The temperature dependence (in range from 24 to 290 K) of Raman spectroscopy of the Cu2ZnSnSe4 (CZTSe) films with Zn-rich (series A) and Zn-poor (series B) composition obtained on a Ta foil is investigated. Analisys and approximation by the Lorentz function of the CZTSe Raman spectra suggests that the CZTSe most intense Raman peak consists of two modes (at 192/189 and 194/195 cm(-1)), which are slightly shifted from each other. In addition, the Raman peaks around 192 and 189 cm(-1) lead to asymmetric broadening of dominant peaks at 194 and 195 cm(-1) in Raman spectra of the CZTSe films series A and B, respectively. In the case of the Sn-rich CZTSe films, we attribute of Raman peak around 189 cm(-1) to SnSe2 compound. However in the case of the Sn-poor CZTSe films, the observable shift is too high to assign confidently the 192 cm(-1) band to a SnSe2 compound, which was not detected by XRD analysis. We suppose that this mode is attributed to disordered kesterite structure. The temperature dependence Raman spectra for both series of the CZTSe films shows that a change temperature from 290 to 24 K leads to position shift and narrowing of the CZTSe Raman A-modes. The calculated temperature coefficients and anharmonic constants in Klemens model approximations for temperature dependence of shift position and FWHM of the CZTSe A-modes shown that four-phonon process has dominant contribution in damping process and as a consequence in Raman spectrum changes for two series of the CZTSe films.

Transformations of structural defects, the hydrogen state, and electrophysical properties of silicon treated in hydrogen plasma are studied. Treatment in plasma (150°C) produces bands in Raman spectra at 2095 and 2129 cm –1 that are associated with scattering by Si–H vibrations. Subsequent heat treatment (275°C) causes a band for gaseous molecular H 2 to appear at 4153 cm –1 . A comparison of Raman spectra and scanning probe microscopy results shows that hydrogenation forms defects (platelets) of average size 43 nm and surface density 6.5·10 9 cm –2 that are due to precipitation of H 2 and formation of Si–H bonds. Inclusions of average size 115 nm and surface density 1.7·10 9 cm –2 that are filled with molecular H 2 are observed after heat treatment. The concentration of free charge carriers remains constant after treatment in plasma and subsequent heat treatment.

Recently, researchers showed great interest on SnS1−xSex alloy films because of their tunable physical properties that are suitable as an absorber layer in thin film solar cells. In the present work, SnS1−xSex thin films were deposited by thermal co-evaporation of SnS and Se at different substrate temperatures ranging from 200 to 350 °C. The influence of substrate temperature (Ts) on composition, structure, surface morphology, topography and optical properties of as-deposited films was investigated using appropriate techniques and the results are reported in detail. The EDS analysis of SnS1−xSex films showed that Sn/(S + Se) ratio was changed from 0.84 to 1.16 with increase of substrate temperature. All the films were polycrystalline in nature, exhibiting (111) plane as preferred orientation with orthorhombic crystal structure. From W–H analysis, the crystallite size and lattice strain in the films were evaluated, where the crystallite size varied in the range, 9–22 nm with substrate temperature. The layers showed a change in the shape of grains with the rise of substrate temperature, where the grain size has increased with Ts. The topographical results indicated an indirect relation between surface roughness and average grain size with change in substrate temperature. The band gap energy values of the films was decreased with increase of Ts and varied in the range, 1.59–1.46 eV. In addition, the photoconductivity measurements revealed that the as-deposited SnS1−xSex films had bimolecular type recombination (γ ~ 0.5) of photo-generated charge carriers.

The structural and optical properties of ZnO:Eu thin films deposited on silicon and glass substrates by the magnetron sputtering method have been studied by scanning electron microscopy, energy dispersive X-ray analysis, Auger electron spectroscopy, Raman spectroscopy and photoluminescence measurements. Intense red emission of Eu3+ dopant in ZnO films is issued by the band-to-band excitation and energy transfer from the host ZnO to europium ions.

