Thickness dependences of the thermoelectric properties of Bi thin films

Bismuth films with thicknesses d=(3-300) nm were fabricated by thermal evaporation in vacuum and subsequent deposition on mica substrates at temperatures of 300 K and 373 K. Electron microscopy and electron diffraction studies showed that the films grow on substrates in an island-like fashion. With increasing substrate temperature, the formation of a continuous film occurs at larger d values, while the degree of the film structural perfection increases. The electrical conductivity, thermoelectric power, Hall coefficient, charge carrier mobility, and power factor of Bi thin films were determined at room temperature, and isotherms of the thermoelectric properties are plotted. It was established that the d-dependences of these properties for Bi thin films obtained on substrates at a temperature of 373 K, exhibit a distinctly oscillatory behavior, which is attributed to the manifestation of quantum size effects. The influence of various factors, such as the substrate temperature, film aging, and oxidation, on the behavior of the d-dependences of the thermoelectric properties was studied.