Optical and electrical properties of RF-sputtered AZO thin films for space optical applications

Abstract

Transparent conductive oxides (TCOs) are of considerable interest for optical and optoelectronic applications requiring both high optical transparency and electrical conductivity. Among these materials, aluminum-doped zinc oxide (AZO) has emerged as a promising alternative to indium tin oxide (ITO) because of its low cost, elemental abundance, and favorable optical properties. In this work, AZO thin films were deposited on borosilicate glass substrates by radio frequency (RF) magnetron sputtering under different deposition conditions to investigate the influence of processing parameters on their optical, electrical, and surface properties. The films were characterized using spectroscopic ellipsometry, UV–Vis–NIR spectrophotometry, atomic force microscopy (AFM), and four-point probe measurements. To evaluate their environmental durability, the deposited films were subjected to a controlled temperature and humidity cycle, followed by repeat optical and electrical characterization. The results demonstrate that the RF-sputtered AZO thin films maintained high optical transparency and low reflectance while exhibiting deposition-dependent electrical properties. Humidity exposure produced only limited changes in the optical performance, whereas the electrical properties exhibited greater sensitivity to environmental exposure. These findings demonstrate the potential of RF-sputtered AZO thin films as transparent conductive coatings for future space optical applications.