The semi-conducting properties of CdSnAs2

The paper gives the results of measuring the temperature dependence of the electrical conductivity(T), the Hall coefficientR _H (T) and the magnetic susceptibility(T) forn-type CdSnAs₂. The effective mass of the electrons was determined by analysis of the measured dependences on the basis of the simple theory for an isotropic non-degenerate semi-conductor. It was found to bem _n /m ₀=2×10^–2 in the intrinsic region and does not depend on the temperature; the energy gap ise _g ⁰=0·26 eV and the molar susceptibility of the CdSnAs₂ lattice _G ^mol=–112× ×10^–6. The mobility of the electrons in the intrinsic region reaches a value of _n =25 000 cm²V^–1sec^–1 at 500°K and decreases exponentially _n T ^–1.67 with rising temperature. The density of CdSnAs₂ was determined pyknometrically,g9=5·35 g cm^–3. The measurements were made on ann-type polycrystalline sample consisting of crystals a few millimetres in diameter, which at a temperature of 100°K had a free electron concentration ofn _s =6×10¹⁶ cm^–3.

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CdSnAs₂

(T), R _H (T) (T) CdSnAs₂ . m _n /m ₀= =2.10^–2, ; E _G ⁰=0,26 eV, CdSnAs_{2 G} ^mol= =–112.10^–6. 500°K _n =25 000 cm²V^–1sec^–1 , _n T ^–1,67. CdSnAs₂ =5,35 g cm^–3. , , 100°K n _s =6.10¹⁶cm^–3.

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The authors would like to thank Mr. P. Jansa for help in measuring the temperature dependence of the magnetic susceptibility.     

Energy band structure of CdSnAs2 and CdGeAs2

The energy band structure of CdSnA₂ and CdGeAs₂2 is calculated by the empirical-pseudopotential method, taking account of spin-orbital interaction. The calculated parameters – E_g = 0.25, _cr = 0.05, _s.o = 0.44 for CdSnAs₂ and E_g = 0.55, _cr = 0.20, and _s.o = 0.33 for CdGeAs₂ (all in eV) — are in good agreement with experiment. The conclusion drawn in a series of experimental works that there are additional minima close to the bottom of the CdSnAs₂ conduction band is not confirmed in the calculation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 78–82, December, 1981.     

Theory of the quantum yield in CdSnAs2

No-phonon ionization by collision in CdSnAs₂ is analyzed with an account of the second conduction band. This second band leads to an additional break in the quantum-yield band. Transition probabilities are calculated for these electron-electron collisions under very simple assumptions.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 11, pp. 39–43, November, 1969.     

The behavior of copper impurity in CdSnAs2

Single crystals of n-type CdSnAs₂ with a carrier concentration of 2 ·10¹⁷–4 ·10¹⁸ cm^–3 and mobility (3 to 6) · 10³ cm²/V ·sec were copper doped by diffusion saturation at temperatures from 400 to 570C. As a result of the study of the electrical properties of the doped crystals it was established that the copper in CdSnAs₂ is a fast-diffusing acceptor impurity. The solubility of Cu depends primarily on the donor-center concentration and has clearly a retrograde character. Low-temperature heat treatment (over the 200–400C range) of the Cu-doped specimens results in an increase in the acceptor concentration. The form of the log R(10³/T) curve indicates the existence of acceptor centers with an ionization energy of 0.05 eV in the Cu-doped CdSnAs₂ specimens.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 16, No. 7, pp. 39–44, July, 1973.     

Effect of polarity on properties of CdSnP2 and CdSnAs2 crystals grown from melt

The best-developed polar faces (112) and (¯1¯1¯2) of CdSnP₂ and CdSnAs₂ crystals were identified by etch pits and by x-ray analysis. It is shown that the (112) faces are completed by group V atoms (phosphorus, arsenic), while the (¯1¯1¯2) faces are completed by cadmium and tin atoms. It is established that these faces of doped and undoped crystals differ in surface resistivity, conductivity type, and photoluminescence yield, and the material of their growth sectors has different Hall parameters.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 49–52, November, 1981.     

Influence of copper impurity and structure defects on the properties of compound CdSnAs2

A study was made of the mechanisms of formation and interaction of impurities and intrinsic defects in CdSnAs₂ crystals during diffusion doping of this compound with copper and during subsequent low-temperature (300°C) annealing. This was done by diffusing copper into samples with different initial defect structure under conditions of controlled arsenic vapor pressure and applying the method of quasichemical reactions to analyze the experimental data. It was found that the special features of the physical properties of n-type CdSnAs₂:Cu crystals — the low density and high mobility of electrons-were due to the high reactivity of copper resulting in binding of the original crystal defects to form neutral complexes. It was found that the anomalous annealing of CdSnAs₂: Cu samples, resulting in n-p conversion of the type of conduction, was associated with precipitation of a solid solution of an accidental donor impurity (most probably oxygen). The diffusion doping with copper was found to be one of the most effective methods for controlling the properties of CdSnAs₂, particularly in the preparation of high-resistivity crystals.Translated from Izvestiya Uchebnykh Zavedenii, Fizika, No. 5, pp, 102–108, May, 1980.     

