Charge transport and mechanisms of electron scattering in (HgSe)3(In2Se3) crystals doped with 3d transition metals

We have studied the transport properties of (HgSe)₃(In₂Se₃), (HgSe)₃(In₂Se₃)〈Mn〉, and (HgSe)₃(In₂Se₃)〈Fe〉 crystals and identified the predominant mechanisms of electron scattering in them. The transport properties of the (HgSe)₃(In₂Se₃) crystals, undoped and doped with 3d transition metals, have been studied by the four-probe technique. The results demonstrate that the Hall coefficient of the crystals is temperature-independent, their electrical conductivity shows metallic behavior and is an almost linear function of temperature, and their thermoelectric power increases with increasing temperature.     

The bulk properties of the Na2SO4-H2O system in a wide range of the parameters of state

The constant-volume piezometer method is used to determine the density of aqueous solutions of sodium sulfate in the temperature range from 291 to 573 K and in the ranges of pressures from 2 to 40 MPa and concentrations from 0.088 to 1.116 mol/kg H₂O. In view of the available literature data, an equation is constructed describing the specific volumes of solution. Limiting partial molar volumes of electrolyte are calculated.     

Effects of Na on the properties of Cu(In,Ga)S2 solar cells

We have prepared Cu(In,Ga)S₂ solar cells with changing Na concentration using several preparation methods. We have investigated the hole density and solar cell properties. The hole density increases with increasing Na concentration up to 10¹⁷ cm^− 3, and stays almost constant for higher concentrations. It can be considered that Na might passivate a single type of donor up to 10¹⁷ cm^− 3. For all preparation methods, the efficiencies of solar cells prepared with the Cu(In,Ga)S₂ thin films increase with increasing Na concentration. We propose a Na diffusion model derived from depth profiles obtained for each of the preparation methods.     

Magnetic properties of heterogeneous (FeNi)-Ag films in a wide composition range

The preparation of a series of granular films (Fe₂₀Ni₈₀)_xAg_100−x (5?x?95, x is the vol.%) of 200 nm thickness on mica substrates by electron beam evaporation technique is described. Structural and magnetic investigations are made by X-ray diffraction, magnetoresistive and ferromagnetic resonance techniques. The isotropic giant magnetoresistance effect as high as 6% in magnetic field of 8.2 kOe at room temperature and 13% at liquid nitrogen temperature is observed.     

Direct synthesis of CuIn(Sex, S1 − x)2 films from elemental In, Cu, Se, S particle precursor films and its dependence on energy

CuIn(Se_x, S_1 − x)₂ films were prepared by means of non-vacuum, instantaneous, direct synthesis from elemental In, Cu, Se and S particle precursor films by passing an electrical current with precise control through the metal substrate. For a constant reaction period of 1 s, unreacted elemental particles remained in the films for powers below 1 kV A, whereas the reaction to CuIn(Se_x, S_1 − x)₂ (x = 1) appeared to be complete at higher power. Chalcopyrite structure was observed in the range from 1.08 kV A to 1.24 kV A, the sphalerite structure appeared over 1.35 kV A. X-ray diffraction shows single (112) peaks of CuIn(Se_x, S_1 − x)₂ and the peak position agreed with the nominal composition of the precursors.     

Flash analog-to-digital converter operational in an ultra wide temperature range (room temperature to 4.2 K) in standard CMOS technology using a cryogenic reset switching scheme

This work presents the design and test result of a standard 0.7 μm CMOS flash analog-to-digital converter (ADC) operational in an ultra wide temperature range (UWT, room temperature down to 4.2 K). To maintain the circuit’s performance over the UWT range in the presence of temperature induced transistor anomalies, dedicated topology and switching schemes are utilized. Test results mentioned in this text are from a single process run, no design iterations were made.     

Room temperature multiferroic properties of (Bi0.95La0.05)(Fe0.97Mn0.03)O3/NiFe2O4 double layered thin film

(Bi_0.95La_0.05)(Fe_0.97Mn_0.03)O₃/NiFe₂O₄ double layered thin film was prepared on a Pt(111)/Ti/SiO₂/Si(100) substrate by a chemical solution deposition method. X-ray diffraction and Raman scattering spectroscopy studies confirmed the formation of the distorted rhombohedral perovskite and the inverse spinel cubic structures for the (Bi_0.95La_0.05)(Fe_0.97Mn_0.03)O₃/NiFe₂O₄ double layered thin film. The (Bi_0.95La_0.05)(Fe_0.97Mn_0.03)O₃/NiFe₂O₄ double layered thin film exhibited well saturated ferromagnetic (2 M_r of 18.1 emu/cm³ and 2H_c of 0.32 kOe at 20 kOe) and ferroelectric (2P_r of 60 μC/cm² and 2E_c of 813 kV/cm at 866 kV/cm) hysteresis loops with low order of leakage current density (4.5 × 10⁻⁶ A/cm² at an applied electric field of 100 kV/cm), which suggest the ferroelectric and ferromagnetic multi-layers applications in real devices.     

