Characterization of tantalum oxide films grown by pulsed laser deposition

Tantalum oxide (TaOx) films were deposited by KrF excimer laser ablation of Ta2O5 targets in an oxygen gas ambient. The deposition was performed on si licon substrates. The impact of varying the substrate temperature (from roo m temperature to 400 degrees C) and gas pressure (0.14-5.34 Pa) on film pro perties was investigated. Differences in composition, with Ta/O ratios in t he range 0.36-0.7, were observed when the deposition parameters were varied . For O-2 pressures above 2.67 Pa and deposition temperatures of 150 degree s C and higher, Ta/O ratios of 0.35-0.44 were obtained, with a mean value o f 0.41. For all growth conditions, based on Auger electron spectroscopy ana lyses, the tantalum oxide films were found to be homogeneous in composition throughout their thickness. According to X-ray diffraction measurements, t he structure of the films was found to be amorphous-like for all temperatur es. In terms of optical properties, stoichiometric Ta2O5 films exhibited in dices of refraction higher than 2.2, extinction coefficients of less than 1 0(-4), and optical energy band gaps of up to 4.1 eV. Such results showed th at Ta2O5 films produced by pulsed laser deposition might be suitable for op tical-based applications. (C) 1999 Elsevier Science S.A. All rights reserve d.