Valence band and chemical interactions of Zn/CdSnAs2 interfaces

X-ray photoelectron spectroscopy (XPS) together with argon ion sputtering was used to investigate the interface of the Zn/CdSnAs₂ system at various temperatures. The formation of an intermediate compound between Zn and As is proposed. The surface enrichment of Cd and Sn at 200 and 400°C is explained in terms of bond breaking and lattice strain theories.NCL Communication No. 4352     

Investigation of the kinetic characteristics of heavily doped compensated CdSnAs2(Cu)

The concentrational dependences of the Hall coefficient and of the resistivity were used to investigate the interaction of diffusively introduced copper impurity with an ensemble of intrinsic defects inn-CdSnAs ₂. The initial electron density and the concentrations of theV _As andCu _As defects were found to be of the same order. A study was made of the dependence of the electrophysical properties ofCdSnAs ₂ (Cu) on the population of the impurity band and it was shown that the features of the kinetic characteristics ofCdSnAs ₂ (Cu) are determined by the absence of an energy gap between the bands with a conductivity of opposite sign and by the fact that one of the bands is an impurity band. State Pedagogical University, Nizhegorod. Kh. I. Amirkhanov Physics Institute, Dagestan Scientific Center, Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 62–66, May, 1997.     

Properties of lithium ion-conducting ceramics based on rare-earth titanates

The properties of complex oxides with perovskite structure of the Ln_2/3−XM_3XTiO₃ type (where Ln = rare-earth element and M = Li, Na, K) have been investigated. It has been shown that lithium - containing perovskites possess cationic conductivity, with values depending on the size of conducting channels and the concentration of vacant sites in the rare-earth ion sublattice. Paper presented at the 5th Euroconference on Solid State Ionics, Benalmádena, Spain, Sept. 13–20, 1998.     

Properties of transistor based C60 thin film on polystyrene

This paper reports that the n-type organic thin-fihn transistors have been fabricated by using C60 as the active layer and polystyrene as the dielectric. The properties of insulator and the growth characteristic of C60 film were carefully investigated. By choosing different source/drain electrodes, a device with good performance can be obtained. The highest electron field effect mobility about 1.15 cm2/（V. s） could reach when Barium was introduced as electrodes. Moreover, the C60 transistor shows a negligible ＇hysteresis effect＇ contributed to the hydroxyl-free of insulator. The result suggests that polymer dielectrics are promising in applications among n-type organic transistors.     

基于电润湿微棱镜技术的可调光衰减器特性分析

利用电控改变固液界面湿润角的电润湿微棱镜(EMPs)技术以及双自聚焦透镜组合设计了一类新颖的可调光衰减器,并对该衰减器的衰减性能进行了原理分析和实验测量.理论分析和实验结果表明其具有良好的光衰减控制效应,在不大的电压变化范围(例如135—139V)内即可实现2—60dB的光衰减范围.该器件构思新颖,具有结构简单、容易制作的优点,经过优化后将会在光通信领域得到广泛的应用.缺点是工作电压偏高,需要进一步筛选出介电系数高的物质来作为介电绝缘层材料,以便降低工作电压,达到实际可以使用的目的. 关键词： 微流控光学 电湿效应 可调光衰减器 电润湿微棱镜     

MgB_2超导体输运特性的研究

文中对 Mg B2 超导体的制备过程 ,对其同位素效应、电阻率、I- V曲线、热电势、电导涨落效应、能隙、霍尔效应、热重 -差热分析实验等输运特性进行了较全面的综述 ,并讨论了在 Mg B2 超导体基础上的元素替代效应。     

MgB2超导线拉伸性能研究

MgB2 是一种新型超导材料, 它具有较高的临界温度和较低的原料价格. 随着磁约束核聚变实验技术的发展, 未来的托卡马克磁体系统的低场部分磁体有希望使用 MgB2 CICC 导体绕制. CICC 导体的有限元分析需要以超导线的应力-应变函数为基础. 本文中, 来自西部超导公司( WST) 及 Hyper Tech 公司的两种 MgB2 超导线被测试了抗拉强度与弹性模量. 未反应的超导线在室温下的拉伸曲线被用多项式及指数函数拟合. 实验发现西部超导公司的 MgB2 线材在各种条件下的拉升强度都高于 Hyper Tech 线材. 室温下未反应的 MgB2 超导线的应力-应变关系可以用指数函数恰当地拟合, 并且表达式比多项式函数的拟合结果更简单. 超导线的应力-应变函数可以为CICC 导体数学模型的建立提供参考.     

Properties of three-dimensional composites based on opal matrices and magnetic nanoparticles

Three-dimensional nanocomposites consisting of an opal matrix and a metal have been prepared by the interaction of salts and oxides of different elements (Ni, Co, Fe, etc.) embedded in an opal matrix with isopropanol in the range of supercritical state parameters of the alcohol. According to X-ray powder diffraction analysis and transmission electron microscopy data, the composites consist of an X-ray amorphous opal matrix with pores filled by nanoparticles of Co (or CoO _x ), metallic Ni, or Fe₃O₄ with a magnetite structure of various morphology. The sizes of the nanoparticles do not exceed the diameter of the pores in the opal matrix. A complex investigation of the nanocomposites has been performed using the electron magnetic resonance and vibrating magnetometry methods. All the studied samples at room temperature exhibit a ferromagnetic behavior. The coercive force of the samples lies in the range from 150 Oe for iron-containing nanocomposites to 565 Oe for cobalt-containing nanocomposites.