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The transient processes in the electric conduction of fine disperse 2D-MoS2 powder samples, occurring at changing voltages applied to the sample under the conditions of uniaxial compression, have been studied. The long-term transient changes in conduction occurring both after switching on and off the applied voltage were observed. The current–voltage characteristics have a hysteresis of branches corresponding to increasing and decreasing voltages. The observed results are explained within the frame of the migration (interlayer) polarization model. [ABSTRACT FROM AUTHOR]

The features of electric transport in the powder samples consisting of the nanosize 2D-MoS2 flakes with different number of layers have been studied under the conditions of uniaxial pressure. There have been measured current-voltage characteristics at the room temperature in the voltage range of 0 through 1.5 V at three magnitudes of the uniaxial pressure from 0.5 through 2.5 MPa. The current-voltage characteristics are shown to be non-linear and to form a loop during successive increasing and decreasing voltage. The long-term decays of the current on applying voltage to the sample and of the voltage on the sample in the no-load mode on switching off have been observed. The observed results are explained by the model of the surface charge accumulation causing polarization. [ABSTRACT FROM AUTHOR]

We present the results of experimental and theoretical studies of the surface plasmon polariton excitations in heavily doped GaN epitaxial layers. Reflection and emission of radiation in the frequency range of 2–20 THz including the Reststrahlen band were investigated for samples with grating etched on the sample surface, as well as for samples with flat surface. The reflectivity spectrum for p-polarized radiation measured for the sample with the surface-relief grating demonstrates a set of resonances associated with excitations of different surface plasmon polariton modes. Spectral peculiarities due to the diffraction effect have been also revealed. The characteristic features of the reflectivity spectrum, namely, frequencies, amplitudes, and widths of the resonance dips, are well described theoretically by a modified technique of rigorous coupled-wave analysis of Maxwell equations. The emissivity spectra of the samples were measured under epilayer temperature modulation by pulsed electric field. The emissivity spectrum of the sample with surface-relief grating shows emission peaks in the frequency ranges corresponding to the decay of the surface plasmon polariton modes. Theoretical analysis based on the blackbody-like radiation theory well describes the main peculiarities of the observed THz emission. [ABSTRACT FROM AUTHOR]

Effects of tin doping on crystallization of amorphous silicon were studied using Raman scattering, Auger spectroscopy, scanning electron microscopy, and X-ray fluorescence techniques. Formation of silicon nanocrystals (2-4 nm in size) in the amorphous matrix of Si1-xSnx, obtained by physical vapor deposition of the components in vacuum, was observed at temperatures around 300 °C. The aggregate volume of nanocrystals in the deposited film of Si1-xSnx exceeded 60% of the total film volume and correlated well with the tin content. Formation of structures with ∼80% partial volume of the nanocrystalline phase was also demonstrated. Tin-induced crystallization of amorphous silicon occurred only around the clusters of metallic tin, which suggested the crystallization mechanism involving an interfacial molten Si:Sn layer. [ABSTRACT FROM AUTHOR]

In the p-Si0.88Ge0.12/Si heterostructures with quantum wells delta-doped by boron, the decay kinetics of the lateral infrared photoconduction has been studied at low temperatures (15 to 50 K). Photoconduction was excited in the impurity spectral range by a CO2-laser pulse radiation. After switching off the light, both positive and negative residual photoconductions are observed. It is positive at low temperatures, but it changes to the negative one at T > 25 K. The higher the temperature and electric field are, the faster is the decay of the negative residual photoconduction. Qualitative explanation and quantitative description of the photoconduction relaxation take into account the competition between the recombination of free holes on the impurity levels and their thermal excitation from barrier traps into subbands of the quantum well. If the recombination time is much smaller than the excitation time from the traps, the negative residual photoconduction appears. [ABSTRACT FROM AUTHOR]

The influence of thermal ionization of an impurity delta-doped layer situated either in the center or on the edge of a quantum well (QW) on impurity binding energy is investigated theoretically for the case of Si0.8Ge0.2/Si QW. It is shown that the Hartree potential created by free electrons and by ionized impurities at high temperatures superimposes on the original (at low temperature) QW energy profile. Resulting new QWs have their own impurity binding energies. It is of interest that energies are nearly the same for center- and edge-doped QWs, contrary to those at low temperatures. The obtained results are explained on the basis of Coulomb's law when decreasing the mean distance between free electron and impurity atom with temperature involves an increase in the impurity binding energy. [ABSTRACT FROM AUTHOR]

Electric transport properties and magnetoresistance (MR) of the array of metallic single-wall carbon nanotube bundles irradiated by the electron flux with the energy close to 1 MeV or Co60 gamma quanta have been investigated within the temperature range T = 1.8…200 K and in the magnetic fields up to 5 T. The power-law behavior of the conduction vs temperature was observed within the range 50 to 200 K, which is typical for conduction of quasi-one-dimensional systems in the model of the electron gas as the Luttinger liquid. The change in power exponent a with the radiation dose and its deviation as compared to α for the non-irradiated samples is related with changing the number of conduction channels in the bundles as a consequence of the radiation defects appearance. At the temperatures below 50 K, the Mott three-dimensional hopping conduction is realized. Using the measured dependence of conduction on the temperature and electric field, the density of electron states in the vicinity of the Fermi level, which participate in the hopping charge transport, and the localization length of charge carriers in these states have been determined. These parameters determining the hopping mechanism of the charge transport are noted to depend on the radiation dose. The magnetoresistance in the Mott-type hopping conduction region was negative in the whole range of magnetic fields, while at the large fields an upturn to the positive change was observed. The mechanisms both of the negative and positive MR components are discussed. [ABSTRACT FROM AUTHOR]