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Публікація Size effects and thermoelectric properties of Bi0.98Sb0.02 thin films(Institute of Thermoelectricity National Academy of Sciences of Ukraine, 2020) Rogacheva, E. I.; Novak, K. V.; Orlova, D. S.; Nashchekina, O. N.; Sipatov, A. Yu.; Lisachuk, G. V.The room-temperature dependences of thermoelectric properties (the Seebeck coefficient S, the electrical conductivity σ, the Hall coefficient RH, and the thermoelectric power factor P = S2·σ) on the thickness (d = 5 - 250 nm) of the Bi0.98Sb0.02 solid solution thin films grown on mica substrates by thermal evaporation in vacuum from a single source were obtained. It is shown that the monotonic component of the σ(d) dependence is well described within the framework of the Fuchs-Sondheimer theory for the classical size effect. The presence of an oscillating component in the d-dependences of σ, S, RH and S2·σ is attributed to the manifestation of the quantum size effect, and the experimentally determined period of quantum oscillations Δd = 45 ± 5 nm is in good agreement with the Δd value calculated theoretically within the framework of the model of an infinitely deep potential well. Bibl. 77, Fig. 1.Публікація Thickness-dependent quantum oscillations of the transport properties in bismuth selenide thin films(Elsevier, 2019) Rogacheva, E. I.; Menshikova, S. I.; Sipatov, A. Yu.; Nashchekina, O. N.The objects of the present study were thin n-Bi2Se3 films with thicknesses d = 10–100 nm, grown by thermal evaporation of n-Bi2Se3 crystals in vacuum onto heated glass substrates. The room temperature d-dependences of the Seebeck coefficient, the Hall coefficient, and the electrical conductivity of the films exhibited an oscillatory behavior, which we attribute to quantum size effects. Such interpretation of the results is supported by the fact that experimentally determined values of the oscillation period are in quite good agreement with the theoretically calculated ones. We suggest that the large amplitude and undamped character of the oscillations in the studied range of thicknesses are connected with the topologically protected gapless surface states of Bi2Se3. The observed oscillatory character of the d-dependences of the transport coefficients should be taken into account when 2D-structures are applied in nanothermoelectricity and other fields of nanoscience and nanotechnology.Публікація Structure of thermally evaporated bismuth selenide thin films(Науково-технологічний комплекс "Інститут монокристалів", 2018) Rogacheva, E. I.; Fedorov, A. G.; Krivonogov, S. I.; Mateychenko, P. V.; Dobrotvorskay, M. V.; Garbuz, A. S.; Nashchekina, O. N.; Sipatov, A. Yu.The Bi₂Se₃ thin films with thicknesses d = 7-420 nm were grown by thermal evaporation in vacuum of stoichiometric n-Bi₂Se₃ crystals onto heated glass substrates under optimal technological conditions determined by the authors. The growth mechanism, microstructure, and crystal structure of the prepared thin films were studied using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. It was established that the prepared thin films were polycrystalline, with composition close to the stoichiometric one, did not contain any phases apart from Bi₂Se₃, were of a high structural quality, and the preferential growth direction [001] corresponded to the direction of a trigonal axis C₃ in a hexagonal lattice. The films, like the initial crystal, exhibited n-type conductivity. It was shown that with increasing film thickness, the grain size and the film roughness remain practically the same at thicknesses d < 100 nm, and after that increase, reaching their saturation values at d ~ 300 nm. It follows from the results obtained in this work that using the method of thermal evaporation in vacuum from a single source, one can prepare thin n-Bi₂Se₃ films of a sufficiently high structural quality with a composition close to the stoichiometric one and the preferential growth orientation.Документ Dependences of thermoelectric properties on the thickness of thin films of indium doped lead telluride(Institute of Thermoelectricity, 2014) Menshikova, S. I.; Rogacheva, E. I.; Sipatov, A. Yu.; Matychenko, P. V.; Dobrotvorskaya, M. V.Dependences of thermoelectric properties (the Seebeck coefficient S, the electric conductivity σ, the Hall coefficient RH, the carrier mobilityμ and the thermoelectric power P = S²·σ) on the thickness d (d = 10 – 255 nm) of thin films prepared by vacuum evaporation of indiumdoped PbTe crystals and subsequent condensation on (111) BaF₂ substrates were obtained. With decreasing thickness of films to d ≈ 40 nm, there is n- to p-type inversion of conduction which is related to a change in thermodynamic equilibrium conditions and partial reevaporation of lead and/or indium atoms. Extremes were found on the thickness dependences of properties at d₁ ≈ 20 nm which is indicative of hole gas quantization. In the range of thicknesses with n-type conduction there is a smooth change in thermoelectric properties with thickness which testifies to manifestation of classical size effect and is sufficiently well described in the framework of the Fuchs-Sondheimer theory.Документ Size effects in thin n-PbTe films(STC "Institute for Single Crystals", 2015) Menshikova, S. I.; Rogacheva, E. I.; Sipatov, A. Yu.; Zubarev, Evgeniy N.Документ Size effects in chlorine doped PbSe thin films(Institute of Thermoelectricity, 2015) Menshikova, S. I.; Rogacheva, E. I.; Sipatov, A. Yu.; Krivonogov, S. I.; Matychenko, P. V.The possibility of obtaining strongly degenerate (≈ 3·10²⁰ сm⁻³) PbSe thin films (d = 5 – 220 nm) with n-type conductivity by thermal evaporation in vacuum of PbSe crystals doped with PbCl₂, with subsequent condensation onto (001) KCl substrates was established. It was shown that the films had high homogeneity degree, no grain structure was observed. The thickness dependences of thermoelectric properties (the Seebeck coefficient S, the Hall coefficient RH and the electric conductivity σ) of thin films were obtained. In the thickness range d ≈ 5 ÷ 30 nm, oscillation properties were observed with growth of d that are attributable to electron gas quantization. The calculation of S(d) dependence on the assumption of size quantization with regard to contribution of several subbands and the thickness dependence of the Fermi energy was shown to be in agreement with the experimental data. In the region of d > 30 nm there was growth of S and σ with thickness, which is attributable to manifestation of classical size effect and interpreted in the framework of Fuchs-Sondheimer and Mayer theories.