Electrical characteristics and preparation of (Ba0.5Sr0.5)TiO3 films by spray pyrolysis and rapid thermal annealing

Functional films of (Ba0.5Sr0.5)TiO3 on Pt (1000 A)/Ti (100 A)/SiO2 (2000 A)/Si substrates are prepared by spray pyrolysis and subsequently rapid thermal annealing. Barium nitrate, strontium nitrate and titanium isopropoxide are used as starting materials with ethylene glycol as solvent. For (Ba0.5Sr0.5)TiO3 functional thin film, thermal characteristics of the precursor powder scratched from as-sprayed films show a remarkable peak around 300-400degC and 57.7% weight loss up to 1000degC. The as-sprayed precursor film with coffee-like color and amorphous-like phase is transformed into the resultant film with white, crystalline perovskite phase and characteristic peaks (110) and (100). The resultant films show correspondent increases of dielectric constant, leakage current and dissipation factor with increasing annealing temperatures. The dielectric constant is 264 and tangent loss is 0.21 in the resultant films annealed at 750degC for 5 min while leakage current density is 1.5x10-6 A/cm2 in the film annealed at 550degC for 5 min. (author)