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Multifractal characterization of epitaxial silicon carbide on silicon

Abstract

The purpose of this study was to investigate the topography of silicon carbide films at two steps of growth. The topography was measured by atomic force microscopy. The data were processed for extraction of information about surface condition and changes in topography during the films growth. Multifractal geometry was used to characterize three-dimensional micro- and nano-size features of the surface. X-ray measurements and Raman spectroscopy were performed for analysis of the films composition. Two steps of morphology evolution during the growth were analyzed by multifractal analysis. The results contribute to the fabrication of silicon carbide large area substrates for micro- and nanoelectronic applications.

Open access
High Pressure Raman Study of Layered Semiconductor Tlgase2

Abstract

Raman spectroscopy measurements of a monoclinic layered semiconductor TlGaSe2were performed in a pressure range up to 10.24 GPa. The pressure-induced first-order phase transition accompanied by reconstruction of the layer structure was observed at the pressure P ~ 0.9 GPa. The mode-Grüneisen parameters of intralayer bonds were calculated for TlGaSe2. The contribution of thermal expansion to temperature changes of phonon frequencies was defined. The type of intralayer bonds and their pressure transformation were analyzed in layered TlGaSe2. It was shown that the nature of intramolecular forces in molecular crystals and intralayer forces in layered GaS, GaSe and TlGaSe2is similar

Open access
Research into the relationship between the surface topography, texture and mechanical properties of PVD-Cu/Ni multilayers

Abstract

The paper presents the results of structural examinations and mechanical tests of Cu/Ni multilayers fabricated by the magnetron sputtering method. The investigated multilayers were differentiated by Ni sublayer thickness (1, 3 and 6 nm), while the retaining Cu sublayer thickness was unchanged (2 nm). Measurements demonstrated that the multilayers were strongly textured in the direction of their growth [111], with the thinnest multilayer (Cu/Ni = 2/1) showing a stronger texture. Stronger texturing was associated with greater surface roughness. Multilayers with the largest thickness had higher hardness and Young’s modulus. The properties of Cu/Ni multilayers depended both on the thickness of their sublayers, as well as on their total thickness.

Open access
Effect of substrate temperature on the electrical and optical properties of electron beam evaporated indium antimonide thin films

Abstract

Thin films of non-stoichiometric indium antimonide (In0.66Sb0.34) have been deposited by electron beam evaporation technique on glass substrates at different substrate temperatures, (300–473 K). The films have polycrystalline nature with zinc blende structure. The decrease in electrical resistivity with increasing temperature shows semiconducting behavior. Hall measurements indicate that the films are of n-type. Optical transmission spectra of as deposited thin films have been measured at different substrate temperatures. All the electrical parameters i.e. electron mobility (µ), carrier concentration (n), resistivity (ρ), activation energy and band gap (E g) have been found to be temperature dependent. Suitable explanations are given in the paper.

Open access
Superconductivity at 9.5 K in the Ti2GeC compound

Abstract

We report on the investigation of the Ti2GeC properties by X-ray diffraction, magnetic and electrical resistivity measurements. Polycrystalline samples of Ti2GeC with nominal compositions were prepared by solid state reaction. X-ray powder patterns suggest that all peaks can be indexed with the hexagonal phase of Cr2AlC prototype. The temperature dependence of both electrical resistivity and magnetization indicate a bulk type-II superconductivity at 9.5 K. Magnetoresistive data suggest an upper critical field of Bc2 ∼ 8.1 T and coherence length ∼ 61 ° Å. Furthermore, the results highlight the highest critical temperature reported up to now for an H-phase.

Open access
Characterization of carbon deposit with controlled carburization degree

Abstract

Promoted nanocrystalline iron was carburized in a differential tubular flow reactor with thermogravimetric measurement of mass changes. The carburization process was carried out in the presence of pure methane under atmospheric pressure at 650 °C to obtain different carburization degrees of the sample. The carburized iron samples were characterized by the X-ray diffraction, high-resolution transmission electron microscope in the energy-dispersive X-ray spectroscopy mode, thermoprogrammable oxidation, and Raman spectroscopy. As a result of the methane decomposition on the nanocrystalline iron the following nanocrystalline products were observed: iron carbide Fe3C, graphite, iron and nanotubes. The crystallinity of the samples increased with the carburization degree.

Open access
Role of molybdenum ions in lead zinc phosphate glass system by means of dielectric studies

Abstract

PbO-ZnF2-P2O5 glasses doped with different mol% (0.1 to 1.0) of MoO3 have been prepared. Dielectric properties ∊(ω), tanδ, σAC, of the synthesized samples were calculated from frequency measurements versus temperature. Space charge polarization was used to analyze the temperature and frequency dispersions of dielectric constant ∊(ω) and dielectric loss tanδ. Quantum mechanical tunneling model was employed to explain the origin of AC conductivity. The AC conductivity exhibited an increasing trend with increasing concentration of MoO3 (up to 0.2 mol%) but the activation energy for conduction decreased. The plots of AC conductivity revealed that the relaxation dynamics depends on MoO3 dopant concentration.

Open access
One-pot synthesis of magnetic γ-Fe2O3 nanoparticles in ethanol-water mixed solvent

Abstract

Maghemite (γ-Fe2O3) nanoparticles were synthesized via a low-temperature solution-based method using ferric chloride hexahydrate and ferrous chloride tetrahydrate as precursors in the mixed solvent of ethanol and water. X-ray diffraction, energydispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy revealed that the obtained product was pure γ-Fe2O3. Transmission electron microscopy showed the morphology of the nanoparticles to be approximately spherical in shape with an average diameter of 11 nm. Magnetization measurements indicated the dry powders exhibit ferromagnetic behavior with a maximum saturation magnetization of 41.1 emu/g at room temperature.

Open access
Properties of AlN thin films deposited by means of magnetron sputtering for ISFET applications

Abstract

This work presents the investigations of AlN thin films deposited on Si substrates by means of magnetron sputtering. Nine different sputtering processes were performed. Based on obtained results, the tenth process was prepared and performed (for future ISFET structures manufacturing). Round aluminum (Al) electrodes were evaporated on the top of deposited layers. The MIS capacitor structures enabled a subsequent electrical characterization of the AlN films by means of current-voltage (I-V) and capacitance-voltage (C-V) measurements. Based on these results, the main parameters of investigated layers were obtained. Moreover, the paper describes the technology of fabrication and electrical characterization of ISFET transistors and possibility of their application as ion sensors.

Open access
Estimation of optical parameters of silicon single crystals with different orientations

Abstract

Optical properties of Si single crystals with different orientations (1 0 0) and (1 1 1) were investigated using spectrophotometric measurements in a spectral range of 200 nm to 2500 nm. The data of optical absorption revealed an indirect allowed transition with energy gap of 1.1 ± 0.025 eV. An anomalous dispersion in refractive index. The normal dispersion of the refractive index was discussed according to Wemple-DiDomenico single oscillator model. The oscillator energy Eo, dispersion energy Ed, high frequency dielectric constant ∈, lattice dielectric constant ∈L and electronic polarizability α e were estimated. The real ∈1 and imaginary ∈2 parts of dielectric constant were also determined.

Open access