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In anisotropic layered films of a multicomponent n-Bi1.92In0.02Te2.85Se0.15 solid solution in strong magnetic fields from 2 to 14 T at low temperatures, quantum oscillations of the magnetoresistance associated with the surface states of electrons in three-dimensional topological insulators are studied. From analysis of the spectral distribution of the amplitudes of quantum magnetoresistance oscillations, the main parameters of the Dirac-fermion surface states are determined. The results are compared with data obtained by the method of scanning tunneling spectroscopy. It is shown that a high surface concentration determines the contribution of the Dirac-fermion surface states to the thermoelectric properties of n-Bi1.92In0.02Te2.85Se0.15 films. [ABSTRACT FROM AUTHOR]

The surface states of Dirac fermions in p-Bi2Te3, p-Bi2 –xSbxTe3 –ySey, and p-Bi2 –x–ySnxGeyTe3 thermoelectrics were studied and its topological characteristics were obtained by scanning tunneling techniques in dependence on compositions. It was shown that the thermoelectric power factor and the material parameter enhance with the shift of the Dirac point to the top of the valence band with the increasing of atomic substitution in these thermoelectrics. A growth contribution of the surface states is determined by an increase of the Fermi velocity for large atomic substitutions of Bi at x > 1.5 and small substitutions in the Te sublattice (y = 0.06). In compositions with smaller substitutions at x = 1–1.3 and y = 0.06–0.09, similar effect of the surface states is determined due to raising the surface concentration of charge carriers. [ABSTRACT FROM AUTHOR]

In n-Bi2Te3 and n-Bi2Te3 –ySey thermoelectrics, the surface states of Dirac fermions of the interlayer Van der Waals surface (0001) are studied by scanning tunneling microscopy and spectroscopy. The surface morphology and modulated line profiles of the tunneling microscopy images are determined by local distortions of the surface density of electronic states and depend on the composition. The Dirac point ED in the studied compositions is localized in the band gap and shifts to the top of the valence band with increasing Se content in n-Bi2Te3 –ySey alloys. The dependence between the parameters of the surface states of Dirac fermions (Dirac-point position, Fermi velocity, surface fermion concentration) and thermoelectric properties (Seebeck coefficient and power parameter) in the thermoelectrics under study is determined. [ABSTRACT FROM AUTHOR]

The thermoelectric properties in the temperature range 4.2–300 K and magnetoresistance oscillations in strong magnetic fields at low temperatures are studied in nanostructured layered films of topological thermoelectric materials n-Bi2 –xSbxTe3 –ySey. It is shown that the thermoelectric figure of merit in layered n-Bi2 –xSbxTe3 –ySey films is larger than that in the bulk material due both to an increase in the Seebeck coefficient below room temperature and to a decrease in the thermal conductivity and its weaker temperature dependence. Analysis of the magnetoresistance oscillations is used to determine the parameters of the topological surface states of Dirac fermions and estimate their influence on the thermoelectric properties. [ABSTRACT FROM AUTHOR]