Перегляд за Автор "Doroshenko, A. N."
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Документ Concentration dependences of galvanomagnetic and thermoelectric properties of Bi1-xSbx thin films in the range x = 0 – 0.25(Національна академія наук України, 2019) Rogacheva, E. I.; Doroshenko, A. N.; Sipatov, A. Yu.; Nashchekina, O. N.Документ Dependence of minority charge carriers lifetime on point defects type and their concentration in single-crystal silicon(Scientific and Technological Corporation "Institute for Single Crystals", 2011) Zaitsev, R. V.; Kirichenko, M. V.; Doroshenko, A. N.; Khrypunov, G. S.Using the computer simulation method it was studied the dependences of nonequili-brium electrons lifetime from concentration of elementary bulk point defects and various complexes of the bulk point defects, which may be present in the diode structures based on p-type conductivity boron doped silicon crystals with 10 Ohm-cm resistivity, grown by the Czochralski method. A number of obtained results well correlated with the experimental data related to the effects of photon degradation in solar cells which based on considered type silicon crystals (Si-SC) and influence of a stationary magnetic field on such devices efficiency. Overall, our results provide additional possibility for the evolution features prediction of electronic, and consequently, functional parameters, not only for Si-SC, but also for other devices based on such diode structures. It will allow looking for the most efficient and cost effective ways to optimize their design-technological solutions, and also estimates their reliability and durability level.Документ Effect of aging on thermoelectric properties of the Bi2Te3 polycrystals and thin films(Науково-технологічний комплекс "Інститут монокристалів", 2021) Rogacheva, E. I.; Doroshenko, A. N.; Novak, K. V.; Sipatov, A. Yu.; Khramova, T. I.; Saenko, S. A.The temperature dependences (77-300 K) of the thermoelectric (TE) properties (the Seebeck coefficient S, electrical conductivity σ, Hall coefficient RH, Hall charge mobility μH>, and TE power factor P) were studied for freshly prepared and for exposed to air at room temperature during 5 years p-Bi2Te3 (60.0 at.% Te) and n-Bi2Te3 (62.8 at.% Te) polycrystals and thin films grown from them by thermal evaporation in vacuum. It was found that after aging, in the p- and n-Bi2Te3 bulk crystals and in the n-type film obtained from the n-Bi2Te3 crystal, type of conductivity is reserved but the p-type film obtained from the p-Bi2Te3 crystal, change the type of conductivity from hole to electronic. The activation energies of possible defect states were determined using the RH(T) dependences. After aging, at the temperatures close to room temperature, the p values of n-Bi2Te3 and p-Bi2Te3 polycrystals decreases by ~ 20 %, but p values of the n-type film grown from n-Bi2Te3 crystal increases by 20-30 %. In the p-type film obtained from p-Bi2Te3 polycrystal, and having changed the type of conductivity after aging, the p values exceed the p values of a film obtained from n-Bi2Te3 polycrystal by ~ 35 % at 250 K and by 25 % at 300 K, remaining at these temperatures below the p values for n-Bi2Te3 polycrystal after aging by ~ 15 %.Документ Effect of Bi on Mechanical and Transport Properties of Antimony(Прикарпатський національний університет імені Василя Стефаника, 2019) Rogacheva, E. I.; Doroshenko, A. N.; Khramova, T. I.; Men'shov, Yu. V.