EFFECTS OF SUBSTRATE TEMPERATURE ON STRUCTURAL, OPTICAL AND SURFACE MORPHOLOGICAL PROPERTIES OF PULSED LASER DEPOSITED ZnO THIN FILMS

The effect of substrate temperature on the structural, optical and morphological properties of ZnO thin films has been investigated. ZnO thin films were deposited on quartz substrate for various temperatures ranging from room temperature to 250°C by pulsed laser deposition (PLD) technique. Nd:YAG laser (532 nm, 100 mJ, 6 ns, 10 Hz) with corresponding fluence of 6 J/cm2 was employed for the ablation of ZnO target. Characterization of the thin films was carried out using X-ray diffraction (XRD), high resolution UV-visible spectrometer, atomic force microscope (AFM) and scanning electron microscope (SEM). From XRD analysis, the amorphous behaviors of films at room temperature and crystalline behavior along the preferred orientation of (002) is exhibited for higher substrate temperature. The transmittances of grown films increase with the increasing substrate temperature. The evaluated values of bandgap energies increase with increasing substrate temperature up to the range of 150°C and then monotonically decrease with the further increase in temperature. AFM and SEM analysis illustrates that the density and height of grains for deposited films increase significantly with increasing substrate temperature.