ВЛИЯНИЕ СТАРЕНИЯ НА Э ЛЕКТРИЧЕСКИЕ СВОЙСТ ВА ПОЛУПРОВОДНИКОВОЙ С ИСТЕМЫ Bi2Te3-Bi2Se3

, Bi₂Te₃-Bi₂Se₃. , , , . .

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Influence of ageing on change in electrical properties of semiconducting systems of Bi₂Te₃-Bi₂Se₃

The paper describes the effect of ageing observed on a semiconducting system Bi₂Te₃ — Bi₂Se₃. It is shown that the change in electrical conductivity and thermoelectric force, which takes place during ageing, is caused by the change in concentration of the free electrons. The influence of this process on the efficiency of equipment employing the Peltier effect is analyzed.

     

Determination of a pseudo-binary SrSe–Ga2Se3 phase diagram and single crystal growth of SrGa2Se4 compounds

We have investigated chemical reaction processes and thermal characteristics of IIa–III₂–VI₄ compounds in order to grow their single bulk crystals. Up to now, single crystals of Ca and Sr thiogallates have been successfully grown by the melt growth method based on their pseudo-binary phase diagrams. Here, a similar diagram of the SrSe–Ga₂Se₃ system has been constructed for the first time, where a eutectic reaction is found in the range of excess Ga₂Se₃ concentration, and it is shown that the SrGa₂Se₄ compound has a congruent melting point (1110 °C) suitable for the melt growth. A single crystal is grown from the melt by the horizontal Bridgman method. A trial is also made to grow a high-quality single crystal of CaGa₂S₄ already known as being grown easily.     

Elastic moduli and theoretical estimations of physical properties of Ge3Se7–As2Te3

The Bulk (100-x)Ge₃Se₇ - (x)As₂Te₃ (0 ≤ x ≤ 30) glassy alloys were prepared using the melt quenching technique. The elastic moduli (Bulk (K), Micro-hardness (H), Young (Y)), and Poisson's ratio (P_r) of the prepared glasses have been determined using the measured values of the ultrasonic velocities and density (ρ). Values of ρ were measured, then the molar volume (V_m) was estimated theoretically. The DSC thermograms are used to determine the glass transition temperature (T_g). The thermal evaporation method was used to prepare the (100-x)Ge₃Se₇- (x)As₂Te₃ (0 ≤ x ≤ 30) thin films under a vacuum of about 10⁻⁴Pa. The absorbance (A) of the films in the spectral range from 0.45 to 0.85 μm has been measured, then the absorption coefficient (α) and energy gap (E_g) were determined. The Chemical Bond Approach (CBA) has been used successfully to estimate theoretically various physical and structural characteristics of the studied system. Theoretical values of E_g and T_g have been obtained using different methods. The results proved a remarkable agreement between the theoretical and experimental values for both the E_g and T_g. The E_g values decreased from 2.1 to 1.73 eV by increasing the As₂Te₃ content from 0 to 30 at. %. Therefore, these compounds can be used as an absorbing layer for electromagnetic radiation in photovoltaic devices and sensors.     

Pre-exponential factor for the crystallization of glassy Se80Te20 and Se75Te20M5 alloys: applicability of Meyer–Neldel rule

The Meyer–Neldel rule or MN rule (also known as compensation effect) is an empirical law known since 1937. This rule is observed in wide range of phenomena in physics, chemistry, biology and electronics. Many activated phenomena, including solid state diffusion in crystals and polymers, dielectric relaxation, conduction and thermally stimulated processes in polymers, and electronic conduction in amorphous semiconductors obey the MN rule. In the present article, we report the MN rule in the non-isothermal crystallization in glassy Se₈₀Te₂₀ and Se₇₅Te₂₀M₅ (M = Ag, Cd, In, Sb) alloys. We have observed MN rule between pre-exponential factor K _o and activation energy of crystallization E _c in the present case for thermally activated non-isothermal crystallization.     

Study of 2β-decay of 100Mo and 82Se using the NEMO3 detector

After analysis of 5797 h of data from the detector NEMO3, new limits on neutrinoless double beta decay of ¹⁰⁰Mo (T _1/2>3.1×10²³y, 90% CL) and ⁸²Se (_{T 1/2}>1.4×10²³y, 90% CL) have been obtained. The corresponding limits on the effective majorana neutrino mass are: 〈m _v〉<(0.8–1.2) eV and 〈m _v〉<(1.5–3.1) eV, respectively. Also the limits on double-beta decay with Majoron emission are: T _1/2>1.4×10²²y (90% CL) for ¹⁰⁰Mo and T _1/2>1.2×10²²y (90% CL) for ⁸²Se. Corresponding bounds on the Majoron-neutrino coupling constant are 〈 g _ee〉<(0.5–0.9)×10^?4 and <(0.7?1.6)×10^?4. Two-neutrino 2β-decay half-lives have been measured with a high accuracy, $T_{1/2}^{100_{Mo} } = [7.68 \pm 0.02(stat) \pm 0.54(syst)] \times 10^{18} y$ and $T_{1/2}^{82_{Se} } = [10.3 \pm 0.3(stat) \pm 0.7(syst)] \times 10^{19} y$ .     

