Optical Properties of MnIn2S2Se2 Single Crystals

Optical transmittance and reflectance spectra of MnIn₂S₂Se₂ single crystals are measured in the wavelength range from 0.5 to 30 μm. The interference method is used to determine the refractive index of the compound for wavelengths between 0.8 and 12 μm. From an analysis of the absorption spectrum it follows that the fundamental edge is due to forbidden indirect transitions between parabolic bands for the polarization E ⊥ c with a gap energy of 1.50 eV at room temperature.     

Optical Properties of Bi2Se3‐xAsx Single Crystals

Bi₂Se_3‐xAs_x single crystals with the As content of c_As = 0 to 2.0x10¹⁹ atoms/cm³ prepared from the elements of 5N purity by means of a modified Bridgman method were characterized by measurements of infrared reflectance and transmittance. Values of the plasma resonance frequency omega_p, optical relaxation time tau, and high‐frequency permittivity were determined by fitting the Drude‐Zener formulas to the reflectance spectra. It was found that the substitution of As atoms for Se atoms in the Bi₂Se₃ crystal lattice leads to a decrease in the omega_p values. This effect is accounted for by a model of point defects in the crystal lattice of Bi₂Se_3‐xAs_x. The dependences of the absorption coefficient K on the energy of incident photons were determined from the transmittance spectra. The optical width of the energy gap is found to decrease with increasing As content. The values of the exponent b from the relation of K ∼ lamda^b for the long‐wavelength absorption edge range within the interval 2.0 to 2.3, i.e. the dominant scattering mechanism of free current carriers in Bi₂Se_3‐xAs_x crystals is the scattering by acoustic phonons.     

Crystal Structure and Some Physical Properties of CuGaIn2Se5

Crystallography Reports - Polycrystals of CuGaIn2Se5 solid solution have been synthesized for the first time. X-ray diffraction analysis revealed that the sample studied is crystallized in the...     

Transport Properties of TlInSe2 Single Crystals

Single crystals of TlInSe₂ were prepared by a special modified Bridgman technique. The influence of temperature on the electrical conductivity, Hall effect, Hall mobility, and the carrier concentration was investigated in the temperature range 190–625 K. The energy gap of conduction was calculated. The scattering mechanism of the charge carrier was discussed in the same temperature range. Beside this, the thermoelectric power was measured in a temperature range extending from 190 up to 485 K.     

Electrical and Photoelectrical Properties of n-CuInS2 Single Crystals

The temperature dependences of free electron density and mobility in n-CuInS₂ single crystals have been determined from the Hall effect measurements. The ionization energy of donors and their densities have been estimated. The results of measurements show that the crystals are strongly compensated. The spectral distribution of photoconductivity, the dependence of photoconductivity on excitation intensity, and the photoconductivity decay with time have been measured in the n-CuInS₂ crystals at different temperatures. The results of photo-conductivity measurements suggest linear recombination of photo-electrons at weak excitation and quadratic recombination at high excitation intensity. The compensated deep acceptor probably acts as the recombination centre.     

Semiconducting Properties of TI2Te3 Single Crystals

Electrical conductivity and Hall effect measurements were performed on single crystals of TI₂Te₃ to have the general semiconducting behaviour of this compound. The measurements were done at the temperature range 160–350 K. All crystals were found to be of p-type conductivity. The values of the Hall coefficient and the electrical conductivity at room temperature were 1.59 × 10³ cm³/coul and 3.2 × 10⁻² ω⁻¹ cm⁻¹, respectively. The hole concentration at the same temperature was driven as 39.31 × 10¹¹ cm⁻³. The energy gap was found to be 0.7 eV where the depth of impurity centers was 0.45 eV. The temperature dependence of the mobility is discussed.     

