Structure–property correlation in epitaxial (200) rutile films on sapphire substrates

• Published in: Journal of solid state chemistry 2012-03, Vol.187, p.231-237
• Main Authors: Bayati, M.R., Joshi, Sh, Molaei, R., Narayan, R.J., Narayan, J.
• Format: Article
• Language: English
• Subjects: 4-chlorophenol; ATOMIC FORCE MICROSCOPY; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; CORRELATIONS; DECOMPOSITION; Defect; DEFECTS; Defects and impurities in crystals; microstructure; EFFICIENCY; ENERGY BEAM DEPOSITION; EPITAXY; Exact sciences and technology; Frequency; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; LASER RADIATION; LAYERS; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; PHOTOCATALYSIS; Photoluminescence; Physics; POINT DEFECTS; Point defects (vacancies, interstitials, color centers, etc.) and defect clusters; PULSED IRRADIATION; Repetition; Roughness; RUTILE; SAPPHIRE; Structure of solids and liquids; crystallography; SUBSTRATES; THIN FILMS; Titania; TITANIUM OXIDES; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION; X-RAY PHOTOELECTRON SPECTROSCOPY
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2012.01.031

We have investigated the influence of the deposition variables on photocatalytic properties of epitaxial rutile films. Despite a large lattice misfit of rutile with sapphire substrate, (200) epitaxial layers were grown on (0001)sapphire by domain matching epitaxy paradigm. Using φ-scan XRD and cross section TEM, the epitaxial relationship was determined to be rutile(100)||sapphire(0001), rutile(001)||sapphire(10−10), and rutile(010)||sapphire(1−210). Based on the XRD patterns, increasing the repetition rate introduced tensile stress along the film normal direction, which may arise as a result of trapped defects. Formation of such defects was studied by UV–VIS, PL, and XPS techniques. AFM studies showed that the film roughness increases with the repetition rate. Finally, photocatalytic performance of the layers was investigated through measuring decomposition rate of 4-chlorophenol on the films surface. The films grown at higher frequencies revealed higher photocatalytic efficiency. This behavior was mainly related to formation of point defects which enhance the charge separation. In this report, epitaxial rutile TiO2 thin films were deposited by PLD process under various deposition rates (frequencies) and their physical and chemical properties, especially photocatalytic performance, were investigated. It was found that photocatalytic efficiency improves when frequency increases. This behavior was mainly related to formation of point defects which enhance the charge separation. [Display omitted] ► Rutile epitaxial thin films were deposited via PLD process under different frequencies. ► Defect characteristic was studied. ► Photocatalytic performance of the layers was investigated.