Документ Effect of Deviation from Stoichiometry on Thermoelectric Properties of Bi₂Te₃ Polycrystals and Thin Films in the Temperature Range 77-300 K(Сумський державний університет, 2019) Rogacheva, E. I.; Novak, K. V.; Doroshenko, A. N.; Nashchekina, O. N.; Budnik, A. V.Bi₂Te₃ semiconductor compound and Bi₂Te₃-based solid solutions are presently among the best lowtemperature thermoelectric materials. One of the methods of controlling the conductivity type and properties of Bi₂Te₃ is changing the stoichiometry of this compound. Earlier, we have obtained the room-temperature dependences of mechanical and thermoelectric properties of Bi₂Te₃ polycrystals on the degree of deviation from stoichiometry. The goal of this work is to investigate the behavior of such dependences at other temperatures. Bismuth telluride polycrystals with compositions in the range of 59.6-67.5 at. % Te were obtained, and for all the crystals the Seebeck coefficient, the Hall coefficient, electrical conductivity and charge carrier mobility were measured in the temperature range 77-300 K. On the basis of the temperature dependences, the isotherms of kinetic coefficients were plotted. It was found that similar to the room-temperature isotherms, the isotherms at lower temperatures were non-monotonic: they exhibited inversion of the conductivity sign between 60.5 and 61.0 at. % Te and extrema near 60.0 and 63.0 at. % Te. The experimental data are interpreted taking into account changes in the band and defect structures of Bi₂Te₃ under varying stoichiometry. The obtained results make it possible to control thermoelectric properties of Bi₂Te₃ polycrystals in the temperature range 77-300 K by changing the degree of deviation from stoichiometry.Документ Electronic phase transitions in thin films of Bi1-xSbx solid solutions(Grupo Pacifico, 2018) Rogacheva, E. I.; Doroshenko, A. N.; Nashchekina, O. N.Документ Galvanomagnetic properties of polycrystalline Bi₁₋ₓSbₓ solid solutions in the concentration range x = 0-0.25(Науково-технологічний комплекс "Інститут монокристалів", 2020) Rogacheva, E. I.; Doroshenko, A. N.; Drozdova, A. A.; Nashchekina, O. N.; Men'shov, Yu. V.The dependences of the Hall coefficient, electrical conductivity, magnetoresistance, electron and hole concentration and mobility on the Bi₁₋ₓSbₓ solid solution composition in the concentration range x = 0-0.25 at 77 and 300 K in magnetic fields 1 T and 0.05 T were obtained. It was shown that all the dependences exhibit a distinct nonmonotonic oscillating behavior at both temperatures and in both magnetic fields. The presence of concentration-dependent anomalies of galvanomagnetic properties is attributed to critical phenomena accompanying the percolation-type transition from dilute to concentrated solid solutions and electronic phase transitions: a transition to a gapless state, the semimetal – semiconductor transition, and indirect – direct band gap semiconductor transition.Документ Influence of Composition on the Thermoelectric Properties of Bi1-xSbx Thin Films(IOP Publishing Ltd, 2016) Rogacheva, E. I.; Nashchekina, O. N.; Doroshenko, A. N.; Sipatov, A. Yu.; Dresselhaus, M. S.Документ Magnetoresistance of Polycrystalline Bi₁₋ₓSbₓ Alloys (x = 0 – 0.07)(IEEE, 2017) Doroshenko, A. N.; Martynova, K. V.; Rogacheva, E. I.A detailed investigation of the composition dependences of magnetoresistance for polycrystalline Bi₁₋ₓSbₓ solid solutions in a concentration range x = 0 – 0.07 was performed at 300 K in weak and strong magnetic field. It was shown that the composition dependences of magnetoresistance are clearly expressed nonmonotonic type. The presence of concentration anomalies of magnetoresistance was confirmed that had been earlier observed in the range x = 0 – 0.1 on cast samples after different kinds of thermal treatment and interpreted as a manifestation of electron phase transitions. It is shown that the position of the extrema does not depend on the magnitude of the magnetic field in the interval 0.01 - 1.0 T.Документ Percolation effects and self-organization processes in Bi₂(Te₁₋ₓSeₓ)₃ solid solutions(Easy Conferences Ltd, 2019) Rogacheva, E. I.; Shelest, T. N.; Martynova, E. V.; Doroshenko, A. N.; Nashchekina, O. N.