Optical Properties of Nonstoichiometric Tantalum Oxide TaO{sub x} (x < 5/2) According to Spectral-Ellipsometry and Raman-Scattering Data

• Published in: Optics and spectroscopy Vol. 124; no. 6
• Main Authors: Kruchinin, V. N., Volodin, V. A., Perevalov, T. V., Gerasimova, A. K., Aliev, V. Sh, Gritsenko, V. A.
• Format: Journal Article
• Language: English
• Published: United States 15-06-2018
• Subjects: ABSORPTION; COMPUTERIZED SIMULATION; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; DIELECTRIC MATERIALS; DISPERSIONS; ELLIPSOMETRY; ENERGY BEAM DEPOSITION; ION BEAMS; NANOSTRUCTURES; PHOTONS; RAMAN EFFECT; REFRACTIVE INDEX; SPECTRA; TANTALUM OXIDES
• ISSN: 0030-400X; 1562-6911
• DOI: 10.1134/S0030400X18060140

Optical properties of amorphous nonstoichiometric tantalum-oxide films of variable composition (TaO{sub x}, x = 1.94–2.51) in the spectral range of 1.12–4.96 eV, obtained by ion-beam sputtering-deposition of metallic tantalum at different partial oxygen pressures (0.53–9.09 × 10{sup –3} Pa), have been investigated. It is shown by spectral ellipsometry that the character of dispersion of the absorption coefficient and refractive index in TaO{sub x} of variable composition suggests that light-absorbing films with dispersion similar to that in metals are formed at oxygen pressures in the growth chamber below 2.21 × 10{sup –3} Pa, whereas transparent films with dielectric dispersion are formed at pressures above 2.81 × 10{sup –3} Pa. According to the data of quantumchemical simulation, the absorption peak at a photon energy of 4.6 eV in TaO{sub x} observed in the absorptioncoefficient dispersion spectrum is due to oxygen vacancy. The peak in the Raman-scattering spectra of TaO{sub x} films with metallic dispersion at frequencies of 200–230 cm{sup –1} is presumably related to tantalum nanoclusters.