Electric conductivity of electron-bombarded single crystals of KCl-RbCl solid solutions

We present the results of investigations of the influence of divalent cation impurities on the radiative changes in the electric conductivity of RbCl crystals and KCl-RbCl solid solutions bombarded by electrons. It was observed that a temperature dependence of the electic conductivity of the bombarded crystals has a complicated form in this case. In the case of crystals containing no cation impurities of different valence, there is no radiative decrease of the electric conductivity due to the action of the Smoluchowski mechanism, and a sharp increase is observed instead. We consider physical properties that lead to the appearance of a maximum in the temperature dependence of the electric conductivity of the bombarded crystals.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 92–96, December, 1970.     

СВОЙСТВА СУРЬМЯНИСТОГО КАДМИЯ, ЛЕГИРОВАННОГО СЕРЕБРОМ, ПРИ НИЗКИХ ТЕМПЕРАТУРАХ

The temperature dependence of the resistivity and the Hall coefficient of Ag doped CdSb single crystals was investigated in the temperature range of 1.5–300°K. It was shown that Ag in CdSb gives shallow acceptor levels with an activation energyE _a =3.5×10^–3 eV. Presence of the admixture band determines the electrical properties of crystals at low temperatures. The energy width of this band is about 10^–3 eV for slightly doped crystals.     

Luminescence centres in pure AgCl crystals

The temperature dependence and the influence of pressure on band width of blue-green luminescence were measured in pure AgCl crystals. The comparison of results obtained with other published data support the existence of two luminescence centres (in the temperature ranges between 130–160°K and between 20–30°K).     

Peculiar aspects of galvonamagnetic properties of InS single crystals

The electrical conductivity and the Hall effect in electronic InS single crystals have been studied over a wide range of temperatures, from 150 K to 800 K, and their peculiarities have been elucidated. At temperatures of 200 K the Hall coefficient passes through a maximum but does not reach a minimum. The peculiarities of the temperature dependence of the Hall coefficient are explained within the two-band model, which incorporates the conduction band and the impurity band. The parameters of the impurity band have been determined. The hopping mechanism of scattering has been found to predominate in InS single crystals in the temperature range 150–270 K, and at temperatures of 270 K to 400 K the mobility is limited, mainly by scattering on impurity ions. Above 400 K electrons are scattered on polar lattice vibrations.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 29–34, January, 1989.     

Radiative electronic transitions in ZnTe∶Al,Ga, in crystals

We report the results of studies on the concentration dependence of the cathodoluminescence of ZnTe:Al, Ga, In crystals in the temperature range 4.2–300 K. A band with maximum at 2.2 eV and half-width of the order of 70 MeV and a band with maximum at 2.36 eV and half-width 1 MeV appear in ZnTe:Al crystals at 4.2 K. In the temperature range 40–70 K we detected the structure of the first band such that the separation of the maxima of the resolved bands corresponded to the energy of an LO phonon. A band with maximum at 1.8 eV was found to appear in ZnTe:Ga crystals at 4.2 K and a band with maximum at 1.9 eV appeared in ZnTe:In crystals at that temperature. The donor activation energies were determined to be 0.11, 0.30, and 0.25 eV, respectively, for aluminum, gallium, and indium.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 82–86, October, 1987.     

Electrical conductivity and photoconductivity of single crystals of lithium hydride

Nonactivated LiH crystals and crystals of LiH with Mg, In, Tl, Sn, Sb, and Bi impurities are investigated. Photoconductivity is found in luminescent crystals. The temperature dependence of the electrical conductivity and photoconductivity in the temperature range of 100–570 ° K is measured. Volt-ampere characteristics of the dark current and photocurrent in fields up to 10⁴ V/cm at various temperatures are obtained. Data is presented on the inertia of the photocurrent and its dependence on the intensity of the exciting light. Conclusions are drawn concerning some connection of LiH photoconductivity with the type of activating impurity, the absence of a connection with the brightness of the luminescence, and the specific role of photoconductivity in color centers.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 10, pp. 94–98, October, 1971.     

