Characterization of doped BST thin films prepared by a modified sol gel method

Abstract

Barium strontium titanate (BST) films have been fabricated using a modified sol gel method. The crystallization temperature was 100°C higher than that for lead zirconate titanate. The electrical properties improved when multiple rapid thermal processing was used. The dielectric constant of BST films was of the order of 250 which was characteristic of a small grain size and the presence of a low dielectric constant barrier. Doping by La, Nb, Mg, Y, Ru, Mn and Gd had an adverse effect on the dielectric constant even for small concentrations of about 1 at.%. Doping with cerium up to 3 at.% increased the dielectric constant of BST films up to 300 while dielectric losses remained low ≈ 0.025. The leakage current densities improved for donor type doping and were < 10 nA/cm² at E=60 kV/cm. BST films 1900 Å thick doped with 3 at.% of Ce had a charge storage density and capacitance density of 50 fC/μm² and 15 fF/μm² respectively.