Structural and magnetotransport properties of Bi thin films grown by thermal evaporation

We report the structural and magnetotransport properties of three 300-nm-thick Bi thin films grown on Si (0 0 1) substrates by means of thermal evaporation using different buffer layer (175-nm-thick Si3N4, highly resistive Si and 800-nm-thick SiO2, respectively). X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicate that the Bi films are polycrystalline with the grains preferentially oriented along the trigonal-axis [0 0 1]. The Bi film evaporated on SiO2 presents the highest crystallinity which reflects on a higher magnetoresistance value (120% at room temperature and 160% at 2 K and 90 kOe), whereas the lowest magnetoresistance value is found for the Bi film evaporated on Si3N4 (90% at room temperature and 140% at 2 K and 90 kOe). The magnetic field dependence of the Hall resistivity indicates the presence of both electrons and holes whose contributions strongly depend on the temperature. As a function of temperature, a significant enhancement of the hall resistivity is found below 150 K. Interestingly, the MR values show an enhancement at the same temperature, which indicates changes in the carrier densities and mobilities below 150 K.