Probability of electron emission in photoemission from doped semiconductor

Electron motion is investigated in a strong-field region —in the region of bending of the band close to the surface of a semiconductor. In this region there is a change in the electron distribution function under the action of the electric field and interaction mechanisms leading to energy loss of the hot electrons. The main characteristics of the external photoeffect are determined by the energy lost by the electron in the region of band bending and the size of the barrier at the semiconductor-vacuum interface. The electron-emission probability from a crystal containing a space-charge region is determined from the solution of the Boltzmann kinetic equation. The energy dependence of the energy scattering length of the hot electrons is taken into account in the calculation. The calculation is made for photoemission from GaAs in conditions when the interaction with polar optical phonons is the most effective energy-scattering mechanism. An expression is obtained for the energy distribution function of the emitted electrons for the case of strong electric fields. The position of the distribution-function maximum depends on the electric field and the effective interaction constant with phonons. The current and quantum yield of the photoeffect are calculated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 81–87, October, 1978.In conclusion, it remains to extend profound thanks to V. L. Bonch-Bruevich for Ms constant interest in the work.     

Detection of the plasmon photoeffect of alkali metals in photoelectron energy distribution curves

A new explanation is proposed for the experimental results obtained from measuring photoelectron energy distributions in alkali metals. The explanation is based on the idea of the plasmon photoeffect. The plasmon photoeffect consists of the excitation of plasmons by light in a solid, and the decay of the plasmons in turn excites the electrons. In a vacuum these photoelectrons form groups of electrons with different energies. The plasmon photoeffect provides a significantly better explanation of the structure of the experimental data than the usual photoeffect.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 82–87, October, 1973.     

Calculation of the concentration of the Mössbauer element and the probability of resonant absorption from the electronic nuclear-gamma-resonance spectrum

A method is proposed for calculating the concentration of the Mössbauer element or the probability of resonant absorption from the electronic nuclear-gamma-resonance spectrum of a multicomponent sample, taking account of the photoeffect at atoms of all the elements appearing in its composition. The method allows calculations to be performed with a relative error of approximately 10–20%, using data on the photoeffect cross sections at atoms of the elements of which the samples consist and the energies of the resulting photoelectrons.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 42–49, November, 1983.     

Dislocation structure of kcl crystals grown with vibration of the melt

Summary The amplitude at all frequencies was 0.04 mm. Three crystals were grown at each frequency, with seeds of dislocation density D = 6 × 10⁴ cm^–2. Figure 1 shows the frequency dependence of the final D. Each point in Figs. 1 and 2 is the mean from 50 measurements (50 fields of view). At all frequencies except 180 Hz, D was 2–4 times less than that without vibration, while at 100 and 160 Hz it was less by nearly an order of magnitude.The effects of amplitude (0.02 to 0.2 mm) were examined at 100 Hz, the minimum D occurring at 0.1 mm (Fig. 2). At 0.04–0.08 mm, D was less by a factor 3–4 than for crystals grown without vibration, while at 0.1 mm it was less by an order of magnitude, being 2 × 10^–4 cm^–2. The size of the etch pits on crystals grown at amplitudes up to 0.1 mm did not differ from that for crystals grown at rest, but above 0.1 mm the size increased, by more than a factor 3 at 0.2 mm. Figure 3 illustrates these effects.Optimal vibration reduces D by improving the growth conditions (reduction of temperature gradients by mixing, more uniform impurity distribution).     

Investigation of heterojunctions in the system SnO2-CdGeP2

Photosensitivity spectra of heterojunctions on the basis of SnO₂ layers and n- and p-type conductivity CdGeP₂ crystals are investigated in natural and linearly polarized radiation in the 160–360 K temperature range. Temperature coefficients of the change in interband energies of A- and B-junctions are determined. The temperature dependence of the photosensitivity of the obtained n-n and n-p-heterojunctions is studied.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 23–27, July, 1989.     

Current carrier mobility in manganese-doped cadmium telluride

The possibility of substantial influence of a manganese impurity on the magnetic and optical properties of CdTe, which is explained by the state and interaction of the Mn 3d⁵-electron spins in the CdTe crystal lattice, is shown in [1–3]. An investigation of the influence of the Mn impurity on current carrier scattering in this material is of interest. To this end, the temperature dependence of the Hall mobility of electrons in CdTe-Mn single crystals is investigated in this paper in the temperature range 77–435°K.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 24–28, April, 1982.     

