Structural, optical and photoelectrochemical characterizations of monoclinic Ta3N5 thin films. Issue 37 (27th August 2015)

• Record Type: Journal Article
• Authors: Khan, Sherdil; Zapata, Maximiliano J. M.; Pereira, Marcelo B.; Gonçalves, Renato V.; Strizik, Lukas; Dupont, Jairton; Santos, Marcos J. L.; Teixeira, Sérgio R.
• Is Part Of: Physical chemistry chemical physics. Volume 17:Issue 37(2015)
• Page Start: 23952
• Page End: 23962
• Publication Date: 2015-08-27
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c5cp03645c
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : Monoclinic Ta3 N5 thin films were synthesized by thermal nitridation of directly sputtered Ta2 O5 films. The dielectric constant of Ta3 N5 film was found to be in between 7–9 and its band structure has shown a strong dependence on the pH of the electrolyte. Abstract : Monoclinic Ta3 N5 thin films were synthesized by thermal nitridation of amorphous Ta2 O5 films directly sputtered by radio frequency magnetron sputtering. The samples were studied by high resolution transmission electron microscopy, X-ray photoelectron spectroscopy, UV-Vis-NIR spectrophotometry, rietveld refinements, spectroscopic ellipsometry and electrochemical techniques. The surface composition of Ta3 N5 thin film was found to be different than the underlying film, affecting the optical properties of the material. Rietveld refinement has confirmed that the nitridation process results in Schottky and oxygen substitutional defects within the crystalline structure of monoclinic Ta3 N5 thin film. The optical constants of the film were obtained by spectroscopic ellipsometry within a spectral range of 4.60–0.54 eV, i.e. 270–2300 nm. The suitable parameterization was found to consist of three Tauc–Lorentz and one Lorentz oscillators. The conduction band, valence band and the flat band positions were determined by photoelectrochemical techniques, presenting a strong dependence on pH of the eletrolyte. Improved photocurrent was obtained in alkaline conditions and attributed to the shorter depletion region width measured by Mott–Schottky and the lower recombination life time measured by open circuit potential decay analyses.