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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 Growth and structure of thermally evaporated Bi2Te3 thin films(Elsevier, 2016) Rogacheva, E. I.; Budnik, A. V.; Dobrotvorskaya, M. V.; Fedorov, A. G.; Krivonogov, S. I.; Mateychenko, P. V.; Nashchekina, O. N.; Sipatov, A. Yu.The growth mechanism, microstructure, and crystal structure of the polycrystalline nBi2Te3 thin films with thicknesses d = 15 – 350 nm, prepared by thermal evaporation in vacuum onto glass substrates, were studied. Bismuth telluride with Te excess was used as the initial material for the thin film preparation. The thin film characterization was performed using X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, scan electron microscopy, and electron force microscopy. It was established that the chemical composition of the prepared films corresponded rather well to the starting material composition and the films did not contain any phases apart from Bi2Te3. It was shown that the grain size and the film roughness increased with increasing film thickness. The preferential growth direction changed from [00l] to [015] under increasing d. The X-ray photoelectron spectroscopy studies showed that the thickness of the oxidized surface layer did not exceed 1.5 – 2.0 nm and practically did not change in the process of aging at room temperature, which is in agreement with the results reported earlier for single crystals. The obtained data show that using simple and inexpensive method of thermal evaporation in vacuum and appropriate technological parameters, one can grow n-Bi2Te3 thin films of a sufficiently high quality.Документ Структура тонких пленок p-Bi₂Se₃, полученных термическим испарением в вакууме из одного источника(Інститут термоелектрики НАН України, 2015) Рогачева, Елена Ивановна; Будник, А. В.; Федоров, А. Г.; Кривоногов, С. И.; Матейченко, П. В.С использованием методов рентгеновской дифрактометрии, сканирующей электронной микроскопии, энергодисперсионной спектрометрии и атомной силовой микроскопии исследованы механизм роста, микроструктура и кристаллическая структура тонких пленок Bi₂Te₃ с толщинами d = 28-620 нм, полученных термическим испарением в вакууме кристаллов Bi₂Te₃ стехиометрического состава на стеклянные подложки. Полученные тонкие пленки были поликристаллическими, обладали р-типом проводимости и не содержали других фаз, кроме Bi₂Te₃. Показано, что с увеличением толщины пленок размер кристаллитов увеличивается до ~ 700-800 нм. Установлено, что преобладающим направлением роста кристаллитов является направление [00l], соответствующее направлению тригональной оси С₃ в гексагональной решетке. С увеличением толщины пленок свыше ~ 200-250 нм наряду с отражениями от плоскостей (00l) появляются отражения от других плоскостей, свидетельствующие о некоторой разориентации кристаллитов. Полученные результаты показывают, что, используя простой и недорогой метод термического испарения из одного источника и оптимальные технологические параметры, можно получить тонкие пленки p-Bi₂Te₃ достаточно высокого качества.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 Structure of p-Bi₂Te₃ thin films prepared by single source thermal evaporation in vacuum(2015) Rogacheva, E. I.; Budnik, A. V.; Fedorov, A. G.; Krivonogov, A. S.; Mateychenko, P. V.The growth mechanism, microstructure, and crystal structure of thin Bi₂Te₃ films with thicknesses d = 28 - 620 nm prepared by thermal evaporation of stoichiometric Bi₂Te₃ crystals in vacuum onto glass substrates were studied using X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and atomic force microscopy. The obtained thin films were polycrystalline, exhibited p-type conductivity and did not contain any other phases except for Bi₂Te₃. It was shown that with increasing film thickness, the crystallite size increased up to ~ 700-800 nm. It was established that the preferential orientation of crystallite growth was [00l] direction corresponding to a trigonal axis С3 in hexagonal lattice. When the film thickness exceeded ~ 200-250 nm, along with reflections from (00l) planes, reflections from other planes appeared, which indicated a certain disorientation of crystallites. The results obtained show that using a simple and inexpensive method of thermal evaporation from a single source and choosing optimal technological parameters, one can grow thin p-Bi₂Te₃ films of sufficiently high quality.