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Abstract: Single crystals of Sb2− x Fe x Te3 (c Fe=0–9.5×1019 cm−3) were prepared by Bridgman method. The interpretation of the reflection spectra in plasma resonance region indicates that Fe increases the concentration of holes (acceptor) and each Fe atom incorporated in Sb2Te3 structure liberates 0.4–0.5 hole. Observed effect is elucidated by means of point defect model. According to the model Fe atoms enter the structure and form uncharged substitutional defects . Since this defect cannot affect the free-carrier concentration directly, we assume an interaction of the entering Fe-atoms with natives defects leading to a rise in the concentration of antisite defects , to a decrease of concentration, and to an increase in the concentration of holes. [Copyright &y& Elsevier]

Detailed transport studies of single crystals of Bi2Se3 were made in the temperature range of 2–300 K, and the data were analyzed in terms of a model consisting of two groups of electrons—a centrosymmetrical lower conduction band and an upper conduction band located away from the Γ-point. Very good agreement with the experimental data is obtained assuming the electrons are scattered on acoustic phonons and ionized impurities. A rather strong influence of the latter mechanism is attributed to a large number of charged selenium vacancies in Bi2Se3. The fitted transport parameters were used to calculate the electronic portion of the thermal conductivity that, in turn, allowed for the determination of the lattice thermal conductivity. The Debye model provides a good approximation to the temperature dependence of the lattice thermal conductivity. [Copyright &y& Elsevier]

From IR reflectivity spectra measurement on natural (0001) cleavage planes of Bi2−xSbxSe3 single crystals (space group D53d–R3m), values of plasma resonance frequency ωp were determined. Using the model respecting the existence of light and heavy electrons the dependence of free current carriers concentration on Sb-atom content in Bi2−xSbxSe3 single crystals (for x=0.0 – 0.4) was obtained. There is a maximum in this dependence at lower Sb concentration (x ≅ 0.024). This effect is explained by a model of point defects, where both the concentration of negatively charged native defects in a Bi2Se3 lattice (anti-site defect Bi′Se, “seven-layer lamellae” Bi3Se−4) and the concentration of vacancies in a selenium sublattice (V••Se) decreases with Sb content. On this basis the observed rise of the Hall mobility RHσ in the range from 500 to 1200 cm2/Vs is explained. [Copyright &y& Elsevier]

Abstract: Insertion/extraction of lithium ions into/from Bi2Se3 crystals was investigated by means of cyclic voltammetry. The process of insertion is reflected in the appearance of two bands on voltammograms at ∼1.7 and ∼1.5V, corresponding to the insertion of Li+ ions into octahedral and tetrahedral sites of the van der Waals gap of these layered crystals. The process of extraction of Li+ ions from the gap results in the appearance of four bands on the voltammograms. The bands 1 and 2 at ∼2.1 and ∼2.3V correspond to the extraction of a part of Li+ guest ions from the octahedral and tetrahedrals sites and this extraction has a character of a reversible intercalation/deintercalation process. A part of Li+ ions is bound firmly in the crystal due to the formation of negatively charged clusters of the (LiBiSe2.Bi3Se4 −) type. A further extraction of Li+ ions from the van der Waals gap is associated with the presence of bands 3 and 4 placed at ∼2.5 and ∼2.7V on the voltammograms as their extraction needs higher voltage due to the influence of negative charges localized on these clusters. [ABSTRACT FROM AUTHOR]