Issue Eur. Phys. J. Appl. Phys. Volume 45, Number 3, March 2009 Article Number 30602 Number of page(s) 8 Section Nanomaterials and Nanotechnologies DOI 10.1051/epjap/2009010 Published online 17 February 2009

Eur. Phys. J. Appl. Phys. 45, 30602 (2009)
DOI: 10.1051/epjap/2009010

Effect of crystallization on optical properties of sol-gel processed nano-sized strontium titanate (SrTiO₃) thin films

S.B. Singh and H.B. Sharma

Department of Physics, Manipur University, 795003 Imphal, India

bsoram@rediffmail.com

Received: 29 June 2008 / Accepted: 16 December 2008 / Published online: 17 February 2009

Abstract
Strontium titanate (SrTiO₃) or ST thin films have been prepared using strontium 2-ethylhexanoate [Sr[CH₃(CH₂)₃CH(C₂H₅)CO₂]₂] and titanium(IV) isopropoxide Ti[OCH(CH₃)₂]₄ as precursors using a modified sol-gel processing technique. The precursor [Sr[CH₃(CH₂)₃CH(C₂H₅)CO₂]₂] was synthesised in the laboratory. Transparent and crack-free films were fabricated on pre-cleaned quartz substrates by spin coating. The structural and optical properties of films annealed at different temperatures have been investigated. The as-fired film was found to be amorphous while crystalline, cubical phase structure film was obtained after annealing at 550 °C for one hour in air. The films are polycrystalline in structure with the lattice constants of a = 3.90 Å. The grain sizes of the films annealed at 450, 500 and 550 °C were found to be 26.4, 31.8 and 35.2 nm, respectively. The optical constants of the films (refractive index, extinction coefficient, optical conductivity, complex dielectric constant, and energy band gap) were determined from the transmittance spectra. The refractive indexes of the films were found to increase while the optical band gaps were found to decrease with annealing temperature. The optical dispersion data are also analysed in the light of single oscillator model and are discussed.

PACS
77.80.-e - Ferroelectricity and antiferroelectricity.
68.55.-a - Thin film structure and morphology.
78.20.-e - Optical properties of bulk materials and thin films.
78.20.ci - Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity).

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