Al1-xSix films were obtained by ion beam sputtering of an Al-Si composite target. Studies of the structure and electronic structure of Al1-xSix films were carried out. The structure and electronic structure of the films were investigated. The formation of an ordered phase of Al3Si was detected using X-ray diffraction and X-ray emission spectroscopy, as well as theoretical calculation of the band structure and Si L2.3-, Al L2.3-spectra. It is established that the Al3Si phase has a Cu3Au (Pm3m) type structure with a lattice parameter a=4.085 angstrom, the primitive sublattices of which are filled with atoms of two types Al and Si. It was found that the long-range order in Al1-xSix ion-beam films is sufficiently resistant to changes in the elemental composition from Al0.75Si0.25 to Al0.55Si0.45.

Problems of the growth of nanoscale columnar AlxGa1-xN/AlN heterostructures on hybrid substrates involving porous silicon and silicon carbide layers by molecular beam epitaxy technique with plasma-activated nitrogen are discussed in this study. The epitaxial growth of nanoscale columnar AlxGa1-xN/AlN heterostructure is shown to be specified by the layer of silicon carbide, which is formed by atomic substitution technique, and a porous silicon sublayer predetermines the oriented growth of SiC. The performed complex of structural-spectroscopic analysis demonstrated that epitaxial growth of the nuclear AlN layer on all types of the substrates in N-enriched conditions resulted in the formation of AlxGa1-xN/AlN heterostructures with Ga-polar surface. At the same time it was found that the layer of ordered AlxGa1-xN alloy was formed only on the hybrid SiC/porSi/cSi substrate. The layer of AlxGa1-xN on the substrates of cSi and porSi/cSi is present in the state of disordered alloy with an excess content of gallium atoms. Nanocolumns of AlxGa1-xN/AlN grown on the hybrid SiC/porSi/cSi substrate have two types of preferential azimuthal orientation that affects not only their structural and optical properties but also the value of elastic deformation in the heterostructure nanoscale layers. For the first time, azimuthal dependence of intensity of E1(TO) and E2high photon modes was detected in the Raman spectra. The observed periodicity angle in micro-Raman scattering coincides with the characteristic swivel of nanoscale columns of AlxGa1-xN/AlN around c-axis according to the data of XRD pole figure measurements. Results obtained in our work show promising capabilities in the use of SiC/porSi/сSi substrates for integration of silicon technology and technology of synthesis of the nanoscale columnar AlxGa1-xN heterostructures by molecular-beam epitaxy with plasma-activated nitrogen.

We carried out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen plasma activation on a hybrid substrate containing layers of silicon carbide and porous silicon. Using X-ray diffractometry, Raman and photoluminescence spectroscopy, it is shown that thin films formed on a hybrid substrate have minimal residual stresses and intense photoluminescence.

In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid substrate containing layers of silicon carbide and porous silicon. Using X-ray diffractometry, Raman and photoluminescence spectroscopy, it is shown that thin films formed on a hybrid substrate have minimal residual stresses and intense photoluminescence.

The peculiarities of the phase composition and electronic structure of aluminum–silicon composite films near the Al 0.75 Si 0.25 composition obtained by the magnetron and ion-beam sputtering methods on a Si(100) silicon substrate are studied using the X-ray diffraction techniques and ultrasoft X-ray emission spectroscopy. In addition to silicon nanocrystals of about 25 nm in size, an ordered solid solution corresponding to the previously unknown Al 3 Si phase is formed in magnetron sputtering on a polycrystalline Al matrix. Films obtained by ion-beam sputtering of the composite target are found to be monophasic and contained only one phase of an ordered solid solution of aluminum silicide Al 3 Si of the Pm3m cubic system with the primitive cell parameter a = 4.085 Å. However, subsequent pulsed photon annealing of the composite with different radiation doses from 145 to 216 J/cm 2 gives rise to the partial decomposition of the Al 3 Si phase with the formation of free metallic aluminum and silicon nanocrystals with sizes in the range from 50 to 100 nm, depending on the pulsed photon radiation dose.

