Microwave studies of thermally oxidized vacuum evaporated bismuth thin films on alumina

Abstract

The bismuth thin films of various thicknesses (100nm-550nm) were deposited on alumina substrate by vacuum evaporation technique. These films were thermally oxidized in air at three different temperatures (125°C, 150°C, and 175°C). The films were characterized by XRD and SEM. X-ray diffraction studies shows dominant □-Bi2O3 crystal structure. Surface morphology shows granular shaped particles of Bi2O3 on alumina substrate. Microwave properties were studied in the X band (8-12 GHz) using waveguide setup. The Bismuth oxide thin film showed higher microwave transmittance in the 10 to 10.8GHz range and lower reflectance. The dielectric constant and impedance at 12 GHz was measured using waveguide slotted section. The microwave dielectric constant of these Bi2O3 thin films varied from 17 to 46 at 12 GHz and was dependent on thickness and oxidation temperature