Transport Coefficients of (Bi1-xSbx)2Se3 Single Crystals

(Bi_1-xSb_x)₂Se₃(x = 0.0 to 0.2) single crystals were prepared using a modified Bridgman method. Measurements of the Hall coefficient R_H, electrical conductivity σ and Seebeck coefficient α showed that incorporation of the antimony atoms into the Bi₂Se₃ crystal lattice results in an increase in the free electron concentration for a low antimony content, whereas the free electron concentration is suppressed in the range of a high antimony content. This effect is explained qualitatively by changes in the concentrations of point defects in the (Bi_1-xSb_x)₂Se₃ crystals. We asume that the substitution of Bi atoms by Sb atoms results in a decrease in the concentration of Se vacancies V and antisite defects Bí_Se. The course of the dependences of In (R_Hσ) vs In T manifests that in the temperature region of 100–400 K transport properties of the studied crystals are characterized by a mixed transport mechanism of free carriers, mainly on acoustical phonons and ionized impurities.     

La3Ga5SiO14单晶的生长、性能及SAW应用

本文综述了新型压电晶体La3Ga5SiO14的最新研究进展,详细讨论了该晶体的生长问题,简单介绍了该晶体的性能及其在SAW和BAW方面的应用,分析了该晶体在压电应用方面的优势.     

Growth and Characterization of CdAl2S4 and CdAl2Se4 Single Crystals

Single crystals of CdAl₂S₄ and CdAl₂Se₄ showing high transparency were grown by the chemical vapour transport method. Their composition was proven by microprobe analysis. Structural investigations were done by Rietveld refinements and are in good agreement with known structure data. From transmittance and reflectance measurements the energy of the band gap WBS estimated. Assuming a direct nature of the corresponding optical transition the following values were obtained: E_g = 3.82 eV (RT), E_g = 3.94 eV (85 K) for CdAl₂S₄ and E_g = 2.95 eV (RT), E_g = 3.07 eV (85 K) for CdAl₂Se₄ respectively.     

Electrical Properties of CuInSe2 Single Crystals Implanted with Xenon

Both p-type and n-type CuInSe₂ single crystals were implanted with 40 keV ¹³⁰Xe⁺ ions up to doses of 5 · 10¹⁶ cm⁻². Implanted layers on p-type substrates showed an initial increase of the resistivity followed by a continuous decrease of the resistivity at higher doses. Implanted layers on n-type substrates gave also an increase of the resistivity at lower doses, but at higher doses a conductivity type conversion from n-type to p-type took place, followed by a decrease of the resistivity. To explain the experimental results it is supposed that the increase of the resistivity is mainly due to charge carrier scattering at extended defects while the decrease of the resistivity at high doses is due to the predominant creation of intrinsic acceptor states during implantation.     

Optical Properties of Pb-Doped Bi2Te3 Single Crystals

The reflectance and the transmittance spectra in the IR region were measured on Pb-doped Bi₂Te₃ single crystal samples grown by a modified Bridgman technique. The plasma resonance frequency, the optical relaxation time, and the high-frequency permittivity were determined by fitting the Drude-Zener formulas to the reflectance spectra. It was found that Pb impurities in Bi₂Te₃ behave as acceptors. A part of incorporated Pb atoms behaves as electrically inactive. This effect is explained as due to the fact that electrically active Pb-atoms form substitutional defects, Pb′_Bi, and the others form inactive two-dimensional defects — seven-layer lamellae Te—Bi—Te—Pb—Te—Bi—Te. The transmittance spectra were used for the determination of the dependence of the absorption coefficient K on the energy of incident photons. The optical width of the energy gap increases with increasing Pb content. The values of the exponent α from the relation of K ∼ λ^α for the long-wavelength absorption edge range within the interval of 1.6 to 2.8, i.e. the dominant scattering mechanism of free current carriers in Pb-doped Bi₂Te₃ crystals is the scattering by acoustic phonons. By comparison of the effect of doping atoms of the IV.B group of the periodic table on the concentration of holes in Bi₂Te₃ crystal lattice was concluded that the tendency to form substitutional defects Me′_Bi (Me = Ge, Sn, Pb) in these crystals increases from Ge to Pb, whereas the tendency to the formation of seven-layer lamellae Te—Bi—Te—Me—Te—Bi—Te decreases.     