GaS0.4Se0.6: Relevant properties and potential for 1064 nm pumped mid-IR OPOs and OPGs operating above 5 μm

We present measurements of the transparency, refractive index dispersion, nonlinear coefficient, damage threshold, and two-photon absorption of mixed GaS _x Se_{1 − x} crystals and show that GaS_0.4Se_0.6 is a promising nonlinear material for down conversion of pulsed 1064 nm radiation to the mid-IR above 5 μm without significant two-photon absorption.     

Über Kristallstruktur und elektrische Eigenschaften der Wismutselenide Bi2Se2 und Bi2Se3

The properties of bismuth triselenide (Bi₂Se₃) are already known to a certain extent through the work of several authors, while it was still an open question whether there exists an individual solid phase of BiSe. Further information on this subject could be obtained by the successful growth and investigation of single crystals of both Bi₂Se₃ and Bi₂Se₂. X-ray analysis by means of goniometry, Weißenberg, Laue, and Debye-Scherrer diagrams confirmed the known crystal structure of Bi₂Se₃ (ditrigonal scalenohedral;D _3d ⁵ ?R—m; with the hexagonal axes:a=4·15 Å andc=28·55 Å, and 3 molecules per unit cell). As to Bi₂Se₂ it can be shown that it belongs to the same class but to a different space group (D _3d ¹ ?P— 1m orD _3d ³ ?P—m 1; hexagonal axes:a=4·15 Å,c=22·84 Å, unit cell: 3 molecules, if the formula Bi₂Se₂ is adopted). Common to both is a subcell with the dimensions:a′=a=4·15 Å andc′=5·71 Å. The temperature dependence of electrical conductivity and Hall coefficient was measured on several specimens having different crystal orientations. The most striking difference is the high anisotropy of Bi₂Se₃ (σ _a σ _c =10) as compared with Bi₂Se₂ (σ _a /σ _c <2). All specimens turned out to ben-type. The room temperature carrier concentration observed was:n (Bi₂Se3)=8·10¹⁸ cm^?3 andn (Bi₂Se₂)=4·10²⁰ cm^?3, the carrier mobility:μ(Bi₂Se3)=2·10³ cm²/V·s andμ(Bi₂Se₃)=20 cm²/V·s.     

非晶态Se向纳米晶体Se的转变

采用水淬法制备出块状非晶态硒,通过非晶晶化法获得了六方晶型结构的、晶粒尺寸为6—45nm的块状纳米晶硒,X射线衍射及热分析研究表明非晶态硒向纳米晶硒的转变是由一步晶化完成的,激活能为54—60kJ/mol.并证实了非晶硒的短程序与六方晶型硒相同以及非晶硒的无规线团结构.根据不同方向的晶粒尺寸与晶化温度的关系,发现沿c轴的生长速率大于沿a轴的生长速率.采用无规线团形的分子链在晶界处折叠或延伸到相邻晶粒中的晶化机制解释了晶化过程中激活能低和生长速率沿c轴方向较大的实验结果. 关键词：     

Molecular-beam epitaxy of topological insulator Bi2Se3 （111） and （221） thin films

This paper presents an overview of the growth of Bi2Se3, a prototypical three-dimensional topological insulator, by molecular-beam epitaxy on various substrates. Comparison is made between the growth of Bi2 Se3 （111） on van der Waals （vdW） and non-vdW substrates, with attention paid to twin suppression and strain. Growth along the [221] direction of Bi2Se3 on InP （001） and GaAs （001） substrates is also discussed.     

Renormalizing N3LO Nucleon–Nucleon Interactions with Multiple Subtractions and Infinite Cutoff: The 3 F 4 −3 H 4 and the 3 G 5− 3 I 5 Coupled Channels

We apply five subtractions to the scattering equation to renormalize the nucleon–nucleon interaction in coupled channels. We take as an example the coupled channels with total angular momentum J = (4, 5) for the interactions N3LO-EM and N3LO-EGM. The waves with L = J ? 1 and the mixing angles are rather independent of the renormalization scale while the waves with L = J + 1 show a slower convergence as the renormalization scale increases, but become scale invariant at μ ~ 1 fm^?1.     

