We report on the electric transport properties of Si heavily doped with Sb at concentration just below the insulator-to-metal transition in the temperature range 1.9-3.0 K for current density J < ...0.2 A cm
. The change in the sign of the temperature dependence of the differential resistivity Formula: see text was observed: the dFormula: see text/dT is positive if J < 0.045 A cm
whereas it becomes negative at J > 0.045 A cm
. The effect is explained assuming the exchange by electrons between the upper Hubbard band (UHB) and the conduction band. The obtained J dependencies of the activation energy, nonequilibrium concentration, mobility and scattering time of the conduction electrons correspond well to this hypothesis. The reason for charge instability is the Coulomb repulsion between electrons occupying states both in the UHB and conduction band. The estimated J dependencies of the conduction electrons lifetime and concentration of the D
states in the UHB strongly supports this assumption.
The present work focuses on the study of properties of hafnium oxide (HfO2) films, deposited by reactive magnetron sputtering of the Hf target in Ar/O2 gas mixture. The X-ray diffraction analysis of ...the deposited films proved the amorphous structure of the films, which was also confirmed by the Raman spectroscopy.
It was determined that as the HfO2 film thickness had been decreased from 98.6 nm to 13.5 nm, film density had dropped from 9.52 to 9.26 g/cm2. At the same time, the dielectric constant dropped from 21.3 to 8.0 units, and the dielectric loss tangent rose, especially at high frequencies. At the same time, the decrease in film thickness resulted in increased leakage currents at low electric field density E, and decreased leakage currents at high E. Improvement of dielectric characteristics and increase in leakage current with film thickness growth is a consequence of film densification and the formation of a crystalline phase. Thickness dependence of the dielectric constant is associated with the violation of the ionic polarization mechanism at the film electrode interface.
•Amorphous hafnium oxide films were deposited by reactive magnetron sputtering.•The deposited films are characterized by high uniformity and low surface roughness.•With a decrease of the film thickness, its dielectric characteristics drop.•This is due to a violation of the ionic polarization at the film interface.
We investigate the electron spin resonance of an ensemble of Nitrogen-Vacancy color centers in a bulk diamond crystal obtained by CVD-method. The diamond crystal had 1 ppm concentration of nitrogen. ...The four possible orientations of the NV-center in the crystal lattice lead to different dependences of a magnitude and an orientation of the external static magnetic field. We used the field of 35 Gauss with the vector in the plane of the crystal. We could rotate it to a certain angle within almost 360 degrees around the normal vector to the plane of the crystal. The goal was to define the unknown orientations of the four axes of the NV-centers relatively to the crystal plane. Experimental results obtained at room temperature with a continuous microwave excitation and presented in this paper are in a good agreement with our simulations.
It is shown that artificial radioactivity can be initiated under conditions of a glow-discharge plasma. When analyzing the isotopic and elemental composition in the near-surface region of
and
...cathodes, initial and those treated for 40 hours under conditions of deuterium- or protium-containing plasma, changes were detected, respectively, in the isotopic ratios of
and
impurity isotopes in the
cathode and of
,
, and
in the
cathode, as well as a significant reduction in the amount of these impurity elements in the cathodes and the formation of
isotopes in the
cathode. Possible nuclear processes that cause the established artificial radioactivity are considered.
A highly accurate method for modeling InAlAs/InGaAs MHEMT transistors of the UHF frequency range with a gate length of 0.15 μm is considered. This method takes into account the nonlinear dependences ...of the internal parameters on the applied voltages. It is established that the maximal error of modeling is not larger than 1.5% in the frequency range from 1 to 50 GHz.
Sol–Gel Derived Photonic Crystals BaTiO3/SiO2 Gaponenko, N. V.; Kholov, P. A.; Karnilava, Yu. D. ...
Semiconductors (Woodbury, N.Y.),
11/2021, Letnik:
55, Številka:
11
Journal Article
Recenzirano
It is shown for the first time that multilayer periodic BaTiO
3
/SiO
2
structures formed by the sol–gel method are tunable photonic crystals with dependence of the photonic band gap from the ...temperature of the sample. The shift of the minimum in the reflection spectrum in the photonic band gap is observed from 616 to 610 nm in the sample-temperature range from +184 to +24°C, respectively, and is reproduced for several samples synthesized at a temperature of 450°C.
The possibility of using chemical vapor deposition (CVD) graphene as a 2D buffer layer for epitaxial growth of III-nitrides by plasma assisted-MBE on amorphous substrates (SiO2 prepared by thermal ...oxidation of Si wafer) was investigated. The comparative study of graphene-coated parts of the wafers and the parts without graphene was carried out by scanning electron microscopy and X-ray diffractometry. It was shown that epitaxial GaN and AlN films with close to 2D surface morphology can be obtained by plasma assisted-MBE on amorphous SiO2 substrates with a multilayer graphene buffer using the HT AlN nucleation layer.
This paper studies the design of a nonlinear model of AlGaAs/InGaAs/GaAs рHEMT microwave-frequency range transistors with a gate length of 0.15 µm using parametric analysis methods. In the ...calculations, not only nonlinear current sources but also the dependences of the nonlinear gate-source and gate-drain capacitances on voltages are studied. It is shown that the proposed model makes it possible to describe the IV characteristics of the studied device adequately in the range of drain currents from 0 to 100 mA and the frequency range from 5 to 45 GHz. The error of the model does not exceed 3%.
The spectra of the optically detected magnetic resonance for single NV
–
centers have been experimentally studied in two solid-state samples in the range of hyperfine interactions between the ...electron spin and the nitrogen nucleus spin in the same NV
–
center. This study has been aimed at reaching a maximal microwave frequency resolution in the experimental setup used. For measurements, two low-nitrogen (no higher than 50 ppb) diamond single-crystal samples have been grown. Measured time
of the spin decoherence in NV
–
centers was about 2 μs in one sample and 20 μs in the other. For both samples, the spectrum of the optically detected magnetic resonance for the hyperfine splitting of a single NV
–
center and
14
N atom has been taken and investigated. The resolution in these samples has been estimated at a level of 3.5 and 0.18 MHz, respectively. It has been noted that the resolution of the spectrum improves with increasing time
of the spin decoherence of the single NV
–
center.
The possibility of initiation of nuclear chemical processes in the Pb cathode during a glow discharge in a low-temperature deuterium-containing nonequilibrium plasma leading to a significant (at ...times) decrease in the isotope content of some impurity elements (specifically, Zn) and increasing others (specifically, W, Fe, Mn, and Al). Such processes can be understood by introducing the existence in nuclear matter of metastable non-nucleon excitations of internal shaking (
isu
-states) formed by initiating actions on the nuclei of electrons with high (on chemical scales) kinetic energy
E
e
~ 3–5 eV.
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