Документ Percolation effects and self-organization processes in Bi₂(Te₁₋ₓSeₓ)₃ solid solutions(Науково-технологічний комплекс "Інститут монокристалів", 2019) Rogacheva, E. I.; Shelest, T. N.; Martynova, E. V.; Doroshenko, A. N.; Nashchekina, O. N.; Men'shov, Yu. V.The room-temperature dependences of microhardness H, electrical conductivity σ, the Seebeck coefficient S, and thermoelectric power factor P on composition of Bi₂(Te₁₋ₓSeₓ)₃ solid solutions were measured in the concentration range x = 0 - 0.07. In the intervals x = 0.0075 - 0.0175 and x = 0.025 - 0.035, an anomalous decrease in H and S and increase in σ with increasing x were observed. The first concentration-dependent anomaly was attributed to critical phenomena, accompanying a percolation-type phase transition. The percolation threshold xc and the radius of deformation spheres R₀ around Se impurity atoms were estimated. The second anomaly is assumed to be connected with a short-range ordering in the solid solution. The non-monotonic character of the dependences of H on the load on an indenter, whose behavior depended on the impurity concentration, was attributed to the interaction of the deformation fields created by dislocations and impurity atoms.Документ Percolation effects and self-organization processes in cold-pressed Bi2(Te1−xSex)3 solid solutions(Elsevier Ltd, 2021) Rogacheva, E. I.; Martynova, E. V.; Shelest, T. N.; Doroshenko, A. N.; Nashchekina, O. N.It was established that the dependences of thermoelectric and mechanical properties of cold-pressed Bi2(Te1−xSex)3 alloys on composition (x = 0–0.07) exhibit a non-monotonic behavior in certain concentration ranges: an anomalous decrease in the Seebeck coefficient, thermoelectric power factor, and microhardness, and increase in electrical conductivity with increasing x. We observed similar anomalies earlier for cast Bi2(Te1−xSex)3 alloys and explained them by percolation and self-organization phenomena. Thus, the existence of the anomalies does not depend on the method of sample preparation. However, in pressed samples as compared to cast ones conductivity type changes from p to n and thermoelectric power factor increases.Документ Percolation transition and physical properties of Bi1-xSbx solid solutions at low Bi concentration(Elsevier Ltd, 2020) Rogacheva, E. I.; Doroshenko, A. N.; Khramova, T. I.; Nashchekina, O. N.; Fedorov, A. G.; Mateychenko, P. V.The dependences of microhardness H, electrical conductivity σ, charge carrier mobility μH, the Seebeck coefficient S, and thermoelectric power factor P = S2σ on the composition of Bi1-xSbx solid solutions in the vicinity of pure Sb (x = 1.0–0.975) were obtained. In the range of x = 0.9925–0.9875, an anomalous decrease in H and S and increase in σ and μH with increasing Bi concentration were observed. For all the alloys, the dependences of H on the load on an indenter G were plotted. It was found that the H(G) dependences for samples with x smaller than ~ 0.99 and for samples with x exceeding 0.99, exhibit different behavior. The results obtained are interpreted on the basis of our assumption about the existence of a percolation-type phase transition from impurity discontinuum to impurity continuum that occurs in any solid solution.Документ Temperature and concentration dependences of specific heat of Bi₁₋ₓSbₓ solid solutions(Науково-технологічний комплекс "Інститут монокристалів", 2018) Rogacheva, E. I.; Doroshenko, A. N.; Nashchekina, O. N.For Bi₁₋ₓSbₓ solid solutions, the concentration (x = 0 - 0.12) and temperature (170-525 K) dependences of specific heat Cp were obtained. At all temperatures studied, three peaks of Cp were observed near x = 0.015, x = 0.037, and x = 0.07. The observed effects were attributed to critical phenomena accompanying the second-order phase transitions: percolation transition from dilute to concentrated solid solutions, the transition to a gapless state, and the semimetal-semiconductor transition, respectively. It was shown that the values of critical indexes (α = 0.11 ± 0.01) are the same not only for different peaks but also for different temperatures and correspond to the values theoretically calculated within the framework of scale-invariant theory for three-dimensional (3D) models.Документ Temperature and magnetic field dependences of thermoelectric properties of Bi1-xSbx solid solutions in the range x = 0 – 0.25(Easy Conferences Ltd, 2019) Rogacheva, E. I.; Doroshenko, A. N.; Nashchekina, O. N.