Optical and electrical properties of thermally oxidized bismuth thin films

Bismuth trioxide (Bi2O3) thin films were prepared by dry thermal oxidation of metallic bismuth films deposited by vacuum evaporation. The oxidation process of Bi films consists of a heating from the room temperature to an oxidation temperature (To = 673 K), with a temperature rate of 8 K/min; an annealing for 1 h at oxidation temperature and, finally, a cooling to room temperature. The optical transmission and reflection spectra of the films were studied in spectral domains ranged between 300 nm and 1700 nm, for the transmission coefficient, and between 380 nm and 1050 nm for the reflection coefficient, respectively. The thin-film surface structures of the metal/oxide/metal type were used for the study of the static current-voltage (I-U) characteristics. The temperature of the substrate during bismuth deposition strongly influences both the optical and the electrical properties of the oxidized films. For lower values of intensity of electric field (ξ < 5 × 104V/cm), I-U characteristics are ohmic.

► Thermally oxidized bismuth thin films have polycrystalline and multiphase structure. ► The optical properties of bismuth trioxide thin films are sensitive to substrate temperature. ► The electrical measurements I = I(U) for all investigated films show that Ohm's law is obeyed.