Optical characteristics of the HfO
2 −
x
N
x
and TiO
2 −
x
N
x
films obtained by reactive ion beam sputtering have been investigated by spectral ellipsometry. The chemical composition of the films ...was determined using X-ray photoelectron spectroscopy. The nitrogen content in the oxynitride films (determined by the N
2
/O
2
ratio in the gas mixture during synthesis) reached ≈9 at % for TiO
2 −
x
N
x
and ≈ 6 at % for HfO
2 −
x
N
x
. It is found that the dispersion relations
n
(λ) and
k
(λ) for the TiO
2 −
x
N
x
films change from those characteristic of titanium dioxide to those typical of titanium nitride with an increase in the nitrogen content from 0 to ≈9 at %. The optical parameters of the HfO
2 −
x
N
x
films depend weakly on the nitrogen content in the range 0–6 at %.
A promising candidate for universal memory, which would involve combining the most favourable properties of both high-speed dynamic random access memory (DRAM) and non-volatile flash memory, is ...resistive random access memory (ReRAM). ReRAM is based on switching back and forth from a high-resistance state (HRS) to a low-resistance state (LRS). ReRAM cells are small, allowing for the creation of memory on the scale of terabits. One of the most promising materials for use as the active medium in resistive memory is hafnia (HfO\(_2\)). However, an unresolved physics is the nature of defects and traps that are responsible for the charge transport in HRS state of resistive memory. In this study, we demonstrated experimentally and theoretically that oxygen vacancies are responsible for the HRS charge transport in resistive memory elements based on HfO\(_2\). We also demonstrated that LRS transport occurs through a mechanism described according to percolation theory. Based on the model of multiphonon tunneling between traps, and assuming that the electron traps are oxygen vacancies, good quantitative agreement between the experimental and theoretical data of current-voltage characteristics were achieved. The thermal excitation energy of the traps in hafnia was determined based on the excitation spectrum and luminescence of the oxygen vacancies. The findings of this study demonstrate that in resistive memory elements using hafnia, the oxygen vacancies in hafnia play a key role in creating defects in HRS charge transport.
A technology is developed for producing thin films of CuGaSe
2
by the method of two-step selenization when the reaction component (selenium) is delivered by a flow of a carrier gas (nitrogen). The ...effects of the temperature of selenization on the surface morphology, composition, and structure of CuGaSe
2
films are studied by electron microscopy and X-ray-diffraction phase analysis. Based on X-ray photoelectron spectroscopy data on the transformation of chemical states of the components, the influence of the temperature of selenization on the phase-formation process in films is analyzed.
The paper presents a detailed investigation of the thermal transport of the Ni50Mn28Ga22-x(Cu, Zn)x (x = 0; 1.5) alloys through specific heat, thermal diffusivity and thermal conductivity ...measurements. It is shown that the partial replacement of Ga atoms by Zn or Cu atoms leads to a convergence of magnetic and martensitic phase transition temperatures. Our measurements of the thermal diffusivity and thermal conductivity revealed that the behavior of these parameters in the phase transitions region is anomalous due to the coexistence of martensite-austenite phases and the effect of the latent heat of the phase transition. Moreover, the latent heat plays a crucial role in the appearance of a deep minimum of thermal diffusivity in the region of martensitic transformation for the Cu- and Zn-doped samples. Estimates of the phonon mean free path lph in martensitic and austenitic phase gave values of lph,mart = 1.5 nm and lph,aust = 1.9 nm, respectively. This implies that the main mechanism of phonon scattering is local structural inhomogeneities, which decrease sharply upon transition from martensite phase to the highly symmetric austenitic phase.
•The mechanisms of heat transfer near the martensite-austenite phase transition in Ni50Mn28Ga22-x(Cu, Zn)x (x = 0; 1.5) alloys was investigated.•Abnormal behavior of thermal diffusivity and thermal conductivity was found for samples with Cu and Zn.•The phonon mean free path in the martensitic and austenitic phases were estimated.
Estimates of the conventional proven hydrocarbon reserves show a tendency toward depletion, and in the near future they will be insufficient to meet the ever-growing global energy demand. The problem ...of crude oil deficiency can be solved by involving unconventional hydrocarbon resources in both recovery and refinery. However, the hydrogen deficiency of heavy oil and natural bitumen requires technical and technological solutions. Therefore, the hydrogen-donating capacity of water and solvents, particularly in reservoir conditions, is very attractive. In this paper, we study the hydrogen-donating capacity of naphthenic and polar solvents during hydrothermal treatment of heavy oil from Ashal’cha reservoir (Republic of Tatarstan, Russia). It was established that naphthenic solvents significantly influence the viscosity reduction due to the destructive hydrogenation of resins and asphaltenes. Among naphthenic solvents, decalin significantly increases the amount of evolved gases, particularly C4–C10 isomers and aromatics. However, the maximum evolved gases among all of the used solvents correspond to formic acid. The results of elemental analysis revealed that the H/C ratio rises in crude oil samples after hydrothermal treatment in the presence of cyclohexane and decalin. FT-IR spectral indices revealed an increase in crude oil aliphaticity in case of using solvents from the cyclohexane–tetralin–decalin series due to the cleavage of carbon–heteroatom bonds in aliphatic substitutes of resins and asphaltenes. Significant changes in the FT-IR spectra of crude oil are observed in the presence of tetralin.
Developments in titanium nickelide compression devices for forming interintestinal junctions in colorectal surgery are analyzed. Preference in developments has been given to compression devices made ...of titanium nickelide wire materials. The authors linked the main advantages with simplicity of use, small size, high levels of biological and physical sealing, and better conditions for tissue regeneration. Questions related to the means of establishing the primary patency of compression anastomoses and optimizing anastomosis techniques remain unanswered.
This paper presents methods that can be used in order to determine the relative remanent magnetization and uniaxial magnetic anisotropy constant of particles in powder-based permanent magnets using ...Mossbauer spectroscopy. The methods were verified on the permanent magnet barium ferrite.
—
Polycrystalline CuIn
0.95
Ga
0.05
Se
2
films are obtained by a two-step procedure of the controlled selenization of intermetallic CuIn
0.95
Ga
0.05
layers. The effect of the selenization ...temperature and the selenized intermetallic-film thickness on the structure and electrophysical properties of the formed selenide films is studied. With an increase in the selenization temperature, the degree of imperfection of the polycrystalline films is shown to decrease and the efficiency of Ga incorporation into the crystal lattice is shown to increase. Based on the results of studying the electrophysical properties of synthesized samples, the nature of the microstructure effect on the current-transfer mechanisms in polycrystalline CuIn
0.95
Ga
0.05
Se
2
films is discussed.
