Investigation on structural, optical and electrical properties of Zn doped indium oxide thin film for gamma dosimetry

Abstract

Zinc-doped indium oxide thin film was deposited on the glass substrate using the spray pyrolysis method at a substrate temperature of 723K for various Zn concentrations in the range of 2–10 at%. The obtained film confirmed a polycrystalline cubic structure with a shift in preferred growth orientation from (400) to (222) on higher doping levels. The morphological study also exhibited a microstructure change which corroborates with the XRD spectra. Moreover, surface morphology has a great influence on the physical properties of the film. Cubic crystallization of doped In2O3 with no impurity phase and the presence of oxygen vacancies is confirmed by Raman spectra. It also confirms the In substitution by Zn. Optical transmittance decreased with doping which is supported by a decrease in bandgap energy from 3.68 to 3.5. The Refractive index is estimated using three different models with the Herve-Vandamme model showing the least deviation. Urbach energy shows an inverse relation with energy band gaps. Violet-blue emission was observed in the photoluminescence spectra. Zn doping also had an influence on the electrical properties of the material. Thermoluminescence spectroscopy validates Zn-doped In2O3 films' suitability for gamma dosimetry. XPS peak intensity corresponds to oxygen vacancies observed to be higher for Zn doped sample relative to undoped, indicates the formation of defects after doping. The resistivity increased up to 6 at% and then decreased, which can be due to the preferred orientation change to (222) at higher dopant concentrations. From the investigation, it is concluded that 4% Zn doped In2O3 can be used for sensor applications due to its good structural, optical and electrical properties and also lesser defects.