Characterization of structural, optical and electrical properties of Ni doped ZnO thin films

Abstract

Zinc Oxide (ZnO) and Nickel (Ni) doped ZnO (Zn1-xNixO) thin films (x= 0%, 1%, 3%, 5%, 10%, 15%) have been prepared by spray pyrolysis method on to glass substrate at 300 0C. The structural, optical and electrical properties of the asdeposited films are studied in details. The energy dispersive X-ray (EDX) data of the films were taken. EDX result reveals that the deposited films are very close to the nominal composition. The scanning electron microscope (SEM) micrographs of the Zn1-xNixO films have been taken for different compositions deposited on glass substrate at the temperature 300 0C. The SEM micrographs of as-deposited films show deposition covers the substrate well. X-ray diffraction pattern has been recorded on as-deposited Zn1-xNixO thin films. The as-deposited film has a broad peak with six identified peaks indicating the films amorphous with crystalline in nature. Lattice constants have been calculated using the prominent peaks of (100) and (002) the average value obtained are a =3.22 Å and c=5.17 Å. Structure of the material has been identified as hexagonal. Grain size of thin film was determined from (100). Grain size of the film decreases with the increase of Ni concentration from (1%-5%) of Ni then increases slightly. A secondary phase of NiO has been observed in higher Ni concentration sample excess doping of Ni. Various optical constants such as absorbance, transmittance, refractive index, extension coefficient and optical conductivity of the films have been studied. For different compositions of as-deposited Zn1-xNixO films, the band gap varies from 3.38 to 2.80 eV. The electrical resistivity measurements were made on number of films from the room temperature up to 440K. The resistivity of the films gradually decreases with the increase of temperature, which indicates the semiconducting nature of the materials. Resistivity also decreases with the increasing doping concentration.