Preparation and optical properties of Ta2O5−x thin films

Thin films of tantalum pentoxide (Ta2O5−x) were deposited on glass substrates by RF magnetron sputtering under different Ar/O2 flow ratios. Characterization of the coatings was investigated by UV–vis spectroscopy, ellipsometry (at a wavelength of 632.8 nm), Fourier transform infrared (FTIR) spectroscopy, atomic force microscope (AFM), and transmission electron microscope energy dispersive spectrometer (TEMEDS). It was obtained that the Ta2O5−x films produced with different Ar/O2 ratios ranging from 10/6 to 8/10 exhibit good visible optical transmissions, 80–90%. The optical band gap of the films from 10/6 to 8/10 decreased from 4.25 to 3.70 eV from the transmission spectra. The film thickness decreased from 108.1 to 99.4 nm and refractive index increased from 2.02 to 2.15 for the films produced with different Ar/O2 ratios ranging from 10/6 to 8/10. In addition, the results indicate that the films prepared at high Ar/O2 flow ratios (8/10) have featureless peak of suboxide for FTIR spectra and exhibit atomic ratio Ta:O = 1:2.41 for TEMEDS analysis.