Zhantao Wei

Transport properties of Bi2Se3 thin films grown by magnetron sputtering

Epitaxial growth of Bi2Se3 thin films is of great current interest due to the advantages in spintronics and thermoelectrical applications. In this paper, Bi2Se3 thin films on Si (111) substrate have been prepared via magnetron sputtering deposition with post-annealing treatment and their microstructures and electrical transport properties were studied. Good quality with highly c-axis oriented films could be obtained after post-annealing treatment. The annealing temperature (Ta) obviously affected the phase structures and electrical properties. The crystallinity and the lattice parameters c of the Bi2Se3 thin-films increased with increasing Ta. The relative atomic ratio of Se/Bi decreased with increasing Ta and large number of Se vacancies was discovered in films with Ta = 350°C. The resistivity of films decreased monotonously and showed weakly metallic resistivity with the increase of Ta. Non-saturated high-field linear magnetoresistance and weak antilocalization were found in films with higher Ta.

Electrical and magnetic transport properties of Co-doped Bi2Se3 topological insulator crystals

Transition metal doped topological insulators (TI) CoxBi2-xSe3 were prepared and the phase structure, electrical and magnetic transport properties, Hall mobility and Hall resistivity were studied. The lattice constant c decreased with the increasing Co concentration. All samples exhibited weak metallic resistivity. With increasing Co concentration, the value of ρxx increased, reaching a maximum at x = 0.02, and then decreased. The resistivity data could be fitted by different formulas below and above 30 K in all samples result from different mechanism corresponding to different temperature regions. The magnetoresistance (MR) of Bi2Se3 TI showed a change dependence of concentration. The MR was enhanced by small quantity of Co doping, attaining a maximum value in Bi1.98Co0.02Se3 crystal; but MR was suppressed in high-doped sample (x > 0.02). Those results were ascribed to the rivalry between the phonon scattering effect and the magnetic ordering in single crystals caused by Co ions. For low-doped samples doped, the contribution of phonon scattering was much higher than that of magnetic ordering, leading to larger MR value. However, in samples doped with higher Co concentrations, the magnetic ordering effect became dominant and caused the MR decreases. The MR increased with decreasing temperature and increasing magnetic field. The Hall mobility data indicated that incorporating Co in Bi2Se3 single crystal can reduce native defect of Bi2Se3.

MAGNETORESISTANCE IN TOPOLOGICAL INSULATOR MnxBi2-xSe3 CRYSTALS

The transport properties of magnetic-atoms doped MnxBi2-xSe3 single crystals are studied. The samples exhibit approximately similar temperature dependence of resistivity behavior under various applied magnetic fields from zero to 9 T. Magnetoresistance (MR) is modified significantly by high concentration of Mn dopants. The scatterings mechanism between the magnetic impurities and electrons plays an important role in both transport properties and MR effect.