Photoluminescence Spectra of GaS0.75Se0.25 Layered Single Crystals

Photoluminescence (PL) spectra of GaS_0.75Se_0.25 layered single crystals have been studied in the wavelength region of 500‐850 nm and in the temperature range of 10‐200 K. Two PL bands centered at 527 ( 2.353 eV, A‐band) and 658 nm (1.884 eV, B‐band) were observed at T = 10 K. Variations of both bands have been studied as a function of excitation laser intensity in the range from 8 × 10^‐3 to 10.7 W cm^‐2. These bands are attributed to recombination of charge carriers through donor‐acceptor pairs located in the band gap. Radiative transitions from shallow donor levels located 0.043 and 0.064 eV below the bottom of conduction band to acceptor levels located 0.088 and 0.536 eV above the top of the valence band are suggested to be responsible for the observed A‐ and B‐bands in the PL spectra, respectively.     

AgGa0.7In0.3Se2晶体热膨胀行为研究

采用一种新的定向方法,快速定出了AgGa0.7In03Se2晶体c轴方向,制备得到[001]、[100]方向的块状样品;采用德国B(a)hr公司的WinTA 100热膨胀仪对其进行测试,分别获得了晶体沿c轴、a轴方向的热膨胀系数,分析了它们随温度变化的规律以及晶体出现反常热膨胀的机制;计算出晶体的体热膨胀系数和各向异性因子,分析讨论了晶体非轴向热膨胀系数在不同温度下随cos2φ的变化规律.     

Preparation and Properties of YIG Single Crystals

In this paper a summary is given on the reproducible preparation of large, nearly defectless yttrium iron garnet single crystals (YIG) grown in fluxes by slowly cooling with accelerated crucible rotation (ACRT) and local bottom cooling. The surface morphology of the growth faces is discussed with regard to the growth mechanism. By different methods the crystals are characterized regarding their lattice defects (impurities, growth striations, dislocations, inclusions). Ferromagnetic resonance measurements in the X-band at polished, inclusionsfree discs show that the linewidth ΔH of any crystals from different runs are less than 0.45 Oe.     

Carrier Transport Properties of InS Single Crystals

The electrical resistivity and Hall effect of indium sulfide single crystals are measured in the temperature range from 25 to 350 K. The donor energy levels located at 500, 40 and 10 meV below the conduction band are identified from both measurements. The data analysis of the temperature‐dependent Hall effect measurements revealed a carrier effective mass of 0.95 m₀, a carrier compensation ratio of 0.9 and an acoustic deformation potential of 6 eV. The Hall mobility data are analyzed assuming the carrier scattering by acoustic and polar optical phonons, and ionized impurities.     

Electronic Transport Properties of Thallium Sesquiselenide Single Crystals

Electronic transport measurements were made on single crystal samples of Tl₂Se₃. The crystals were prepared by a special design based on Bridgman technique. The influence of temperature on the electrical conductivity, Hall effect, Hall mobility and the carrier concentration was investigated in the temperature range 200–400 K. The energy gap as well as the ionization energy were calculated. The scattering mechanism of the charge carrier was discussed in the same temperature range.     

Low-temperature Magnetic Properties of Terbium Orthoferrite Single Crystals

Spontaneous and by an external magnetic field induced magnetic phase transitions in TbFeO₃ have been experimentally studied. Precision investigations of velocities of transmission and attenuation of sound wave were made, the processes of formation and rearrangement of magnetic structure examined and its change under the influence of external magnetic field explored. This has been made possible by the development of methods of controlled growth of rare-earth orthoferrites resulting in the formation of high-quality single crystals of required size with reproducible physical properties. The measurements were taken in the temperature range from 0.45 to 8.0 K. From the threshold Geld values a H_a  T phase diagram for TbFeO₃ has been plotted.