Исследованы фазовый состав и электронное строение композитных пленок Al-Si вблизи состава Al0.75Si0.25 на подложке Si(100), полученных магнетронным и ионно-лучевым напылением. При магнетронном напылении в поликристаллической Al матрице образуются нанокристаллы кремния размерами ~25 нм и упорядоченный твердый раствор Al3Si кубической сингонии Рm3m с параметром примитивной ячейки a = 4.085 Å. Пленки, полученные ионно-лучевым напылением, однофазны и содержат только упорядоченный твердый раствор Al3Si. При этом образование фазы Al3Si сопровождается изменением характера распределения плотности Al 3s-состояний. Вместо параболического характера роста плотности состояний в нижней и средней части валентной зоны (как в чистом металле) наблюдается почти линейный. Аналогичный эффект отмечается для Si 3s-состояний. Кроме того, взаимодействие атомов Al и Si приводит к уменьшению плотности Al 3s-состояний вблизи уровня Ферми в результате перехода части электронов на более электроотрицательные атомы кремния. Селективное вытравливание алюминия в случае магнетронной пленки приводит к формированию нанопористой губчатой структуры, а для ионно-лучевой пленки селективное травление не приводит к появлению развитой морфологии, что подтверждает ее однофазность. Последующий импульсный фотонный отжиг (ИФО) ионно-лучевых пленок дозами 145-216 Дж/см2 приводит к частичному распаду фазы Al3Si с формированием металлического алюминия и нанокристаллов кремния с размерами 50-100 нм в зависимости от дозы ИФО. Последующее травление образца, подвергнутого ИФО, ведет к получению развитой нанопористой структуры. Работа выполнена при поддержке Минобрнауки России в рамках государственного задания ВУЗам в сфере научной деятельности на 2017-2019 годы. Проект № 3.6263.2017/ВУ.

Morphology of the top-down grown silicon nanowires obtained by metal-assisted wet-chemical approach on silicon substrates with different resistance were studied by scanning electron microscopy. Obtained arrays of compact grown Si nanowires were a subject for the high resolution electronic structures studies by X-ray absorption near edge structure technique performed with the usage of high intensity synchrotron radiation of the SRC storage ring of the University of Wisconsin-Madison. The different oxidation rates were found by investigation of silicon atoms local surrounding specificity of the highly developed surface and near surface layer that is not exceeded 70 nm. Flexibility of the wires arrays surface morphology and its composition is demonstrated allowing smoothly form necessary surface oxidation rate and using Si nanowires as a useful matrixes for a wide range of further functionalization.

Ni rods distributed in silicon dioxide matrix formed on silicon wafers have been characterized by means of scanning electron microscopy and X–ray absorption near edge structure (XANES) spec troscopy. Ni rods have been obtained by electrochemical deposition of the metal onto a silicon dioxide matrix pores formed with the tracking technique. Latent tracks have been obtained by SiO2 film irradiation with heavy gold ions at the Hahn–Meitner–Institute (Berlin, Germany). Scanning electron microscopy has established the peculiarities of pore filling with metal and the specificity of Ni rod formation and their morphology (surface and cleavages). High intensity synchrotron radiation of the Helmholtz Zentrum Berlin has been used in the ultrasoft X–ray range for electron energy structure studies of the Ni rods with the XANES technique. The specific phase composition of the surface layers has been investigated using Si, Ni and O atom local surrounding analysis performed based on synchrotron XANES technique data including the rod/matrix interface. Possible Ni silicide formation has been demonstrated for a certain rod array formation mode in which partial SiO2 matrix destruction occurs and the metal contacts with the silicon wafer. Natural oxidation specificity has also been studied for the Ni rod/SiO2 heterostructure surface.

