Dielectric properties of bismuth trioxide thin films

Abstract

A successful method for vacuum evaporation of bismuth trioxide has been developed that produces transparent dielectric films. Films with thicknesses varying from 1000 to 3000 Å have been investigated in a Au-Bi 2O 3-Au thin film capacitor configuration that has a common area of 0.62 cm 2. Shadowed surface replicas and direct transmission electron micrographs of the bismuth trioxide films revealed their surfaces to be extremely smooth and the films to be microcrystalline. Dielectric properties were found to be a function of the fabrication process with relative permittivities ranging from 34.5 to 98.8 and loss tangent values ranging from 0.009 to 0.2. Values of the capacitance per unit area for 1000-Å capacitors ranged from 305 nF/cm 2 to 793 nF/cm 2. Dielectric strength was approximately 8×10 4 V/cm. Studies of relative permittivity and dielectric loss as a function of frequency (50-10,000 Hz) demonstrated the existence of orientational and inter-facial polarization.