(Color online) (a) RHEED patterns of an as-grown surface of Bi2Se3 with a thickness of 44 nm. (b) RHEED oscillations of the intensity (upper red) and width (lower blue) of the specular beam. The oscillation period is found to be 68 s, corresponding to a growth rate of ∼0.9 QL/min. (c) Large area AFM image of Bi2Se3 film (size: 0.8 μm × 0.7 μm). (d) The height profile along the gray line marked in Fig. 1(c) showing a step size of 0.95 nm.
(Color online) (a) High-resolution transmission electron microscopy (HRTEM) of a 7 nm Bi2Se3 grown on a Si (111) substrate. The lattice space of (003) plane is 0.955 nm. (b) and (c) the energy dispersive spectroscopy (EDS) of the film and interface, respectively.
(Color online) (a) Core level photoemission and (b) Angle Resolved Photoemission data taken from sample consisting of 44 nm of Bi2Se3 grown on Si(111). (a) Core levels of Se and Bi measured with 100 eV photons. (b) The V-shaped surface state crossing the Fermi level. APRES data were taken using 52 eV photons.
(Color online) (a) Resistivity of four samples with different thicknesses versus temperature. (b) Conductivity vs 1/T. The left (black) dashed line indicates a low temperature activation energy of about 90 meV. The right three (purple) dashed lines indicate an activation of about 37 meV. (c) Conductance versus thickness at T = 20K. The blue dotted line is a parabolic fit. The inset shows σxx versus T −1/4 for the 7 nm think film. Please note that the vertical axis is plotted in log scale. The linear line represents log(σ xx) ∝ T −1/4. (d) Sheet carrier density of a 7 nm thick film as a function of temperature.
(Color online) Magneto-resistance Bi2Se3 thin films for four different thickness at 5 K with low (a) and high magnetic fields (b). (c) MR of a 7 nm film at temperatures from 4 to 10 K. (d) MR with respect to temperature when B = 10 T.
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