The control of gap width in the low-dimensional systems with charge density waves instability

The strong photoeffect was discovered experimentally in InSe crystals at temperature 4.2 K as a result of laser radiation action at fixed wavelengths of 337 and 195 micron. Effect was explained with appearance of the gap in the continuum of conduction band. The photoeffect value was found to depend strongly on electric current through the crystal.     

Birefringence of SbSI and SbSeI crystals at the region of antiferroelectric phase transition

Anomalous behavior has been observed in the temperature range of T = 140–145 °C. The electric current I(T) of SbSI and SbSeI crystals along the c(z) axis changes significantly at the region of the antiferroelectric phase transition when DC voltage is applied. The peak positions are observed at 140 °C and 145 °C for SbSI and SbSeI, respectively. The birefringence spectra show temperature-dependent changes upon retardation m, confirming the antiferroelectric phase transition for both crystals. The peak positions observed from the optical measurements do not differ from the electrical measurements, showing the transition point at 140?°C and 145?°C for SbSI and SbSeI, respectively.     

Temperature dependence of the stationary photocurrent in doped sillenite type crystals

The temperature dependence of the photocurrent in doped sillenite-type crystals is investigated in the temperature range 80–300°K. In the region of low temperatures thermally activated photocurrent is observed, while at high temperatures quenching is observed. In a number of specimens the temperature quenching section is absent. The results are explained within the framework of a multilevel recombination model involving slow and fast recombination centers as well as capture levels.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 85–89, June, 1985.     

Thermal expansion of anharmonic crystals composed of inert gases

The temperature dependence of the lattice constant and linear expansion coefficient for inert gas crystals are determined using the second-order approximation of Bogolyubov's temperature expansion. It is shown that when the temperature dependence of the Gruneisen constant is taken into account the agreement with experiment is improved over the thermodynamic perturbation theory and the theory based on a multiplicative binary distribution function.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 44–47, April, 1976.     

Preparation and basic physical properties of BiTeI single crystals

A modified Bridgman method is described, which makes it possible to prepare homogeneous BiTeI crystals using excess iodine. At room temperature the values of the electrical conductivity of the crystals range around 2000 ^–1 cm^–1, the Hall constant value about 0·09 cm^–3 coul^–1, the Seebeck coefficient about 50 V K^–1. In connection with the assumption of super-stoichiometric iodine content we expect there exist point defects in the crystals, where Te atoms are replaced with I atoms, which gives rise to electric conductivity. On the basis of the temperature dependence of the electron mobility one can suppose a mixed mechanism of the scattering of the free carriers by the acoustic branch of lattice vibrations and by ionized impurities.     

Optical properties and interband transitions in the layered compounds SbI3

The optical constants of SbI₃ single crystals, prepared from solution, were calculated from normal incidence reflectance data via a Kramers-Kronig analysis. The dependence of the absorption coefficient on the photon energy suggests the presence of a direct allowed interband transition whereE _g ^d =2·225 eV at room temperature, as well as indirect phonon-assisted transition. The absorption coefficient follows Urbach's empirical relation in the range 2·08–2·34 eV near the intrinsic edge, and a Gaussian shape was obtained near the band maximum. This behaviour is indicative of its excitonic origin and may be contributed to localized excitons in the crystal.     

Second Harmonic Generation in TlInS2 Crystals

The temperature dependence of the generation of the second optical harmonic in TlInS₂ crystals in the vicinity of the phase transitions high–temperature–incommensurate–polar phases is investigated. It is shown that radiation in the incommensurate phase occurs only when the fundamental wave propagates along the axis of the superstructure of a crystal and the presence of radiation for certain geometries of the experiment confirms the symmetry group C ₂ ³ of the low–temperature polar phase. The dependence of the spectra on the periodic temperature change is attributed to the occurrence of long–lived metastable states.     

Maximum light sums storage and differences in the luminescent characteristics of zinc sulfide single crystals,powders, and films

A comparative investigation is carried out of thermoluminescence, temperature dependence of luminescence, and damping of luminescence in zinc sulfide single crystals, powders, and films activated with silver orcopper, andnonactivated. Pulverized single crystals are also investigated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 37–42, July, 1981.