Effect of oxygen partial pressure on microstructural and optical properties of titanium oxide thin films prepared by pulsed laser deposition |
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Affiliation: | 1. Department of Physics and Astronomy, University of Delaware, Newark, DE 19716, USA;2. Department of Material Science and Engineering, University of Delaware, Newark, DE 19716, USA;1. ICB — Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS — Université de Bourgogne, 9, Avenue Alain Savary, BP47870, 21078 Dijon Cedex, France;2. Institut FEMTO-ST, UMR 6174, Université de Franche-Comté, CNRS, ENSMM, UTBM, 32, Avenue de l''observatoire, 25044 Besancon Cedex, France;3. Solid State Electronics, The Ångström Laboratory, Uppsala University, Box 534, 75121 Uppsala, Sweden |
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Abstract: | Nanocrystalline titanium oxide (TiO2) thin films were deposited on silicon (1 0 0) and quartz substrates at various oxygen partial pressures (1 × 10−5 to 3.5 × 10−1 mbar) with a substrate temperature of 973 K by pulsed laser deposition. The microstructural and optical properties were characterized using Grazing incidence X-ray diffraction, atomic force microscopy, UV–visible spectroscopy and photoluminescence. The X-ray diffraction studies indicated the formation of mixed phases (anatase and rutile) at higher oxygen partial pressures (3.5 × 10−2 to 3.5 × 10−1 mbar) and strong rutile phase at lower oxygen partial pressures (1 × 10−5 to 3.5 × 10−3 mbar). The atomic force microscopy studies showed the dense and uniform distribution of nanocrystallites. The root mean square surface roughness of the films increased with increasing oxygen partial pressures. The UV–visible studies showed that the bandgap of the films increased from 3.20 eV to 3.60 eV with the increase of oxygen partial pressures. The refractive index was found to decrease from 2.73 to 2.06 (at 550 nm) as the oxygen partial pressure increased from 1.5 × 10−4 mbar to 3.5 × 10−1 mbar. The photoluminescence peaks were fitted to Gaussian function and the bandgap was found to be in the range ∼3.28–3.40 eV for anatase and 2.98–3.13 eV for rutile phases with increasing oxygen partial pressure from 1 × 10−5 to 3.5 × 10−1 mbar. |
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Keywords: | A. Thin films C. X-ray diffraction D. Microstructure D. Optical properties Laser deposition |
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