Investigation of neodymium rare earth element doping in spray-coated zinc oxide thin films

Abstract

In recent years, ZnO films are among the preferred transparent conductive oxides because of their advantageous properties such as being nontoxic, low cost and abundant in nature. In this study, undoped and Nd doped ZnO films were produced on microscope glass substrates with the spray pyrolysis technique, which is an economical and easily applicable method, at a substrate temperature of 380 °C. From the X-ray diffraction patterns, the crystal structures of all films have a preferential orientation (002). It is observed from the XRD peak intensities that the ZnO film with a 3% Nd doping has a (100) preferential orientation. The increase in Nd dopant concentration is the reason for changing the preferred direction of the grains completely. The average particle sizes of the films were calculated using Scherrer and Williamson–Hall method. It was determined that the film with 2% Nd doped crystallized better than other films and the largest particle size belongs to this film. The transmittance spectra of Nd doped ZnO films were taken using a UV–Vis spectrophotometer. The optical transmittance spectrum of the films shows that in the visible region, all films have a value of over 90%. Optical band gap values were calculated using these spectra. According to the results obtained, it was determined that the optical band value of the ZnO film decreased first with the Nd contribution, and started to increase when the amount of dopant increased. The surface morphology of the films was analyzed by optical profilometer and surface roughness values were determined. It indicates that the films grown on the glass substrate, as observed in the XRD analysis of the films, consist of nanoscale particles. It has been observed that the surface roughness of the films varies with the increasing amount of Nd. To investigate the surface conditions of the films, the scanned electron microscopy (SEM) images of the obtained films were taken. From the SEM images, it was observed that the surfaces of the films were similar to each other, were nonporous and homogeneous. With this study, the effect of Nd doping on structural, optical and superficial properties of ZnO films was investigated and it was determined that Nd doping of ZnO films were suitable materials for optoelectronic applications.