Dielectric properties of sol-gel derived barium-strontium-titanate (Ba/sub 0.4/Sr/sub 0.6/TiO/sub 3/) thin films

The structural and dielectric properties of sol-gel derived barium-strontium-titanate (Ba/sub 0.4/Sr/sub 0.6/TiO/sub 3/) thin films have been investigated. The as-fired films are found to be amorphous, and films crystallize to a cubic phase after a post deposition annealing at 700/spl deg/C for one hour in air. The variation of dielectric constant with temperature and field was investigated as a function of film thickness. These films display a nonlinear dielectric response that can be described in terms of a power series expansion of the free energy in polarization as in Landau-Ginzburg-Devonshire approach. The measured room temperature dielectric constant (/spl epsi/') of the film was about 320. The dielectric constant did not show any significant frequency dependence up to 100 kHz. The temperature dependence of dielectric constant exhibited a diffused ferroelectric to paraelectric phase transition at -60/spl deg/C. The room temperature dielectric constant and magnitude of the dielectric peak at the Curie point was dependent on the thickness of the film. The obtained dielectric data on sol-gel barium strontium titanate thin films on platinized substrates were analyzed in the light of a barrier layer model.