Optical and photoelectric properties of TlInS2 layered single crystals

Single crystals of the layered compound TlInS₂ were grown by direct synthesis of their constituents. The spectral and optical parameters have been determined using spectrophotometric measurements of transmittance and reflectance in the wavelength range 200–2500 nm. Absorption spectra of thin layers of TlInS₂ crystals are used to study the energy gap and the interband transitions of the compound in the energy region 2–2.4 eV. The dispersion curve of the refractive index shows an anomalous dispersion in the absorption region and a normal one in the transmitted region. The direct and indirect band gaps were determined to be 2.34 and 2.258 eV, respectively. Photoconductivity measurements at room temperature resolve the structure that can be identified with the optical transition.     

Growth,electrical conductivity and microindentation studies of CuInS2 single crystals

Summary Single crystals of copper indium disulfide (CuInS₂) have been grown by chemical-vapour transport technique (CVT) using iodine as the transporting agent. The obtained phase was checked by X-ray diffractometry and the presence of copper, indium and sulfur in the grown crystals was confirmed by Energy-Dispersive Spectrum Analysis (EDSA). The mechanical properties of the grown crystals were studied using microindentation analysis. Optical-transmission measurements were done to determine the energy gap of the grown crystals. The four-probe technique was used to measure the electrical properties of the grown crystals. The as-grown crystals were found to bep-type conducting and they were converted ton-type by suitable annealing treatment. The electrical parameters of bothn- andp-type crystals were measured.     

Effect of annealing on the photoelectric properties of single crystals of InSe

The effect of different heat-treatment regimes on recombination processes in n-In_1.03Se_0.97<0.5Zn> was studied by the method of square-wave modulation of light intensity, with subsequent analysis of the experimental data by the least squares method on a computer. The specimens were annealed at a temperature of 360–400°C in a vacuum [1] or Zn vapors [11] for different periods of time. They were then slowly cooled at a rate of 2 deg/min (A) or quenched (B). It was established the lifetime of the nonequilibrium carriers increases by nearly an order of magnitude in case IB, while the ratio of s- and r-centers remains nearly the same. In case IIA, _s decreases roughly by a factor of two, while in the best specimens it reaches 2.3·10^–5 sec. Annealing for 20 h in regime IA leads to a large increase (by about 25%) in the density of s-centers.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 61–64, November, 1990.     

Electrical, optical, and photoelectric properties of electron-irradiated indium-doped cadmium sulfide single crystals

The effect of irradiation by 1.2-MeV electrons to a dose Φ=2×10¹⁷ cm^?2 on the electrical, optical, and photoelectric properties of In-doped CdS single crystals was studied. The experimental data obtained permit one to conclude that irradiation initiates decomposition of the supersaturated In solution in CdS, with the indium atoms at the sites of the cation sublattice being expelled by cadmium interstitial atoms. New slow-recombination centers were observed to exist in the irradiated CdS: In samples, with the maxima of optical quenching of the photoconductivity lying in the region of $\lambda _{M_1 } = 0.75\mu m$ and $\lambda _{M_2 } = 1.03\mu m$ . It is suggested that the new recombination centers are related to complexes containing cadmium vacancies and indium atoms.     

Radiative recombination in iridium-doped silver bromide single crystals

The infrared emission spectrum of iridium-doped silver bromide results from a process that is competitive with the visible emission due to iodide centers in pure AgBr crystals. The emitting species is Ir³⁺, and experiments are described which help elucidate the nature of the radiative processes involved.     

Phonon properties of CoSb2 single crystals

The phonon properties of CoSb(2) have been investigated by Raman scattering spectroscopy and lattice dynamics calculations. Sixteen out of eighteen Raman active modes predicted by factor-group analysis are experimentally observed and assigned. The calculated and measured phonon energies at the Γ point are in very good agreement. The temperature dependence of the A(g) symmetry modes is well represented by phonon-phonon interactions without contribution from any other phonon or electron related interactions.     

Structural and galvanomagnetic properties of CuInS2 films

Thin copper-indium-disulphide films were prepared by thermal evaporation technique. X-ray diffraction analysis of the compound used for evaporation showed a tetragonal polycrystalline structure. Differential Thermal Analysis (DTA) of this compound showed two exothermic peaks at 585 and 632 °C. Thin films with thicknesses of 0.14 and 0.27 nm have a deposition rate 10 nm/min, while those with thicknesses of 0.54 and 0.56 nm have a deposition rate 48 nm/min. The obtained films have polycrystalline structure as shown from the electron diffraction study. A growth process was detected in the films by transmission electron microscopy as the film thickness increases. The surface topography was revealed by scanning electron microscopy. The variations of Hall mobility and carrier concentration with magnetic induction were studied. The resistivity-temperature relationship was investigated, from which the activation energies before and after annealing were found to be 0.2, 0.3 and 0.055 eV, respectively.     