Two Gaussian distributions of the barrier height in chemical vapor deposition diamond/silicon junctions over a wide temperature range

Analysis of the current-voltage characteristics of a chemical vapor deposition diamond/n⁺-Si junction for the temperature range 120-400 K revealed atypical temperature dependence for both the barrier height and the ideality factor and non-linearity in the Richardson plot at low temperatures. These results were interpreted according to model of Chand and Kumar. The junction revealed the existence of two Gaussian distributions of the barrier height, with mean barrier heights of 0.88 and 1.12 eV and standard deviations of 0.098 and 0.132 eV and Richardson constant of 0.5 × 10⁶ and 0.9 × 10⁶ A m⁻² K⁻² for the temperature intervals 120-200 and 200-400 K, respectively. The polycrystalline diamond matrix is composed of two distinct phases of microcrystals and amorphous carbon and each Gaussian distribution was related to one of these phases.     

Thin film preparation and characterization of wide band gap Cu3TaQ4 (Q = S or Se) p-type semiconductors

The structural, optical, and electronic properties of thin films of a family of wide band gap (E_g > 2.3 eV) p-type semiconductors Cu₃TaQ₄ (Q = S or Se) are presented. Thin films prepared by pulsed laser deposition of ceramic Cu₃TaQ₄ targets and ex-situ annealing of the as-deposited films in chalcogenide vapor exhibit mixed polycrystalline/[100]-directed growth on amorphous SiO₂ substrates and strong (100) preferential orientation on single-crystal yttria-stabilized zirconia substrates. Cu₃TaS₄ (E_g = 2.70 eV) thin films are transparent over the entire visible spectrum while Cu₃TaSe₄ (E_g = 2.35 eV) thin films show some absorption in the blue. Thin film solid solutions of Cu₃TaSe_4 − xS_x and Cu₃TaSe_4 − xTe_x can be prepared by annealing Cu₃TaSe₄ films in a mixed chalcogenide vapor. Powders and thin films of Cu₃TaS₄ exhibit visible photoluminescence when illuminated by UV light.     

溶胶-凝胶技术制备(Bi4-x,Lax)Ti3O12陶瓷的工艺技术研究

采用3种溶胶－凝胶（sol-gel）工艺,以硝酸铋、硝酸镧和钛酸丁酯为原料,制备掺镧钛酸铋（Bi4-x,Lax)Ti3O12（简记为BLT）陶瓷。通过控制溶胶－凝胶工艺,分析比较不同溶胶－凝胶过程对陶瓷结构的影响,为后续BLT铁电薄膜的溶胶－凝胶制备选择最佳工艺技术条件。研究发现采用滴定方式的sol-gel工艺制备的陶瓷具有较好的取向和结构。     

Thermal conductivity and electrical resistivity of cadmium arsenide (Cd3As2) in the temperature range 4.2–40 K

Results on electrical resistivity and thermal conductivity measured in the temperature range 4.2–40 K are presented for single-crystal and polycrystalline samples of Cd₃As₂. Hall effect has been studied at temperatures of 4.2, 77, and 300 K. The calculated value of the conduction electron concentration was in the range 1.87–1.95 10²⁴m^–3. Electrical resistivity of all investigated samples was independent of temperature up to about 10K and increased slowsly at higher temperatures. The thermal conductivity shows a maximum in the region in which the lattice component of thermal conductivity dominates. The strong anisotropy of the lattice component determines the anisotropy of the total thermal conductivity. The electronic component of thermal conductivity does not exhibit any anisotropy and shows a maximum at a temperature of about 300 K.Paper submitted to the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Lithium disorder in the vicinity of the superionic phase transition in monoclinic and rhombohedral Li3In2(PO4)3

Rhombohedral and monoclinic modifications of the Li₃In₂(PO₄)₃ compound have been studied by X-ray diffraction, infrared (i.r.) analysis, Raman light scattering, differential thermal analysis (DTA), differential scanning calorimetry (DSC) and impedance spectroscopy, in a wide temperature range of 290–600 K. Analysis of the data allows the suggestion that the superionic phase transition, observed in these materials in the temperature interval 370–385 K, belongs to Faraday type phase transformations. PO₄ tetrahedra, which are a partition of the (In₂P₃O₁₂) ₃₀₀ ^3– rigid skeleton, have been found deformed. This seems to be due to an ordered lithium ion-vacancy distribution in the low temperature, non-superionic, polymorphs. With increasing temperature these deformations disappear. This disappearance can be caused by a decrease of the correlation length of the lithium ion-vacancy order.     

