precursors, ZnO thin films are all in hexagonal crystallographic phase and have to (0 0 2) preferred orientation. SEM images show completely different surface morphologies for each precursor in ZnO thin films. ZnO rod was observed only for zinc chloride precursor. The optical measurements reveal that films have a low transmittance and a direct band gap approximately 3.30 eV, which is very close to band gap of intrinsic ZnO. (C) 2007 Elsevier B.V. All rights reserved.