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. (C) 2009 Elsevier B.V. All rights reserved.