AbstractThe peculiarities of the phase composition and electronic structure of aluminum–silicon composite films near the Al_0.75Si_0.25 composition obtained by the magnetron and ion-beam sputtering methods on a Si(100) silicon substrate are studied using the X-ray diffraction techniques and ultrasoft X-ray emission spectroscopy. In addition to silicon nanocrystals of about 25 nm in size, an ordered solid solution corresponding to the previously unknown Al_3Si phase is formed in magnetron sputtering on a polycrystalline Al matrix. Films obtained by ion-beam sputtering of the composite target are found to be monophasic and contained only one phase of an ordered solid solution of aluminum silicide Al_3Si of the Pm3m cubic system with the primitive cell parameter a = 4.085 Å. However, subsequent pulsed photon annealing of the composite with different radiation doses from 145 to 216 J/cm^2 gives rise to the partial decomposition of the Al_3Si phase with the formation of free metallic aluminum and silicon nanocrystals with sizes in the range from 50 to 100 nm, depending on the pulsed photon radiation dose.

The problem of the efficiency of the controllable formation of arrays of silicon nanoparticles is studied on the basis of detailed investigations of the electronic structure of multilayer nanoperiodic a-SiO x /SiO2, a-SiO x /Аl2О3, and a-SiO x /ZrO2 compounds. Using synchrotron radiation and the X-ray absorption near edge structure (XANES) spectroscopy technique, a modification is revealed for the investigated structures under the effect of high-temperature annealing at the highest temperature of 1100°C; this modification is attributed to the formation of silicon nanocrystals in the layers of photoluminescent multilayer structures.

Изучен вопрос эффективности контролируемого формирования массивов кремниевых наночастиц на основе детальных исследований электронного строения многослойных нанопериодических структур a-SiOx/SiO2, a-SiOx/Al2O3 и a-SiOx/ZrO2. С применением синхротронного метода спектроскопии ближней тонкой структуры края рентгеновского поглощения обнаружена модификация исследованных структур под влиянием высокотемпературного отжига при максимальной температуре 1100oC, объясняемая образованием нанокристаллов кремния в слоях светоизлучающих многослойных структур. DOI: 10.21883/FTP.2017.03.44208.8374

The electronic structure of SOI (silicon-on-insulator) with strained and unstrained silicon layers was theoretically calculated and experimentally investigated by means of Ultrasoft X-ray Emission and Absorption Spectroscopy. According to the experimental results, an additional spectral feature occurs in the strained silicon layer density of states near the bottom of the conduction band (E-c). The shift of E-c towards the top of the valence band, as well as smoothing of the density of states and disappearance of the degenerate minimum between L'(2v) and L-1v valence band states was also observed.The theoretical calculations have been performed by full potential linearized augmented plane-wave method and show that straining of silicon lattice leads to a slight shifting of the conduction band bottom towards the top of the valence band and causes an increase in the density of states between L'2 and Li,. The theoretical shift of the conduction band bottom is substantially less than the experimental one. (C) 2016 Elsevier B.V. All rights reserved.

The results of X-ray absorption near-edge structure spectroscopy data obtained with synchrotron radiation for multilayered nanoperiodic Al2O3/SiO x /Al2O3/SiO x /.../Si(100) structures annealed at temperatures of 500–1100°C are reported. The data show that, upon high-temperature annealing (∼1100°C), the structures are modified. The modification is attributed to the formation of Si nanocrystals in deep layers of the structures. At the same time, the structures exhibit size-dependent high-intensity photoluminescence in the photon-energy range 1.4–1.52 eV.

Wire-like SnO 2 micro- and nanocrystals prepared by gas-transport synthesis have been studied by X-ray photoelectron spectroscopy and X-ray absorption near edge structure spectroscopy with the use of synchrotron radiation. It has been found that the heat treatment in ultrahigh vacuum affects the surface state and the vacancy formation in surface layers of the wire-like crystals.

Silicon wires arrays have been produced by metal-assisted wet chemical etching with the use of crystalline silicon substrates. The arrays and individual nanowires have been studied by scanning and transmission electron microscopy. The electronic structure and phase composition of the surface and near-surface layers of the arrays have been studied by ultrasoft X-ray emission spectroscopy. It is shown that the morphologically more developed sample formed on a substrate with low resistivity is considerably more strongly subject to oxidation with noticeable formation of phases of intermediate silicon oxides. The array of nanowires formed on a substrate with high resistivity also undergoes natural oxidation, but does so to a substantially lesser extent and, with increasing depth of analysis, mostly contains the phase of crystalline silicon constituting the bulk of the nanowires being formed.