The Optical Properties and Band Gap Energy of Nanocrystalline La0.4Sr0.6TiO3 Thin Films
The effects of microstructure on the optical properties of La0.4Sr0.6TiO3 thin films were investigated. Dense films with the thickness of ∼200 nm and grain size 14–30 nm were produced on monocrystalline sapphire substrates by using a polymeric precursor spin coating technique at annealing temperatures under 800°C. X-ray data showed the formation of a single-phase cubic perovskite-type structure similar to undoped SrTiO3 for annealing temperatures >500°C. The results of optical measurements showed that the optical spectra varied with the change of the grain size. From these data, the absorption coefficients were calculated and the band gap energy determined. In agreement with the quantum confinement model, it was shown that the band gap energy increased as the grain size decreased.
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Document Type: Research Article
Affiliations: Electronic Materials Applied Research Center, University of Missouri-Rolla, Rolla, Missouri 65401
Publication date: May 1, 2005