Preparation and Characterization of High Quality Zinc Oxide Thin Films for Optoelectronic Applications

In many respects, zinc oxide (ZnO) exhibits superior optical properties, high exciton binding energy and low production cost. It has been investigated for many potential applications as optoelectronic semiconductor materials. In this report, ZnO semiconductor layers were prepared on transparent glass substrates using e-beam evaporator system under various annealing and oxygen flow conditions. Alumina was employed as the dielectric film layer. The glass substrates were cleaned successively by acetone, alcohol and de-ionized pure water. The evaporator chamber pressure was pumped down to about 5-10 × 10-6 torr at the first step. It was then balanced at about 4-5 × 10-5 torr during the evaporation step while maintained at room temperature. The film deposition rate has been nominally 5 nm/s. After preparation, the films of 100 nm in thickness were transmitted above 75-85% in the visible light wavelength range. The crystalline structural characteristics were revealed by X-ray diffraction (XRD) analysis. Fundamental XRD spectroscopy showed two distinct peaks at 30.4° and 35.2°, corresponding to (100) and (002) crystalline planes. The film also exhibited high c-axis orientation. Their narrow full widths at half-maximum property suggested high crystalline quality for properly annealed ZnO thin films. The optoelectronic behavior would have been presented and discussed for new device applications.