Effect of high-energy electron beam irradiation on the properties of ZnO thin films prepared by magnetron sputtering

Abstract

In this work we demonstrate that high-energy electron beam irradiation (HEEBI) performed in air at room temperature affects remarkably the electrical, optical, and structural properties of undoped ZnO films prepared on SiO2 substrates by magnetron sputtering techniques. Hall and photoluminescence measurements revealed that the p-type conductivity was realized in HEEBI treated films with low dose of 1014 electrons/cm2 and converted to n-type conductivity with further increase in the amount of dose. X-ray photoelectron spectroscopy showed that indiffusion of Si from the substrate as well as N from the ambient into the films took place as a result of HEEBI treatment at high and low doses, respectively. X-ray diffraction analysis indicated that all as-grown films were found to have compressive stress, which was relieved to some extent by HEEBI treatment with high dose of 1016 electrons/cm2. It was also found that better crystallinity with a bigger grain size was observed in HEEBI treated ZnO films with a higher dose. Field emission scanning electron microscope showed that HEEBI treated films with low dose had surface morphologies with big rodlike shapes. The major acceptorlike defects were determined to be oxygen interstitial and zinc vacancy. A model was proposed in terms of O, Zn, N, and Si diffusion to explain the observed results.