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.

The results of investigations on crystallization of silicon nanoclusters in a-SiOx matrix have shown that, even at the very fast annealing using pulse photonic annealing (PPA) formation of rather large silicon crystallites (> 100 nm) occurs, as well as the arrays of Si nanocrystals with average sizes of -10 nm and small sizes of -1-2 nm happens. It is shown that with an increase in the concentration of nanoclusters in the initial film from 15 to 53%, the contribution of large crystals (larger than 100 nm) increases from 15% (at 15% ncl-Si) to 65% (at 53% ncl-Si), which says on an increase in the probability of coalescence of crystallites into substantially larger ones with an increase of ncl-Si content in the initial film, despite the high annealing speed.

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.

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.

Physics, Chemistry and Applications of Nanostructures, pp. 124-127 (2015) No AccessELECTRONIC AND ATOMIC STRUCTURE OF SILICON NANOCRYSTALS IN ALUMINUM MATRIX AND WITHOUT ITV. A. TEREKHOV, D. S. USOLTSEVA, S. Yu. TURISHCHEV, I. E. ZANIN, B. L. AGAPOV, A. A. LESHOK and P. S. KATSUBAV. A. TEREKHOVVoronezh State University, Universitetskaya 1, 394006 Voronezh, Russia, D. S. USOLTSEVAVoronezh State University, Universitetskaya 1, 394006 Voronezh, Russia, S. Yu. TURISHCHEVVoronezh State University, Universitetskaya 1, 394006 Voronezh, Russia, I. E. ZANINVoronezh State University, Universitetskaya 1, 394006 Voronezh, Russia, B. L. AGAPOVVoronezh State University, Universitetskaya 1, 394006 Voronezh, Russia, A. A. LESHOKBelarusian State University of Informatics and Radioelectronics, P. Browka 6, 220013 Minsk, Belarus and P. S. KATSUBABelarusian State University of Informatics and Radioelectronics, P. Browka 6, 220013 Minsk, Belarushttps://doi.org/10.1142/9789814696524_0032Cited by:0 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail Abstract: Al–Si nanocomposites have been produced by magnetron sputtering of a compound target onto a silicon substrate. Nanostructured silicon films have further been obtained by selective removal of aluminum. It has been found that silicon particles are nanocrystals with the mean size of 20-25 nm, which surface is covered by an amorphous layer with a thickness of ~5 nm. The band structure (in particular, near the bottom of the valence band) of the nanocomposite films was found to differ from the bulk material because of an influence of the aluminum matrix. After the aluminum removal, the valence band structure becomes identical to that in the bulk material. FiguresReferencesRelatedDetails Physics, Chemistry and Applications of NanostructuresMetrics History PDF download

The films have been deposited on the silicon subtracts with the (111) and (100) orientations by thermal evaporation of SiO powder and carbon implanted with doses of 6 · 1016 to 1,2 · 1017 cm−2 followed by annealing in nitrogen at 1100 oC. Diffraction studies of these structures confirm the occurrence of a preferred orientation in the nanocrystals during high temperature thermal annealing, controlled by the substrate orientation. It was possible to detect the existence of two arrays of silicon nanocrystals in the dielectric matrix, with one having a smaller average size of 5—10 nm and a lattice parameter close to that of crystalline silicon, and the other one having a large size of 50—100 nm and a greater lattice parameter. We have estimated the carbon implantation doses for which the large size nanocrystals (> 50 nm) do not form. This dose is 6 · 1016 cm−2 for the (111) substrates and 9 · 1016 cm−2 for the (100) ones.

Films of Al-Si nanocomposites produced by magnetron evaporation of a complex target onto a silicon substrate have been investigated using scanning electron microscopy, X-ray diffraction, ultrasoft X-ray emission spectroscopy, and X-ray absorption near edge structure spectroscopy. It has been found that silicon inclusions are nanocrystals with the mean size of 20–25 nm, with the surface covered by an amorphous silicon layer. The presence of the aluminum matrix in the initial films changes their band structures, in particular, near the bottom of the valence band. After the removal of aluminum, the structure of the valence band becomes identical to that in the bulk material and the structure of the conduction band indicates the presence of a disordered surface layer with a thickness of ∼5 nm.

The X-ray diffraction investigations have been performed for nanocomposite materials based on porous aluminum oxide with inclusions of TGS and TGS, which is doped with L ,α-alanine (ATGS). The presence of the TGS and ATGS textures in pores of Al 2 O 3 films has been found. It has been established that, under conditions of confined geometry, the broadening of diffraction maxima of the reflection is caused by the size effect. The temperature dependences of the order parameter for porous aluminum oxide with TGS inclusions have been constructed.

Films obtained using molecular-beam deposition of SiO powder on c -Si (111) substrates for the purpose of SiO2 system formation with silicon nanocrystals were investigated before and after 900–1100°C annealing by photoluminescence, ultrasoft X-ray emission spectroscopy, X-ray photoelectron spectroscopy, X-ray absorption near-edge structure spectroscopy, and X-ray diffraction. The appearance of (111)-oriented luminescent silicon nanoclusters in considerable amounts upon annealing at T = 1000–1100°C is established in the investigated films. An anomalous phenomenon of X-ray absorption quantum yield intensity reversal for the L 2,3 elementary silicon edge is detected. Models for this phenomenon are suggested.

