Electronic processes in bismuth type doped semimetals

Acces full text - https://doi.org/10.1109/SMICND.1995.495047Properties of highly doped bismuth alloys with impurities of the VI group are investigated. Anomalous behaviour of statistical and kinetical characteristics dependence upon the impurity concentration is interpreted within the framework of a notion of impurity states in semimetal systems

Specific Role of Impurities in Semimetals

Access full text – https://doi.org/10.1002/1521-3951(199703)200:13.0.CO;2-VWe have shown that the Fermi energy dependence on temperature in semimetals keeps its well-known form, similar to that of semiconductors, down to T = 0. In the nearest vicinity of T = 0 this dependence is significantly changed, and the Fermi level is displaced toward the top of the valence band. The more different electron and hole effective masses in the model of the overlapped bands in semimetals are, the more sufficient is this displacement. We note the specific role of substitutional impurities in semimetals containing at least two atoms per elementary cell. Of particular interest is the case when an impurity is of donor type when it substitutes an atom in the host elementary cell, and of acceptor type when it substitutes another atom. This phenomenon can be observed experimentally at low temperatures as oscillations of the kinetic coefficients as functions of the impurity concentration, if the energies of the donor and acceptor levels are close to the Fermi energy. We present selected experimental data obtained in Bi, which exhibit these oscillations

Peculiarities of impurity states in bismuth and doping anomaly of some transport phenomena I. Binary alloys

Access full text – https://www.elibrary.ru/item.asp?id=16371251Generalizing data of the most typical peculiarities of influence of the impurities (isovalent (Sb, As), donor (Te, Se) and acceptor (Pb, Sn) ones) on the charge transport phenomena in bismuth are given. Proceedingfrom importance of the application aspect of the problem, in the main the most expressive experimental data and clear physical models are considered in order to avoid using of complex and awkward expressions

Peculiarities of transport properties of thin bismuth wires doped with tin and possibility to increase thermoelectric efficiency of p-branch on their basis

Access full text – https://www.elibrary.ru/item.asp?id=16397846The most typical peculiarities of galvano- and thermomagnetic properties of thin single crystal bismuth wires doped with tin (up to 0.07 at.%) obtained by us the last years are analyzed with the purpose to reveal the ratio of contributions of charge carrier scattering mechanisms in various temperature intervals (2.1-300 K). Influence of degree of actuality of various groups of charge carriers and doping with tin impurities on the power factor value in the region of positive values of the Seebeck coefficient is studied

Optical properties and energetic band structure of Tl3AsS3, Tl3AsSe3 and Tl3SbS3 crystals

Access full text – https://doi.org/10.1016/0921-4526(94)00919-MFundamental absorption edge spectra and reflectivity spectra of TlaAsS3, T13AsSe3 and TlaSbS 3 crystals have been investigated in the range 1-6 eV at 300 and 77 K. Polarization dependences of three excitonic series ground states have been found in TlaAsS 3 and TI3SbS3 crystals. The energetic band structure of these crystals has been built on the basis of experimental reflectivity spectra and theoretical band calculations for crystals of C53v group

Exciton and phonon spectra of acoustooptic Tl3AsS3 crystals

The λ-modulated exciton reflection spectra of Tl3AsS3 crystals are investigated at 8 and 77 K, in which the ground (n=1) and excited (n=2, 3) exciton states are revealed. Taking into account the spatial dispersion, the shapes of λ-modulated reflection spectra of the n=1 line are calculated and the basic parameters of excitons and bands are determined (the translational and reduced masses of excitons and the effective masses of electrons and light and heavy holes). The one-phonon reflection spectra are studied in the region from 50 to 500 cm−1 in polarizations E || c and E ⊥ c. The shapes of one-phonon reflection spectra are calculated and the parameters of vibrational modes E and A2 are determined

The thermopower in bismuth whiskers

Access full text – https://doi.org/10.1002/pssa.2210530107The temperature dependence of the thermopower in Bi whiskers of different thickness (0.3 to 6 μm) is measured within the temperature range 77 to 300 K. At low temperatures the thermopower in the thinnest whiskers changes its sign and becomes positive. Theoretical calculations of the thermopower in Bi whiskers are carried out taking into account the phonon drag effect. Numerical computations prove that the change of sign of the thermopower in thin Bi whiskers at low temperature is caused by phonon drag effect

Quantum interference of surface states in bismuth nanowires probed by the Aharonov-Bohm oscillatory behavior of the magnetoresistance

We report the observation of a dependence of the low temperature resistance of individual single-crystal bismuth nanowires on the Aharonov-Bohm phase of the magnetic flux threading the wire. 55 and 75-nm wires were investigated in magnetic fields of up to 14 T. For 55 nm nanowires, longitudinal magnetoresistance periods of 0.8 and 1.6 T that were observed at magnetic fields over 4 T are assigned to h/2e to h/e magnetic flux modulation. The same modes of oscillation were observed in 75-nm wires. The observed effects are consistent with models of the Bi surface where surface states give rise to a significant population of charge carriers of high effective mass that form a highly conducting tube around the nanowire. In the 55-nm nanowires, the Fermi energy of the surface band is estimated to be 15 meV. An interpretation of the magnetoresistance oscillations in terms of a subband structure in the surface states band due to quantum interference in the tube is presented.Comment: 30 pages, 9 figure

Diameter-dependent thermopower of Bi nanowires

We present a study of electronic transport in individual Bi nanowires of large diameter relative to the Fermi wavelength. Measurements of the resistance and thermopower of intrinsic and Sn-doped Bi wires with various wire diameters, ranging from 150-480 nm, have been carried out over a wide range of temperatures (4-300 K) and magnetic fields (0-14 T). We find that the thermopower of intrinsic Bi wires in this diameter range is positive (type-p) below about 150 K, displaying a peak at around 40 K. In comparison, intrinsic bulk Bi is type-n. Magneto-thermopower effects due to the decrease of surface scattering when the cyclotron diameter is less than the wire diameter are demonstrated. The measurements are interpreted in terms of a model of diffusive thermopower, where the mobility limitations posed by hole-boundary scattering are much less severe than those due to electron-hole scattering.Comment: 32 pages, 12 figures. Previous version replaced to improve readabilit