Magnetic properties and magnetocaloric effects of Mn5Ge3-xGax

We report on the magnetic properties and magnetocaloric effects of Mn5Ge3-xGax compounds with x=0.1,0.2,0.3,0.4,0.6 and 0.9. All samples crystallize in the hexagonal Mn5Si3-type structure with space group P63/mcm and order ferromagnetically.The Curie temperature of these compounds decreases with increasing x, from 306K (x=0.1) to 274K (x=0.9).The average Mn magnetic moments increases with increasing Ga content,reaching a maximum value at x=0.6.The magnetic entropy changes in these compounds are determined from the temperature and field dependence of the magnetization using the thermodynamic Maxwell relation.The Ga substitution has two kinds of influence on the magnetocaloric effect (MCE) of Mn5Ge3.One is that the magnitude of the magnetic entropy change decreases,the other is that the MCE peak becomes broadened.     

Shapes and β-decay in proton rich Ge,Se, Kr and Sr isotopes

We study ground states and β-decay properties of the proton rich isotope chains Ge, Se, Kr, and Sr. We use a deformed selfconsistent HF+RPA approach with density-dependent effective interactions of Skyrme type. We find that most of the isotopes present two HF minima corresponding to two different shapes. In addition to static quadrupole moments and other ground state band properties, we present results for Gamow Teller strength distributions, as well as for half-lives and summed strengths. The role of deformation is particularly emphasized.     

若干In2Se3 化合物的晶体结构与电子特性

等离激元是金属中自由电子的集体振荡,其在物理,生物、化学、能源、信息等领域具有重要的应用前景。近些年来对等离激元量子效应研究的深入开展使得等离激元研究迈入了新阶段。本文首先简要介绍了等离激元的两个基本特性：光压缩效应和局域电场增强效应;随后回顾了量子等离激元方面的最新的进展,包括量子纠缠效应,量子尺寸效应,量子遂穿效应,等离激元在台阶势垒处的反射与激发,等离激元对电子相干效应的增强;最后对量子等离激元研究进行了总结和展望。     

若干In2Se3化合物的晶体结构与电子特性

In_2Se_3是一种常见的A_2~ⅢB_3~Ⅵ型半导体,在不同温度下可表现出不同的物相,对应的晶格参数与物理性质也会有所不同.在过去几十年间,In_2Se_3的多相性引起了人们的关注,各物相的晶体结构被广泛地研究.近年来,研究发现α-In_2Se_3具有优异的光电、压电性能以及独特的铁电性能,可以预见它将在未来的半导体电子器件中发挥出重要的作用.本文综述了一系列In_2Se_3化合物的晶体结构与电子特性,我们首先简要介绍了这些In_2Se_3化合物的基本知识,接着详细讨论了它们的晶体结构与电子特性,最后对In_2Se_3化合物的研究前景进行了展望.     

新型层状Bi2Se3的第一性原理研究

近年来,在石墨烯研究热潮的推动下,众多种类丰富、性能各异的二维化合物材料相继被发现,其中一些二维材料具有多种同素异构体,进而呈现出更丰富的性质.层状Bi2Se3由于其独特的物理性质,受到人们广泛的关注,而它的同素异构体尚未有人研究.本文采用基于密度泛函理论的结构搜索方法,预测了一个稳定的b-Bi2Se3新相,它具有良好...     

Thermal stability and crystallization kinetics of Ge–Se–Cd glasses

The effect is reported of varying cadmium concentration on the glass transition, thermal stability and crystallization kinetics of Ge₂₀Se_{80? x} Cd _x (x = 2.5, 5, 7.5 and 10 at. %) glasses. Differential scanning calorimetry results under non-isothermal conditions for the studied glasses are reported and discussed. The values of the glass transition temperature (T_g ) and the peak temperature of crystallization (T_p ) were found to be dependent on heating rate and Cd content. From the heating rate dependence of T_g and T_p , the values of the activation energy for glass transition (E_g ) and the activation energy for crystallization (E_c ) were evaluated and their composition dependence discussed. The thermal stability of the glasses was evaluated using various thermal stability criteria such as ΔT, H_g and S. The stability calculations emphasize that the thermal stability decreases with increasing Cd content.     

Structural and electrical properties of LiCo3/5Cu2/5VO4 ceramics

The LiCo_3/5Cu_2/5VO₄ compound is prepared by a solution-based chemical method and characterized by the techniques of X-ray diffraction, scanning electron microscopy and complex impedance spectroscopy. The X-ray diffraction study shows an orthorhombic unit cell structure of the material with lattice parameters a=13.8263 (30) Å, b=8.7051 (30) Å and c=3.1127 (30) Å. The nature of scanning electron micrographs of a sintered pellet of the material reveals that grains of unequal sizes (～0.2–3 μm) present an average grain size with a polydisperse distribution on the surface of the sample. Complex plane diagrams indicate grain interior and grain boundary contributions to the electrical response in the material. The electrical conductivity study reveals that electrical conduction in the material is a thermally activated process. The frequency dependence of the a.c. conductivity obeys Jonscher’s universal law.