On the thermal expansion and crystallography of cubic (C) and monoclinic (B) forms of Gd2O3 in the temperature range 20 to 900°C

Thermal expansion coefficients of B-form (monoclinic) and C-form (cubic) Gd₂O₃ have been measured in the temperature range 20 to 900° C, by X-ray diffractometry. The thermal expansion coefficients of both cubic and monoclinic material are linear in the temperature range studied. The expansion of monoclinic material is, however, very anisotropic, and the minor axis of the thermal expansion ellipsoid is not parallel to the edge of the primitive cell to which Gd₂O₃ has been assigned. It is noted that the anisotropy in expansion behaviour of this material indicates that anisotropic growth probably occurs during irradiation.     

Incoherent-to-Coherent Conversion by Use of the Photorefractive Beam-Fanning Effect and Amplification by Two-Wave Coupling in a Photorefractive Ba(1-x)Sr(x)TiO(3) Crystal

Incoherent-to-coherent conversion by use of the photorefractive beam-fanning effect and amplification by two-wave coupling have been demonstrated experimentally in a photorefractive Ba(1-x)Sr(x)TiO(3) crystal. The converted coherent image is amplified by 60x. The resolution of the amplified coherent image is ~28 line pairs/mm. A notable advantage of the method is that incoherent-to-coherent conversion and coherence amplification of the converted coherent image are realized simultaneously in a photorefractive crystal.     

Influence of temperature on phase separation in the ternary systems [Th(NO3)4(TBP)2]-decane-third organic component

The phase diagrams of ternary systems [Th(NO₃)₄(TBP)₂]-decane-third organic component (n-butanol, n-octanol, isobutanol, dimethylhexanol, chloroform, carbon tetrachloride, o-dichlorobenzene, tri-n-butyl phosphate, o-xylene, toluene, and linear carboxylic acids) were studied in the temperature range 288.15–333.15 K. These diagrams contain the fields of homogeneous solutions and the field of separation into two liquid phases (I, II). Phase I is enriched in Th(NO₃)₄(TBP)₂ and third component and phase II is enriched in decane. The phase separation is not appreciably influenced by temperature. In phase separation, the third component is predominantly concentrated in phase I, in spite of the fact that the third component and decane have infinite mutual solubility at all the temperatures. The composition of the ternary systems in the critical point is dependent on the kind of the third component.     

The structure of electrical double layer of silica in the presence of polyvinyl alcohol (PVA) at different temperatures

The effect of polyvinyl alcohol (PVA) adsorption on the structure of the electrical double layer of silica (SiO₂) in the temperature range 15-35 °C was studied. The potentiometric titrations were applied in the experiments, which enable determination of the surface charge density of silica systems without and with adsorbed polymer. The preferential adsorption of acetate groups of not fully hydrolysed PVA chains (degree of hydrolysis 97.5%) through hydrogen bridges is mainly responsible for bonding process of polymer with adsorbent surface. The obtained results indicate that temperature increase causes more stretched conformation of adsorbed macromolecules and the greater number of acetate groups can be adsorbed on the solid surface. It leads to changes in structure of polymer adsorption layer on the solid surface and the increase of the SiO₂ surface charge with the rising temperature was observed.     

(Nd0.75Na0.25)1-x(Nd0.5Ca0.5)xMnO3中电荷有序稳定性关系的超声研究

系统研究了（Nd0.75Na0.25）1-x（Nd0.5Ca0.5）xMnO3（x=0、0．25、0．5、0．75、1）单相多晶样品在低温下的电磁输运性质和超声特性．电阻和磁化率的测量表明所有样品均发生了电荷有序相变．随着钠掺杂量的增加，电荷有序相变温度（Tco）向低温移动同时低温端磁化强度增大，并且电荷有序态趋向于不稳定和短程化．超声纵波声速从室温开始随着温度的降低逐渐减小，在Tco之后声速急剧硬化．这种超声异常表明体系中存在着强烈的电-声子相互作用，该电-声子耦合来源于Mn^3＋的Jahn-Teller效应．对纵波模量软化部分的拟合显示，随着钠的掺入，反映Jahn-Teller效应大小的Jahn-Teller耦合能EJT变小．分析认为电荷失配效应是导致电荷有序被抑制和Jahn-Teller耦合能EJT变小的主要因素．