Growth and Characterization of High-Quality Dielectric Sputtered Zinc Oxide Films from the First Principle

Abstract

In this article, we investigate the effect of thermal treatment on a piezoelectric material, zinc oxide, which has found numerous applications in sensors and actuators. Even though the exact mechanisms rendering electrical properties are less known, we suspect that the thermal treatments are responsible for improvement of electrical characteristics of the deposited thin films. We establish that the thermal agitation is responsible for improvement of orders of magnitude in electrical characteristics of sputtered ZnO thin films. The surface quality of the thin films deposited is process dependent. ZnO films were deposited using a dielectric sputtering method, on oxidized silicon 100 n-type wafers. Further, these films were thermally annealed in oxygen ambient at 600 °C in a tube furnace with 2 mL/min pressure. It is observed that, after thermal annealing, the quality of the films is improved by orders of magnitude. The luminance, crystalline quality, and surface morphology of these thin films was measured with atomic force microscopy, scanning electron microscopy with BSD detector (BSD-SEM), and Fourier transform infrared spectroscopy (FTIR). The results infer that the film’s surface is very smooth and dense. The surface roughness is improved by 1.3149 nm from 7.882 nm prior to thermal annealing to post-annealing surface roughness with 6.5671 nm. Post-thermal annealing process reveals average grain size was 50 nanometers; the surface roughness is reduced to 6.5671 nm. A significant improvement in electrical current-voltage characteristics was recorded with I-V curve. It is suspected to be due to substantial enhancement in electrical conductivity as a result of thermal treatment and improved spectral response recorded a FTIR peak shift of 1 wave number in total. The FTIR peak shift is suspected to be due to evaporation and reduction in oxygen vacancies due to thermal annealing process. The post-annealed ZnO films will be used for actuation in the future.