Structural and electrical properties of rf-sputtered amorphous barium titanate thin films

Abstract

Structural and electrical properties of rf-sputtered amorphous BaTiO3 thin films grown on water-cooled substrates have been investigated. The dielectric and electrical properties have been studied for films grown under varying sputtering gas composition (Ar+O2 gas mixtures) as a function of film thickness, frequency, and temperature. As-grown films were amorphous in nature and highly transparent. Post-deposition annealing had no discernible effect either on film structure or dielectric properties, and there was no evidence of ferroelectricity. Films sputtered in pure argon showed a dielectric constant ε′∼12 with little dependence on frequency (0.1–100 kHz) over the temperature range 0–75 °C. The dielectric properties were a function of film thickness and the percentage of oxygen in the sputtering gas during growth. The thickness-dependent dielectric properties of amorphous BaTiO3 thin films on conducting glass substrates could be satisfactorily explained by a model based on the existence of electrode barriers. The high breakdown voltage (106 V/cm), charge storage capacity (3.1 μC/cm2), and frequency- and temperature-dependent dielectric properties of a-BaTiO3 films sputtered in pure argon show promise for application as insulating layers in thin-film electroluminescent display devices.