Characterization of tantalum oxide films grown by pulsed laser deposition

Abstract

Abstract Tantalum oxide (TaOx) films were deposited by KrF excimer laser ablation of Ta2O5 targets in an oxygen gas ambient. The deposition was performed on silicon substrates. The impact of varying the substrate temperature (from room temperature to 400°C) and gas pressure (0.14–5.34 Pa) on film properties was investigated. Differences in composition, with Ta/O ratios in the range 0.36–0.7, were observed when the deposition parameters were varied. For O2 pressures above 2.67 Pa and deposition temperatures of 150°C and higher, Ta/O ratios of 0.38–0.44 were obtained, with a mean value of 0.41. For all growth conditions, based on Auger electron spectroscopy analyses, the tantalum oxide films were found to be homogeneous in composition throughout their thickness. According to X-ray diffraction measurements, the structure of the films was found to be amorphous-like for all temperatures. In terms of optical properties, stoichiometric Ta2O5 films exhibited indices of refraction higher than 2.2, extinction coefficients of less than 10−4, and optical energy band gaps of up to 4.1 eV. Such results showed that Ta2O5 films produced by pulsed laser deposition might be suitable for optical-based applications.