Dielectric properties of sol-gel derived barium-strontium-titanate(Ba0.4Sr0.6TiO3) thin films

摘要

The structural and dielectric properties of sol-gel derivednbarium-strontium-titanate (Ba0.4Sr0.6TiO3n) thin films have been investigated. The as-fired films are foundnto be amorphous, and films crystallize to a cubic phase after a postndeposition annealing at 700°C for one hour in air. The variation ofndielectric constant with temperature and field was investigated as anfunction of film thickness. These films display a nonlinear dielectricnresponse that can be described in terms of a power series expansion ofnthe free energy in polarization as in Landau-Ginzburg-Devonshirenapproach. The measured room temperature dielectric constant (ε') ofnthe film was about 320. The dielectric constant did not show anynsignificant frequency dependence up to 100 kHz. The temperaturendependence of dielectric constant exhibited a diffused ferroelectric tonparaelectric phase transition at -60°C. The room temperaturendielectric constant and magnitude of the dielectric peak at the Curienpoint was dependent on the thickness of the film. The obtainedndielectric data on sol-gel barium strontium titanate thin films onnplatinized substrates were analyzed in the light of a barrier layernmodel