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Photoconductivity and its relaxation in Cu 1− x Zn x In 2 S 4 alloys ( x =0–16) single crystals were investigated in the temperature range 30–100 K. The long-lasting relaxation processes ( τ ~10 3 s) and induced photoconductivity phenomena were identified. The main parameters characterizing the photoconductivity kinetic were determined. The observed phenomena were analyzed by taking into account effects of the trapping levels. It is shown that relaxation of the photoconductivity and induced photoconductivity are controlled by the multicenter recombination in which both 'fast' and 'slow' recombination centers take part. [ABSTRACT FROM AUTHOR]

Temperature dependence of the electrical conductivity of CuInS 2 –ZnIn 2 S 4 and CuInSe 2 –ZnIn 2 Se 4 solid solutions possessing n-type conductivity has been studied. It has been established that when the temperature decreases down to ~100 to 27 K, the hopping mechanism of electrical conductivity with a variable jumping length between localized states positioned in a narrow energy band near the Fermi level becomes dominant. The main parameters of the hopping conductivity have been determined. At higher temperatures (150–300 K), in the CuInSe 2 –ZnIn 2 Se 4 single crystals containing 15 and 20 mol% ZnIn 2 Se 4 the thermally activated conductivity with activation energy of 0.018 and 0.04 eV, respectively, is detected. Among the CuInSe 2 –ZnIn 2 Se 4 single crystals, samples with 5 and 10 mol% ZnIn 2 Se 4 were found to be close to degenerate semiconductors. Temperature dependences of the electrical conductivity of CuInS 2 –ZnIn 2 S 4 single crystals are described by a more complicated function that may indicate a competition of several conduction mechanisms in these compounds. For the CuInS 2 –ZnIn 2 S 4 solid solutions, X-ray photoelectron core-level and valence-band spectra have been measured for both pristine and Ar + ion-bombarded surfaces. Our results indicate that the Cu 1− x Zn x InS 2 single-crystal surfaces are sensitive to Ar + ion-bombardment. Additionally, for the Cu 1 −x Zn x InS 2 crystal with the highest ZnIn 2 S 4 content, namely 12 mol% ZnIn 2 S 4 , the X-ray emission bands representing the energy distribution of the Cu 3d, Zn 3d and S 3p states have been measured and compared on a common energy scale with the X-ray photoelectron valence-band spectrum. [ABSTRACT FROM AUTHOR]

CuInSe 2 –ZnIn 2 Se 4 n -type semiconductor crystals were grown by the horizontal variant of the Bridgman method. Their band gap was estimated from the position of the intrinsic absorption band edge. The obtained values of the band gap vary monotonically with the composition of the compounds: at 300 K they increased from 1 eV up to 1.08 eV with increasing amount of ZnIn 2 Se 4 in the range of 5–20 mol%. The solid solutions containing 5–10 mol% ZnIn 2 Se 4 had demonstrated weak temperature dependence of the electrical conductivity, high electron density and low photoconductivity. This evidences their nearly degenerate state. In the crystals with 15 and 20 mol% ZnIn 2 Se 4 a variable range hopping conduction mechanism was found to dominate in the range ∼30–110 K and a thermally activated conductivity at T ⩾ 130 K was observed. The determined values of the donor activation energy for the samples with 15 and 20 mol% ZnIn 2 Se 4 were 0.018 eV and 0.04 eV, respectively. The characteristic feature of the spectral distribution of their photoconductivity at 30–70 K is presence of a narrow peak at 1160–1190 nm. [ABSTRACT FROM AUTHOR]

Abstract: Copper indium disulfide–zinc indium tetrasulfide solid solutions with different contents of zinc indium tetrasulfide, ranging from 4 to 16mol% were grown by the horizontal modification of the Bridgman–Stockbarger method. Their structural properties were investigated by the X-ray analysis. Spectral dependences of their photoconductivity were analyzed at T≈30K. In the single crystals with 8–12mol% of zinc indium tetrasulfide the induced photoconduction phenomenon was observed. It could be explained by the model of three recombination and trapping centers with different capture cross sections. Indium vacancies VIn or substitutional defects CuIn are possibly the fast recombination centers; meanwhile copper vacancies VCu act as the slow recombination centers. The presence of electrically active shallow defects was confirmed by the measurements of the temperature dependences of electrical conductivity and thermally stimulated currents of these samples with n-type conductivity. [Copyright &y& Elsevier]

Highlights: [•] High-quality Ag2HgSnS4 single crystal has been synthesized. [•] Electronic structure of Ag2HgSnS4 has been studied by XPS and XES. [•] XPS data reveal low hygroscopicity of Ag2HgSnS4 surface. [•] Ag 4d states contribute predominantly in the central portion of the valence band. [•] S 3p states contribute mainly in the central and upper portions of the valence band. [ABSTRACT FROM AUTHOR]

