Effect of Annealing Temperature on Structural, Photoluminescence and Photoconductivity Properties of ZnO Thin Film Depos
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RESEARCH ARTICLE
Effect of Annealing Temperature on Structural, Photoluminescence and Photoconductivity Properties of ZnO Thin Film Deposited on Glass Substrate by Sol–Gel Spin Coating Method Mohd. Mubashshir Hasan Farooqi1 • Rajneesh Kumar Srivastava1
Received: 22 August 2017 / Revised: 22 December 2018 / Accepted: 9 January 2019 The National Academy of Sciences, India 2019
Abstract In this work, zinc oxide (ZnO) thin films have been deposited on glass substrate using a simple and inexpensive multi-step sol–gel spin coating method at annealing temperatures of 300, 400, 500 and 600 C in an open atmosphere. The influence of annealing on structural, photoluminescence and photoconductivity properties of ZnO thin films has been systematically investigated. X-ray diffraction pattern reveals that all ZnO thin films are polycrystalline with hexagonal wurtzite structure. Scanning electron micrograph depicted the formation of ZnO nanofibrous structure. Photoluminescence properties of ZnO thin films have been investigated by photoluminescence spectroscopy at room temperature. Photoconductivity properties have been investigated in terms of several parameters such as voltage dependence of photocurrent and dark current as well as time-resolved rise and decay of photocurrent. The rise and decay spectra under periodic illumination show reproducible and stable photoresponse. The synthesized ZnO thin film seems to be having potential use in UV– Vis photodetectors. Keywords Photoconductivity Photoluminescence ZnO Thin film Sol–gel XRD Fibrous root morphology
& Rajneesh Kumar Srivastava [email protected] Mohd. Mubashshir Hasan Farooqi [email protected] 1
Department of Electronics and Communication, University of Allahabad, Allahabad 211002, India
1 Introduction ZnO is an important semiconductor material for a variety of optoelectronic and piezoelectric device applications. Wide direct band gap (3.37 eV), large exciton binding energy (60 meV) and excellent chemical and thermal stability of ZnO at room temperature ensure its suitability for a variety of applications such as LEDs, solar cells and gas sensors [1–3]. In thin film form, ZnO materials have attracted a great deal of attention, primarily due to their potential applications as photodetectors, piezoelectric transducers, optical waveguides, non-volatile memory, surface acoustic wave devices, conductive gas sensors, pH sensors, biosensors, transparent conductive electrodes, solar cell windows and varistors [4, 5], etc. Specifically, ZnO has attracted a great deal of attention for its ultraviolet light detection properties in nanostructures including nanoparticles, nanorods and nanowires [6, 7]. Photoconductivity, increase in electrical conductivity of certain materials when they are exposed to light of sufficient energy, serves as a tool to understand the internal processes in these materials, and it is also widely used to detect the presence of light and to measure its intensity in light-sensitive devices [8]. In order for photoconductivity to be pro
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