Документ Temperature and magnetic field dependences of thermoelectric properties of Bi1-xSbx solid solutions in the range x = 0-0.25(Elsevier Ltd, 2021) Rogacheva, E. I.; Doroshenko, A. N.; Nashchekina, O. N.Bi1–xSbx solid solutions are the best n-type thermoelectric materials for use at temperatures ≤200 K. An important parameter determining material’s figure of merit is charge carrier concentration. To determine it correctly, one should carry out measurements in a weak magnetic field. On the basis of the magnetic field dependences of the Hall coefficient and magnetoresistance, the dependences of the weak magnetic field boundary Bc on composition (x = 0–0.25) and temperature (T = 77–300 K) for polycrystalline Bi1–xSbx alloys were plotted. It was established that the Bc(x) dependences exhibit a non-monotonic behavior which is attributed to the existence of electronic phase transitions.Документ Thermoelectric properties of polycrystalline Bi₁₋ₓSbₓ solid solutions in the concentration range x = 0 – 0.25(National Academy of Sciences of Ukraine, 2016) Doroshenko, A. N.; Rogacheva, E. I.; Drozdova, А. А.; Martynova, K. V.; Men'shov, Yu. V.A detailed investigation of the dependence of thermoelectric properties of polycrystalline Bi₁₋ₓSbₓ solid solutions on composition in a wide concentration range (x = 0 – 0.25) was performed at room temperature. The objects of study were cast samples of various composition obtained by ampoule method in one technological cycle consisting in cooling of ampoules with melts in the air and subsequent long homogenizing annealing at temperature (520 ± 5) K for 720 hours. It was shown that the composition dependences of properties are of clearly expressed nonmonotonic type. The presence of concentration anomalies of thermoelectric properties was confirmed that had been earlier observed in the range x = 0 – 0.1 on cast samples after different kinds of thermal treatment and interpreted as manifestation of electron phase transitions. A complicated nature of dependences at x > 0.1 is attributable to qualitative changes in Bi₁₋ₓSbₓ band structure at certain critical compositions, a change in relative contribution to conductivity of charge carriers from different energy bands with a change in antimony concentration and high sensitivity of energy spectrum and physical properties of Bi₁₋ₓSbₓ к to external effects.Документ Transport properties of the bismuth telluride thin films with different stoichiometry in the temperature range 77-300 K(Науково-технологічний комплекс "Інститут монокристалів", 2020) Rogacheva, E. I.; Novak, K. V.; Doroshenko, A. N.; Nashchekina, O. N.; Budnik, A. V.The objects of the present study are thin films with thicknesses d = 45-620 nm prepared by thermal evaporation in vacuum from a single source, using undoped p- and n-type Bi₂Te₃ polycrystals with different stoichiometry (60.0 and 62.8 at. % Te, respectively) as a charge, and subsequent condensation on glass substrates at 500 K. The temperature dependences of the Hall coefficient Rн, electrical conductivity σ, and Hall charge carrier mobility μн of thin films were obtained in the range 77-300 K. It was found that the films had the same type of conductivity as the initial polycrystals in the entire temperature range studied and, like in the initial crystals, σ and μн decreased with increasing temperature. The exponents ν in the μн(T) dependences for the bulk polycrystals were larger than those for the films and increased with increasing d. In contrast to the p-type bulk polycrystals, Rн of the p-type films decreased under increasing temperature. In the n-type Bi₂Te₃, Rн decreased with temperature for both thin films and bulk crystals, however, the character of the Rн(T) dependences for the crystals and films differed. The decrease in Rн with temperature before the range of intrinsic conductivity in all thin films is attributed to the existence of donor and acceptor defect states.