Films obtained using molecular‐beam deposition of SiO powder on c‐Si (111) substrates for the purpose of SiO2 system formation with silicon nanocrystals were investigated before and after 900–1100 °C annealing by photoluminescence, ultrasoft X‐ray emission spectroscopy, X‐ray photoelectron spectroscopy, X‐ray absorption near edge structure spectroscopy and X‐ray diffraction. The appearance of (111) oriented luminescent silicon nanoclusters in considerable amounts on annealing at 1000–1100 °C is established in the investigated films. An anomalous phenomenon of the X‐ray absorption quantum yield intensity inversing for the L2, 3 elementary silicon edge is detected. Models for this phenomenon are suggested. Copyright © 2010 John Wiley & Sons, Ltd.

The dielectric properties of composite structures based on porous aluminum with inclusions of triglycine sulphate and Rochelle salt were investigated. The effect of structured and adsorbed water on the dielectric behavior of the nanocomposite under study was found.

The nature of epitaxial intergrowth of black (β) and red (α) modifications of zinc diphosphide is studied. The intergrowth of single crystals is shown to be caused by that the atoms-analogs form almost identical structural motifs in both structures. The black modification grows on the (001) plane of the red one so that its b axis is parallel to the (110) plane of α-ZnP 2 .

Copper specimens (coins) found at the bottom of Taman bay, which lied in water for about 1600 years, manifested a very high corrosion resistance. The uniqueness of the phenomenon is attributed to the heightened concentration of hydrogen sulfide caused by the activity of mud volcano in this region. Under the layer of insoluble corrosion products, namely copper sulfides and disulfides, the items preserved the original surface relief.

Structure of Cd3P2 (P42/nmc, a = b = 8.7390 Å, c = 12.2523 Å) has been solved and refined up to R = 3.78% using precision X-ray diffraction experimental data (λ-MoK α, graphite monochromator on a primary beam, 11529 reflections). Interatomic distances and valence angles are determined. Phosphorus forms a face-centered cubic lattice in which 3/4 tetrahedral voids are occupied by cadmium atoms in the crystal structure. The structure can be described by two equivalent models in which the positions of cadmium atoms, which occupy tetrahedral voids following the “diamond principle,” are preserved, while the remaining free and occupied voids change their places.

The lattice constants of Al x Ga 1− x As epitaxial alloys with various AlAs ( x ) contents are determined for Al x Ga 1− x As/GaAs(100) heterostructures grown by MOC-hydride epitaxy using X-ray diffractometry and an X-ray back-reflection method. An ordered AlGaAs 2 (superstructural) phase is found in epitaxial heterostructures with x ≈ 0.50. The lattice constant of this phase is smaller than the lattice constants of an Al 0.50 Ga 0.50 As alloy and GaAs single-crystal substrate.

The refined data on the crystal structure of Zn 3 P 2 ( I ) provide evidence for a tetrahedral coordination of metal atoms, which is characteristic of covalent structures with sp 3 -hybridized orbitals. Deformation-electron-density maps for crystal I , which were constructed from high-precision X-ray diffraction data, confirm the predominantly covalent character of bonds in this compound. The deformation-density maps clearly show covalent bridges with their peaks shifted toward electronegative phosphorus atoms. The longer the bond, the larger the shift. The presence of delocalized electrons indicates that the bonding mechanism is partially metallic.

The structure of Zn3P2 (P 42/nmc, a = b = 8. 0785 Å, c = 11. 3966 Å) was solved and refined to R = 3. 2% in a precision X-ray diffraction experiment (λ-MoKa, graphite monochromator on a primary beam, 27,496 reflections) . Interatomic distances and bond angles have been determined. The fcc lattice of the structure is built from phosphorus atoms, and the zinc atoms occupy 3/4 of all tetrahedral voids; the structure is described by two equivalent models where 1/4 occupied (by zinc atoms) and 1/4 vacant voids change places. The zinc atoms that occupy the voids following the diamond principle do not change places.

With the aim of studying the characteristic features of chemical interactions between atoms in the α (red tetragonal) and β (black monoclinic) modifications of zinc diphosphide, the maps of deformation electron-density distribution at the P-P and P-Zn bonds were constructed from precision X-ray diffraction data. The P-P bonds were demonstrated to be of a pronounced covalent nature. The maxima in the Zn-P bonds are shifted to the electronegative phosphorus atom, which is indicative of a mixed ionic-covalent nature of the bond, with the ionicity being higher in the α than in the β modification. Based on the dependence of the contribution of the metallic component on the delocalized electron density, it was concluded that the contribution of the metallic component is more pronounced in the black than in the red modification. An increase in the bond ionicity and the absence of delocalized electrons result in an increase in the forbidden gap in the red modification compared to its increase in the black modification.

The crystal structure of decamethylruthenocene (η5-C5Me5)2Ru (I) is investigated by X-ray diffraction. It is demonstrated that the compound studied crystallizes in two polymorphic modifications, namely, modification Ia with space group P21/m (Z = 2) in the temperature range 153–300 K and modification Ibwith space group P21/n (Z = 4) at 203 K. No temperature phase transition between the modifications is found. In crystal Ia, the molecule occupies a special position in the mirror plane. In crystal Ib, the molecule is located in the general position. The cyclic ligands η5-C5Me5, (Cp*) are aligned parallel to each other and adopt an eclipsed conformation. The bond lengths in compounds Ia and Ib are identical. Analysis of the anisotropic displacement parameters of the atoms indicates that molecules Ia and Ib are not structurally rigid and that the Cp* rings involved in these molecules can execute independent librations. In the temperature range 153–300 K, the Cp*(1) ligand in molecule Ia is statically disordered over two positions. The barrier heights B5 for rotation of the Cp* ligands are estimated both from the root-mean-square amplitudes of librations 〈ϕ2〉 and with the use of the atom-atom potential method.