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Influence of annealing temperature on structural and optical properties of mesoporous TiO2 thin films prepared by sol-gel templating technique

B. YARMAND1,* , S. K. SADRNEZHAAD2

Affiliation

  1. Department of New Materials, Materials and Energy Research Center, Karaj, Iran
  2. Department of Material Science and Engineering, Sharif University of Technology, Tehran, Iran

Abstract

TiO2 thin films with mesoporous structure were deposited on quartz substrate by sol-gel dip coating. The structural, morphological and optical properties of the films were characterized by X-ray diffraction (XRD), simultaneous thermal analysis (STA), Fourier transform infrared spectroscopy (FT-IR), Brunauer–Emmett–Teller (BET), atomic force microscopy (AFM), transmission electron microscopy (TEM) and UV/Vis transmittance spectroscopy. Crystallization of the anatase phase was initiated at 300°C. Its transformation to the rutile phase occurred at 700°C. Anatase and rutile crystallites initially sized 3.2 and 15.3nm, respectively. The anatase phase was under tension; but the rutile phase was under compression. Increasing the annealing temperature decreased the strains in both phases and the specific surface area of the films; but increased the sizes of the pores. At higher annealing temperatures, the transmittance maxima of the films decreased in the visible region and the absorption edges shifted to longer wavelengths. Optical band gap of the films annealed at 300 and 900°C was 3.61 and 3.25eV, respectively. The refractive index of the films increased from 1.71 to 1.92 and their porosity decreased from 63.9 to 49.7% as the annealing temperature increased from 300 to 700°C..

Keywords

Mesoporous TiO2, Thin films, Sol-gel templating technique, structural and optical properties..

Submitted at: June 15, 2010
Accepted at: July 14, 2010

Citation

B. YARMAND, S. K. SADRNEZHAAD, Influence of annealing temperature on structural and optical properties of mesoporous TiO2 thin films prepared by sol-gel templating technique, Journal of Optoelectronics and Advanced Materials Vol. 12, Iss. 7, pp. 1490-1497 (2010)