Explore the vast range of titles available.

The Raman scattering intensity of oriented polyvinyl alcohol (PVA) films doped with cadmium sulfide and iodine is found to depend on the position of the sample with respect to the direction of the exciting radiation polarization. This dependence agrees with the supposed polymer structure of the inorganic component of the complex and the Raman scattering mechanism with its participating similar to the surface-enhanced Raman spectroscopy (SERS). The spectra are found to contain bands similar to the G- and Dâbands of carbon materials in the Raman shift range 1000-2000 cm.sup.-1. The origin of these bands is discussed.

Heterostructures of Bi 2 Se 3 topological insulators were epitaxially grown on graphene by means of the physical vapor deposition at 500 °C. Micrometer-sized flakes with thickness 1 QL (quintuple layer ~ 1 nm) and films of millimeter-scale with thicknesses 2–6 QL had been grown on CVD graphene. The minimum thickness of large-scaled continuous Bi 2 Se 3 films was found to be ~ 8 QL for the regime used. The heterostructures with a Bi 2 Se 3 film thickness of > 10 QL had resistivity as low as 200–500 Ω/sq and a high room temperature carrier mobility ~ 1000–3400 cm 2 /Vs in the Bi 2 Se 3 /graphene interface channel. Moreover, the coexistence of a p -type graphene-related conductive channel, simultaneously with the n -type conductive surface channel of Bi 2 Se 3 , was observed. The improvement of the bottom Bi 2 Se 3 /graphene interface with the increase in the growth time clearly manifested itself in the increase of conductivity and carrier mobility in the grown layer. The grown Bi 2 Se 3 /G structures have lower resistivities and more than one order of magnitude higher carrier mobilities in comparison with the van der Waals Bi 2 Se 3 /graphene heterostructures created employing exfoliation of thin Bi 2 Se 3 layers. The grown heterostructures demonstrated the properties that are perspective for new functional devices, for a variety of signal processing and logic applications.

The results of the study of the crystal structure of CaSi 2 films and their polymorphic transformations, depending on production conditions involving radiation-stimulated CaSi 2 formation during heat treatment of a CaF 2 layer, are presented in this contribution. CaSi 2 films with space group were obtained by exposing the CaF 2 layer to an electron beam, both directly during the epitaxial growth of CaF 2 and after the formation of CaF 2 films of various thicknesses. In both cases, at the initial stage of epitaxial growth with thin CaF 2 films (10 nm), the resulting CaSi 2 film is characterized by space group with a three-layer translational period of silicon substructures in the unit cell (tr3). As the CaF 2 film thickness increases, the CaSi 2 film formed via the radiation-stimulated process is characterized by space group with a six-layer translational period of silicon substructures in the unit cell (tr6). Analysis of the results obtained in this work, together with literature data, leads to the conclusion that the incorporation of F into the silicide lattice stabilizes the formation of CaSi 2 films with space group corresponding to a specific polytype.

It has been shown that there is a significant difference in the stoichiometry of the complexes of fully and partially saponified poly(vinyl alcohol) (PVA) with lithium chloride and bromide. This phenomenon is explained based on the concept of hybrid interpolymer complexes. In the Raman spectra of the complexes, a single band is observed at 1445 cm –1 .

The aim of the paper is to present and substantiate a technique to visualize DEA modelling results without any loss of mathematical rigour. The proposed family of parametric optimization methods allows one to construct an intersection of the multidimensional frontier with a two-dimensional plane determined by any pair of given directions. This approach reduces the efficiency analysis of production units to the investigation of well-known functions in economics. We also propose constructive methods to calculate marginal rates of substitution, marginal rates of transformation and so on.

MIS structures with a nonstoichiometric oxide dielectric and a transparent top electrode are attracting attention for use as low-cost Schottky-diode-based solar cells, photodetectors, and photomemristors. Previously, attempts were made to use both thin tunnel layers of silicon oxide or rather thick silicon-rich oxides for these purposes. This work is the first attempt to use films of nonstoichiometric germanosilicate films in photosensitive MIS structures.

Electron beam annealing was carried out to form amorphous and crystalline germanium clusters in GeO[SiO] and GeO[SiO 2 ] films deposited on quartz and mono crystalline silicon substrates. Using electron microscopy, Raman spectroscopy, and light transmission and reflection spectroscopy, the structural transformations of the films and their optical properties were studied. From the analysis of Raman spectra, it was shown that amorphous germanium nano clusters are present in the as-deposited GeO[SiO] film, while they are not observed in the as- deposited GeO[SiO 2 ] film. Regimes of electron beam annealing which are necessary for the formation of germanium nano crystals in GeO[SiO] and GeO[SiO 2 ] films were found. It was shown that, at the same annealing parameters, the fraction of the crystalline phase of germanium in GeO[SiO] films were smaller than in GeO[SiO 2 ] films. In addition, it was found that the fraction of the crystalline phase at the same annealing parameters is larger for films on a quartz substrate than on monocrystalline silicon substrate. The sizes of germanium nanocrystals formed as a result of electron beam annealing were determined from Raman spectra analysis. The proposed method of obtaining amorphous germanium nanoclusters and nanocrystals in films of nonstoichiometric germanosilicate glasses using electron beam annealing can be used to create ordered arrays of such nanostructures.

