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Abstract: Quaternary single crystals Ag x Ga x Ge1− x Se2 (x =0.333, 0.250, 0.200, and 0.167) have been grown by the two-zone Bridgman method. X-ray diffraction analysis has revealed that all the four compounds are crystallized in the noncentrosymmetric orthorhombic space group Fdd2. Position of constituent atoms in the unit cells of the Ag x Ga x Ge1− x Se2 single crystals have been determined. X-ray photoelectron core-level and valence-band spectra for pristine and Ar+ ion-irradiated surfaces of the single crystals under consideration have been measured. It has been established that the Ag x Ga x Ge1− x Se2 single crystals are very sensitive to Ar+ ion-irradiation. In particular, bombardment of the single-crystal surfaces with energy of 3.0keV during 5min at an ion current density of 14μA/cm2 has induced significant modification in top surface layers leading to complete elimination of Ag atoms in the layers. Furthermore, for all four Ag x Ga x Ge1− x Se2 single crystals, the charge states of Ag, Ga, and Ge atoms do not alter when varying the x value, whilst the negative charge of selenium atoms slightly decreases with decreasing x value. All the crystals show substantial photo induced changes of absorption under influence of 808nm 0.8Wcw laser. [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]

Highlights: [•] Two-photon absorption of TlInSnSe single crystals. [•] Maximal TPA was achieved for x =0.1. [•] Size enhancement of TPA was up to 4 times. [ABSTRACT FROM AUTHOR]

Abstract: The X-ray photoelectron core-level and valence-band spectra for pristine and Ar+-ion irradiated surfaces of a Tl3PbBr5 single crystal grown by the Bridgman–Stockbarger method have been measured. The present X-ray photoelectron spectroscopy (XPS) results reveal high chemical stability of Tl3PbBr5 single crystal surface. Total and partial densities of states of constituent atoms of low-temperature (LT) orthorhombic Tl3PbBr5 phase (space group P21212) have been calculated using the full potential linearized augmented plane wave (FP-LAPW) method. The FP-LAPW data reveal that contributions of the Br 4p-like states dominate in the valence band of LT-Tl3PbBr5; they contribute mainly into the top and the central portion of the valence band with also significant contributions throughout the whole valence-band region. The bottom of the valence band of LT-Tl3PbBr5 is composed mainly of the Tl 6s-like states, whilst the unoccupied Pb 6p- and Tl 6p-like states dominate at the bottom of the conduction band. We have explored the crystallochemistry and origin of the chemical bonds in Tl3PbBr5 with respect to the use as mid-IR non-linear optical crystals. Comparison of the spectral dependence to the second order susceptibilities for the titled crystals is performed with respect to the 3.39 μm illuminated crystals. Possibility of the use of Tl3PbBr5 crystals as IR operated non-linear optical crystals is discussed. [Copyright &y& Elsevier]

Highlights: [•] Electronic structure of Ag2CdSnS4 single crystal has been studied by XPS and XES. [•] Low hygroscopicity is characteristic of Ag2CdSnS4 single crystal surface. [•] Ag 4d states contribute mainly in the central portion of the valence band. [•] Cd 4d states contribute predominantly at the bottom of the valence band. [•] S 3p states contribute mainly in the central and upper portions of the valence band. [ABSTRACT FROM AUTHOR]

Highlights: [•] High-quality TlPb2Br5 single crystal has been synthesized. [•] XPS data reveal high chemical stability and low hygroscopicity of TlPb2Br5 surface. [•] Electronic structure of TlPb2Br5 is calculated by the FP-LAPW method. [•] The FP-LAPW results indicate that the TlPb2Br5 compound is an indirect-gap material. [ABSTRACT FROM AUTHOR]

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]

Abstract: Paper reports the piezooptical studies on langasit La3Ga5SiO14 (LGS) and calcium tungstate CaWO4 (CWO) crystals by means of the combined optical interferometry and polarization-optical techniques. Corresponding methodology is supplied by a set of derived equations suitable for the determination of the absolute piezooptical coefficients (POCs) in the crystals of trigonal or tetragonal symmetry. It is shown, that for the determination of all the eight absolute POCs πіm of trigonal LGS or tetragonal CWO crystals by means of polarization-optical technique one must perform additionally at least two optical interferometry measurements in certain experimental geometries. In most cases the combined study considerably improves an accuracy in the determination of the absolute POCs. Due to a large piezooptical effect revealed in CWO crystals they may be considered as quite perspective materials for eventual photoelastic or acoustooptical applications. [ABSTRACT FROM AUTHOR]