Abstract: We have investigated CuInS2–ZnIn2S4 solid alloys containing 4, 8, and 12mol% ZnIn2S4. The samples with 16mol% ZnIn2S4 were two component ones. The materials were prepared by the liquid phase deposition method, and had demonstrated n-type conductivity. Temperature dependencies of their electrical conductivity and thermally stimulated currents were investigated in the temperature region from 27K to 300K. Their photoconductivity spectral distributions of were analysed at T≈30K. In the crystals with 8–12mol% of ZnIn2S4 the induced photoconductivity phenomenon was observed. It was explained on the basis of the two trapping centre model. In the low temperature region conductivity behaviour could be explained on the basis of the Variable Range Hopping model. [Copyright &y& Elsevier]

Abstract: X-ray photoelectron core-level and valence-band spectra for pristine and Ar+-ion irradiated (001) surfaces of AgCd2GaS4 and AgCd2GaSe4 single crystals grown, respectively, by the Bridgman method and the method of direct crystallization have been measured in the present work. The X-ray photoelectron spectroscopy (XPS) results reveal high chemical stability of (001) surfaces of AgCd2GaS4 and AgCd2GaSe4 single crystals. Electronic structure of AgCd2GaS4 has been calculated employing the full potential linearized augmented plane wave method. For the AgCd2GaS4 compound, the X-ray emission bands representing the energy distribution of the valence Ag d-, Cd d-, Ga p- and S p-like states were recorded and compared on a common energy scale with the XPS valence-band spectrum. The theoretical and experimental data regarding the occupation of the valence band of AgCd2GaS4 were found to be in excellent agreement to each other. Second harmonic generation (SHG) efficiency of AgCd2GaS4 by using the 320ns CO laser at 5.5μm has been recorded within the temperature range 80–300K. Substantial increase of the photoinduced SHG which in turn is substantially dependent on the temperature has been detected for the AgCd2GaS4 compound. [Copyright &y& Elsevier]

Abstract: Single crystals of the quaternary phase AgCd2GaSe4 were grown using the method of directed crystallization. Their physical properties were studied. Studying the temperature dependence of electrical conductivity an impurity defect band with activation energy of ∼0.30eV in the upper half of the energy band gap was identified. Based on the analysis of the spectral dependence of the absorption coefficient, the width of the energy gap of the crystals was estimated ∼1.7eV at T=293K. At the edge of the intrinsic absorption band this dependence could be approximated by the Urbach rule with the characteristic disorder parameter Δ 0∼0.079eV. Based on this value, concentration of the point defects responsible for the absorption edge blurring was determined to be ∼1.4×1020 cm−3. [Copyright &y& Elsevier]

Abstract: The phase equilibria in the quasi-ternary system Ag2S–HgS–SnS2 at 298K were investigated using X-ray diffraction. The existence of the Ag2HgSnS4 compound that is the only one at this temperature was confirmed. The vertical section Ag8SnS6–HgS was constructed. It is of the eutectic type (eutectic point coordinates are 89mol% HgS and 881K), with the formation of a HT–Ag8SnS6 solid solution range extending to ∼57mol% HgS at 881K. The Ag2HgSnS4 crystal structure was refined using X-ray powder diffraction. Ag2HgSnS4 crystallizes in the orthorhombic space group Pmn21 (ST Cu2CdGeS4) with unit cell parameters a =0.82074(4)nm, b =0.70330(3)nm and c =0.67180(3)nm. The atomic parameters were refined in the isotropic approximation to R =0.0795. Ag2HgSnS4 single crystals (Ø =10–12mm; l =30mm) were grown using the Bridgman–Stockbarger technique. The single crystals exhibit n-type semiconductor conductivity. The photoconductivity spectra at liquid nitrogen and room temperatures were investigated, and their non-elementary nature was shown. [Copyright &y& Elsevier]

Abstract: Single crystals of the quaternary single crystals Ag2CdSnS4 were grown for the first time using the horizontal gradient freeze technique. Optical spectral and photoelectric properties of obtained crystals were investigated. The band gap energy at 77K according to the photoconductivity spectra is 1.94eV. The energy levels of the major donor centers in the band gap were determined. The role of intrinsic defects in the observed dependences is analyzed. The energy levels of the major donor centers in the band gap were determined. A small photoconductivity maximum at low temperature is observed at wavelength λm =640nm (hν ∼1.94eV); situated in the fundamental absorption band, which unambiguously corresponds to the intrinsic origin of photoconductivity. The increase of the extrinsic photoconductivity with the maximum at λm ∼800nm with temperature leads to its domination above 240K. The observed peculiarity can be explained by the photoexcitation of electrons from the valence band to the donor centers which are empty at high temperatures and with further thermal excitation to the conduction band. [Copyright &y& Elsevier]