The creation of a new universal nonvolatile memory is one of the most actual problems in nanoelectronics. Recently, it has been believed that memristors are one of the most promising devices for creating such memory. A memristor is a device with two contacts in which it is possible to controllably and reproducibly switch between resistance states by passing current pulses. The search for new materials for memristors is proceeding on a broad front; materials with low bond enthalpy, such as germanium and tin oxides, are promising for reducing switching energy. It is also expected that the use of multilayer structures will help improve the performance of memristors. Nonstoichiometric germanosilicate glass (GeSi x O y ) films and many-layer structures based on them were deposited using high-vacuum electron beam vapor deposition. The GeO 2 , SiO, SiO 2 , or Ge powders were co-evaporated and deposited onto p +-Si(001) substrate (held at room temperature) with resistivity ρ = 0.002 Ω cm. The transparent in visible and near infrared range indium-tin-oxide (ITO) contact was deposited as the top electrode, and memristor metal-insulator-semiconductor (MIS) structures were fabricated. Then the MIS structures were annealed at temperature 500°C. The as-deposited and annealed MIS structures were studied by Fourier-transformed infrared (FTIR) spectroscopy and Raman spectroscopy. The current-voltage characteristics ( I – V ) and resistive switching cycles of the MIS have been studied. The advantages of GeSi x O y based memristors are: low voltage for ON and OFF switching; they do not require a preliminary special “forming” procedure; the appearance of intermediate resistance states, what is perspective for producing of multibit and “analogous” memristors.

Heterostructures of Bi.sub.2Se.sub.3 topological insulators were epitaxially grown on graphene by means of the physical vapor deposition at 500 °C. Micrometer-sized flakes with thickness 1 QL (quintuple layer ~ 1 nm) and films of millimeter-scale with thicknesses 2-6 QL had been grown on CVD graphene. The minimum thickness of large-scaled continuous Bi.sub.2Se.sub.3 films was found to be ~ 8 QL for the regime used. The heterostructures with a Bi.sub.2Se.sub.3 film thickness of > 10 QL had resistivity as low as 200-500 â¦/sq and a high room temperature carrier mobility ~ 1000-3400 cm.sup.2/Vs in the Bi.sub.2Se.sub.3/graphene interface channel. Moreover, the coexistence of a p-type graphene-related conductive channel, simultaneously with the n-type conductive surface channel of Bi.sub.2Se.sub.3, was observed. The improvement of the bottom Bi.sub.2Se.sub.3/graphene interface with the increase in the growth time clearly manifested itself in the increase of conductivity and carrier mobility in the grown layer. The grown Bi.sub.2Se.sub.3/G structures have lower resistivities and more than one order of magnitude higher carrier mobilities in comparison with the van der Waals Bi.sub.2Se.sub.3/graphene heterostructures created employing exfoliation of thin Bi.sub.2Se.sub.3 layers. The grown heterostructures demonstrated the properties that are perspective for new functional devices, for a variety of signal processing and logic applications.

Results of an experimental study of gold-induced crystallization of thin films of amorphous germanium (a-Ge) are reported. The Raman spectroscopy and optical microscopy are applied to study the influence of the initial thickness of the a-Ge film on the morphology of the material obtained by means of annealing of bilayer Au/a-Ge structures. The a-Ge/Au thickness ratios equal to 1.1 and 2.3 are considered. Low-temperature annealing of quartz/Au/a-Ge samples is performed in a high-vacuum atmosphere (10 −4 Pa) at a temperature of 300°C for 24 h. The Raman spectroscopy results show that sample annealing leads to complete crystallization of a-Ge with formation of polycrystalline germanium (poly-Ge) in both bottom and upper layers of the samples. For the sample with a-Ge/Au = 2.3, a continuous poly-Ge film is obtained on the substrate due to implementation of the layer exchange mechanism. In this case, poly-Ge hillocks are formed in the upper layer of the sample due to a-Ge crystallization in the presence of Au. For the sample with a-Ge/Au = 1.1, a non-continuous poly-Ge film with a coverage degree of 30 % is formed in the bottom layer. The poly-Ge material is formed in the upper layer due to the processes of “explosive” crystallization and secondary crystallization induced by Au.