Recently, researchers showed great interest on SnS 1− x Se x alloy films because of their tunable physical properties that are suitable as an absorber layer in thin film solar cells. In the present work, SnS 1− x Se x thin films were deposited by thermal co-evaporation of SnS and Se at different substrate temperatures ranging from 200 to 350 °C. The influence of substrate temperature ( T s ) on composition, structure, surface morphology, topography and optical properties of as-deposited films was investigated using appropriate techniques and the results are reported in detail. The EDS analysis of SnS 1− x Se x films showed that Sn/(S + Se) ratio was changed from 0.84 to 1.16 with increase of substrate temperature. All the films were polycrystalline in nature, exhibiting (111) plane as preferred orientation with orthorhombic crystal structure. From W–H analysis, the crystallite size and lattice strain in the films were evaluated, where the crystallite size varied in the range, 9–22 nm with substrate temperature. The layers showed a change in the shape of grains with the rise of substrate temperature, where the grain size has increased with T s . The topographical results indicated an indirect relation between surface roughness and average grain size with change in substrate temperature. The band gap energy values of the films was decreased with increase of T s and varied in the range, 1.59–1.46 eV. In addition, the photoconductivity measurements revealed that the as-deposited SnS 1− x Se x films had bimolecular type recombination ( γ ~ 0.5) of photo-generated charge carriers.

The paper presents studies of optical and electrical properties of SnS1-xSex (x = 0.26-0.31) thin films deposited on glass substrates using thermal co-evaporation technique at different substrate temperatures, 200 degrees C-350 degrees C. The as-deposited films were characterized by the energy dispersive spectroscopy, X-ray diffractometry, scanning electron microscopy, optical transmission and reflection spectroscopy, four-probe resistivity and photoconductance measurements. The results have shown that deposited films can be used as absorber layers in thin film solar cell applications, and the optimal substrate temperature for the deposition is 300 degrees C.

AbstractCu_2ZnSnSe_4 thin films are produced by selenizing electrochemically layer-by-layer deposited and preliminarily annealed Cu–Zn–Sn precursors. For flexible metal substrates, Mo and Ta foils are used. The morphology, elemental and phase compositions, and crystal structure of Cu_2ZnSnSe_4 films are studied by scanning electron microscopy, X-ray spectral microanalysis, X-ray phase analysis, and Raman spectroscopy.

Cu 2 ZnSnSe 4 thin films are produced by selenizing electrochemically layer-by-layer deposited and preliminarily annealed Cu–Zn–Sn precursors. For flexible metal substrates, Mo and Ta foils are used. The morphology, elemental and phase compositions, and crystal structure of Cu 2 ZnSnSe 4 films are studied by scanning electron microscopy, X-ray spectral microanalysis, X-ray phase analysis, and Raman spectroscopy.

Cu2ZnSnS4 (CZTS) thin films were synthesized by sulfurization of subsequently electrochemically deposited Cu/Sn/Zn metal precursors on Mo foil substrates in melted sulfur on air at the temperature of 440 degrees C close to the sulfur boiling point for 1 h. The films contain only CZTS phase with lattice parameters a = 5.422 +/- 0.002 angstrom and c = 10.811 +/- 0.006 angstrom and components at. % ratio: Cu/(Sn + Zn) = 1.05, Zn/Sn = 1.22, (Cu + Sn + Zn)/S = 0.93. The film surface is densely packed without cracks or pinholes. The obtained results show the practical ability to obtain CZTS thin films by a novel technically simple and low-cost liquid-based process. (C) 2018 Elsevier B.V. All rights reserved.

Raman spectroscopy was used to study the structural properties of graphene synthesized by chemical vapor deposition using decane (C10H22) as a precursor at various hydrogen concentrations. Reduction of the carrier gas flow rate from 150 cm3/min to zero changes the average spacing between the defects from 53 to 212 nm and the average grain size from 87 to 798 nm and changes the uniformity and continuity of the graphene layer. The obtained relationships can be used to control the defectiveness, homogeneity, and continuity of the graphene layer of the coating during synthesis by this method.

Low-temperature Raman studies of supported graphene are presented. A linear temperature dependence of 2D peak linewidths was observed with the coefficients of 0.036 and 0.033 cm ^-1 /K for graphene on copper and glass substrates, respectively, while G peak linewidths remained unchanged throughout the whole temperature range. The different values observed for graphene on glass and copper substrates were explained in terms of the substrate effect on phonon–phonon and electron–phonon interaction properties of the material. The results of the present study can be used to consider substrate effects on phonon transport in graphene for nanoelectronic device engineering.

We investigated correlation between structure and electron transport properties of composite films synthesized by the ion-beam sputtering of Cu + SiO2 target. Photoluminescence (PL) spectra testify to an oxygen deficiency in the silicon dioxide matrix in agreement with the Raman spectroscopy, which reveals the presence of CU2O phase along with elemental copper. For the nanocomposites with copper atomic fraction x < 0.64, the temperature dependence of conductivity obeys ln(sigma) similar to T(-0.5 )law at low temperatures (electron tunneling between size distributed copper nanoparticles) replacing with the Mott Variable Range Hopping (VRH) with the temperature increase. Electron transport properties of the studied nanocomposites are significantly affected by matrix defectiveness, which increases with metallic phase content according to PL study. The increasing matrix defectiveness results in decrease of crossover temperature from tunneling to VRH conductivity, as well as growth of matrix permittivity due to an enhanced contribution of electrons localized at defects. (C) 2017 Elsevier B.V. All rights reserved.

