Influence of substrate temperature on the structural and optical properties of crystalline ZnO films obtained by pulsed spray pyrolysis

Abstract

In this work, we report on the structural and optical properties of ZnO films deposited by pulsed spray pyrolysis at relatively low temperatures, compatiblewith a large variety of substrates and processing technologies. Crystalline ZnO films were deposited onto glass substrates using zinc acetate dihydrate dissolved in distilled water with concentration of 0.2M. The temperature of the substrate was varied in the range Ts = 473–673K with ΔТ = 50 K. Effect of Ts were investigated by scanning electron microscopy, x-ray diffraction and energy dispersive x-ray, and optical spectroscopies. Also, the influence of Ts on the grain size, phase composition, texture quality, coherent scattering domain size, crystal lattice parameters, chemical composition, ransmission coefficient, and the bang gap of the ZnO films were studied. X-ray diffraction analysis revealed that films were polycrystalline with hexagonal phase and showed as preferential orientation (101) at Ts<573 K and (100) and (002) at Ts>573 K. Scanning electron microscopy (SEM) measurements showed that the substrate temperature has a strong effect on morphology of the films. Energy dispersive analysis revealed that ZnO films consisted of the non-stoichiometric compounds. Optical measurements showed ZnO films to be highly transparent in the visible region, and optical band gap is shifting from 3.18 eV to 3.30 eV.