Magnetic and resonance properties of LiCu2O2 single crystals

We study the structural, magnetic, and resonance properties of LiCu₂O₂ single crystals grown by the spontaneous crystallization method. The data are interpreted on the assumption that the crystalline structure of the grown single crystals is orthorhombic. Long-range antiferromagnetic order sets in at temperatures below 22.5 K, while above this temperature the dependence of the magnetic susceptibility has a shape characteristic of interacting antiferromagnetic Heisenberg chains. We hypothesize that long-range magnetic order sets in below 22.5 K through the destruction of the ideal ladder structure of LiCu₂O₂ because of partial redistribution of copper and lithium ions at the crystal lattice sites and because of the presence of other defects in the crystalline structure. Zh. éksp. Teor. Fiz. 113, 1866–1876 (May 1998)     

Magnetic and transport properties of UBi2 and USb2 single crystals

The thermoelectric power, S(T), of USb₂ and UBi₂, which are tetragonal, uniaxial antiferromagnets below T _N?=?202?K and 180.8?K, respectively, have been examined between 0.4?K and 300?K. The values of S(T), up to now known above 70?K for USb₂ and unknown for UBi₂, are positive along the a-axis for both compounds in the whole examined temperature range. The S(T) data for the c-axis (the easy magnetization axis) are positive near room temperature for USb₂ and UBi₂ but becomes negative below 120?K and 170?K, respectively, with two very deep minima in S(T) dependence for USb₂. In the latter compound the Fermi surface, known from literature, is composed of the only cylindrical sheets that are slightly corrugated and parallel to the c-axis. UBi₂, the Fermi surface of which is composed of one spherical and two cylindrical sheets, shows corresponding minima although less pronounced than those in USb₂. Having at disposal the highest purity single crystals in comparison to those for which the resistivity, ρ(T), has been reported in literature, the ρ(T) anisotropy was re-examined for these two systems. Magnon and phonon contributions to their total electrical resistivity have been determined and the critical fluctuation behaviour of the resistivity near T _N for both dipnictides has been analysed. Although the magnetic susceptibilities of UBi₂ and USb₂ reveal a similarity, their transport properties are significantly different due to the difference in the Fermi surface topology.     

Magnetic properties of La2CuO4 single crystals

Magnetic susceptibility x of La₂CuO₄ crystals have been measured with external magnetic field perpendicular to and within the c plane. A kind of ordering or condensation of the spin system with the spin direction parallel to the c axis has been found although it is difficult to consistently explain all of the observed behaviors. Even above the ordering temperature (⋍ 250K), uniaxial anisotropy of x has also been observed.     

Electrical properties of cadmium and zinc doped CuInS2

The electrical resistivity and mobility of Cd and Zn doped CuInS₂ single crystals grown by a Bridgman technique have been investigated. Crystals annealed in Cd or Zn vapor at high temperatures (～ 800°C) exhibit degenerate behaviour while those crystals annealed at more moderate temperatures (～650°C) show ionized impurity conduction with a shallow activation energy on the order of 0.004 eV. Resistivities as low as 0.15 Ω-cm and mobilities as high as 90 cm²/v-sec have been observed.     

The structure and mechanical properties of Fe2AlMn single crystals

The microstructure and mechanical properties of off-stoichiometric single-crystal Fe₂AlMn have been investigated. After casting, the alloy contained two sets of thermal antiphase boundaries, (a/4)?111? and (a/2)?100?, which are attributed to the fact that the compound solidifies into a bcc structure and subsequently orders to a B2 structure and then a L2₁ structure respectively upon further cooling. Crystals strained under tension at room temperature in air at 1s^?1 showed 6% elongation, whereas specimens strained at 1?×?10^?5?s^?1 showed no elongation, indicating that the compound is sensitive to the testing environment. Fracture occurred on {100} in both cases. Compression tests showed that a yield anomaly was present at intermediate temperatures, with the peak yield strength occurring at about 800?K, which is slightly below the L2₁–B2 transition temperature of 898?K. The slip systems were found to be ?111?{110} at room temperature and 800?K. Transmission electron microscopy observations showed fourfold-dissociated ?111? dislocations in specimens strained at room temperature but only paired ?111? dislocations in specimens strained at the peak temperature. The room-temperature yield strength of quenched specimens increased with increasing quench temperatures from 700 to 1100?K.     

Mechanical properties of ZnSe : Cr2+ single crystals

The microhardness of single-crystal samples of ZnSe: Cr²⁺ with a chromium concentration in the range from 3.3 × 10¹⁷ to 4.0 × 10¹⁹ cm^?3 has been studied. The microhardness as a function of the load on the indenter on the faces (111), (1 $\bar 1$ 0), and (001) of the ZnSe: Cr²⁺ and ZnSe samples has been measured. It has been established that doping of zinc selenide with chromium leads to a decrease in the anisotropy of the mechanical properties and stabilization of the cubic sphalerite structure.