CVD-graphene on silicon was irradiated by accelerated heavy ions (Xe, 160 MeV, fluence of 10(11) cm(-2)) and characterized by Raman spectroscopy. The defectiveness of pristine graphene was found to be dominated by grain boundaries while after irradiation it was determined by both grain boundaries and vacancies. Respectively, average inter-defect distance decreased from similar to 24 to similar to 13 nm. Calculations showed that the ion irradiation resulted in a decrease in charge carrier mobility from similar to 4.0 x 10(3) to similar to 1.3 . 10(3) cm(2)/V s. The results of the present study can be used to control graphene structure, especially vacancies concentration, and charge carrier mobility.

Electron transport in (Fe0.45Co0.45Zr0.10)(x)(Al2O3)(1-x) granular nanocomposites (NCs) produced by the ion beam sputtering of compound target was studied in the temperature range of 2-300 K. Conductivity of the films synthesized in the inert (Ar) atmosphere is determined below percolation threshold by the thermally activated electron tunneling over metallic granules at low temperatures and replaced by the Mott variable range hopping (VRH) with increasing temperature. Introduction of oxygen to the sputtering chamber suppresses VRH leading to retention of the thermally activated tunneling in the whole studied temperature range for the metallic phase atomic concentrations up to x = 0.62. The model of thermally activated tunneling over metallic granules gives an excellent agreement with experimental data when alumina matrix permittivity is considered as increasing with concentration of the metallic phase fraction in the films, which is due to increase in number of localized electronic states. The established influence of the sputtering atmosphere on the electron transport in nanocomposites is explained by reduction of concentration of the defects in matrix when oxygen is added to the sputtering atmosphere. (C) 2017 Elsevier B.V. All rights reserved.

Raman spectroscopy and Monte-Carlo simulation studies for supported graphene irradiated by 160 MeV Xe ions are presented. Changes in the density and dominating types of defects with increasing fluence were observed. In order to analyze contribution of defect formation mechanisms, in which the substrate is involved, a comparative study was performed for graphene on SiO2/Si, copper and glass substrates. The major defining mechanisms were found to be atomic recoils and formation of defects induced by hot electrons. For graphene on copper, the impact of substrate recoil atoms was found to be greater comparing to graphene on silicon oxide and glass, where the recoils participated approximately equally. Moreover, a possibility of defect formation in graphene due to hot electrons generated in the substrate near the interface was noted. Finally, a linear dependence of air-induced doping on D and G peak intensity ratio that represents defect density in graphene was found. The study is useful for solving the long-standing controversy on major mechanisms of defect formation in irradiated graphene, as well as for graphene-based nanoelectronic device engineering.

PbxSn(1−x)S (0.05<x<0.20) thin films with the thickness of 2μm were deposited on glass substrates using hot wall vacuum deposition method at the vacuum pressure of 5×10−4Pa, wall temperature of 600°С, substrate temperature of 300°С and subsequently annealed at 450°C in vacuum at 5×10−4Pa. The microstructure and optical properties of the as-deposited and annealed films were examined in relation to the film composition. The explanations of lattice parameter deviations from the bulk crystals for both as-deposited and annealed PbxSn(1−x)S thin films are discussed. The PbxSn(1−x)S thin films exhibit a preferred orientation around the [111] direction. The annealing decreases the film microstrain values and increases the grain size and the degree of preferred orientation. Thermal probe measurements showed the sulfur-deficient films to be p-type and the sulfur-rich films to be n-type. The PbxSn(1−x)S films exhibit direct allowed transitions with energy band gap Eg(d) increasing with the increase of Pb mole fraction. The Eg(d) values for as-deposited films range from 0.95 to 0.98eV and for annealed films they variy from 0.90 to 0.94eV.

Linear G peak position temperature dependence in Raman spectra of graphene synthesized by chemical vapor deposition from decane on copper (220) with a shift factor of −(5.4 ± 0.4) × 10 −2 cm −1 K −1 was observed. The obtained value substantially exceeds values previously obtained for graphene by other authors, and was associated with the substrate interaction effects.

The interfacial oxidant flux comprises two distinct components. One of them does not depend on time, and its value equals to 2.5 × 1012 cm−2 s−1 O2 molecules. The other term increases reciprocally with the positive square root of time.