Size and temperature dependence of electrical transport properties of vacuum evaporated Bi2Se3 films

Abstract

The Bi2Se3 films of thicknesses in the range 50 to 546 nm are vacuum deposited on glass substrates at room temperature. After annealing for 1 h at 423 K, the electrical resistivity, Hall coefficient, and the thermoelectric power are measured. It is observed that the resistivity is strongly affected by both the film thickness and temperature, and the activation energy (ΔE) is found to vary from 0.116 to 0.279 eV with the decrease in film thickness. The Hall coefficient (RH) as well as the mobility increase with increasing film thickness. Also, the thermoelectric power varies in a similar manner. It is found that the deposits were all of n-type and the carrier concentrations (n) measured by different methods have the order of 1020 cm−3. The analysis combining the data from thermoelectric power and electrical conductivity measurements, by using the effective mean free path theory of size effect in thin films developed by Pichard et al. leads to the determination of mean free path, carrier concentration, Fermi energy, and the parameter Ug = (d ln 1g/d ln E), where Ug is a parameter determining the energy dependence of the mean free path of carriers in infinitely thick films.