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Title: Structural and vibrational investigations of Nb-doped TiO{sub 2} thin films

Highlights: • We studied the evolutions of structure for TiO{sub 2} thin film as changes with Nb doping and temperatures. • Up to 800 °C, the grain size of Nb{sub 0.1}Ti{sub 0.9}O{sub 2} is smaller than for pure TiO{sub 2} because doped Nb hinders the growth of the TiO{sub 2} grains. • There was no formation of the rutile phase at high temperature. • Nb doped TiO{sub 2} films have high electron densities at 400–700 °C. • Nb dope extends the absorbance spectra of TiO{sub 2} which leads to the band gap reduce. - Abstract: Acid-catalyzed sol–gel and spin-coating methods were used to prepare Nb-doped TiO{sub 2} thin film. In this work, we studied the effect of niobium doping on the structure, surface, and absorption properties of TiO{sub 2} by energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray reflectometry (XRR), X-ray photoelectron spectroscopy (XPS), Raman, and UV–vis absorption spectroscopy at various annealing temperatures. EDX spectra show that the Nb:Ti atomic ratios of the niobium-doped titania films are in good agreement with the nominal values (5 and 10%). XPS results suggest that charge compensation is achieved by the formation of Ti vacancies. Specific niobium phases are not observed, thus confirming thatmore » niobium is well incorporated into the titania crystal lattice. Thin films are amorphous at room temperature and the formation of anatase phase appeared at an annealing temperature close to 400 °C. The rutile phase was not observed even at 900 °C (XRD and Raman spectroscopy). Grain sizes and electron densities increased when the temperature was raised. Nb-doped films have higher electron densities and lower grain sizes due to niobium doping. Grain size inhibition can be explained by lattice stress induced by the incorporation of larger Nb{sup 5+} ions into the lattice. The band gap energy of indirect transition of the TiO{sub 2} thin films was calculated to be about 3.03 eV. After niobium doping, it decreased to 2.40 eV.« less
Authors:
 [1] ;  [2] ; ;  [3] ; ; ;  [1] ;  [3] ;  [4] ;  [5]
  1. Institute of Physics and Technology, Mongolian Academy of Sciences, Enkhtaivan Avenue 54B, Ulaanbaatar 13330 (Mongolia)
  2. (Russian Federation)
  3. LUNAM Université, Université du Maine, CNRS UMR 6283, Institut des molécules et matériaux et du Mans–IMMM, Avenue Olivier Messiaen, Le Mans 72085 Cedex 9 (France)
  4. Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30013, Taiwan (China)
  5. Frank Laboratory of Neutron Physics, JINR, Dubna 141980 (Russian Federation)
Publication Date:
OSTI Identifier:
22420669
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Research Bulletin; Journal Volume: 60; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION SPECTROSCOPY; ANNEALING; CRYSTAL LATTICES; DOPED MATERIALS; ELECTRON DENSITY; EV RANGE; GRAIN SIZE; NIOBIUM IONS; RAMAN SPECTROSCOPY; SOL-GEL PROCESS; STRESSES; TEMPERATURE DEPENDENCE; THIN FILMS; TITANIUM OXIDES; VACANCIES; X-RAY DIFFRACTION; X-RAY PHOTOELECTRON SPECTROSCOPY; X-RAY SPECTROSCOPY