Optical constants of Cu(In0.7Ga0.3)5Se8 and Cu(In0.4Ga0.6)5Se8 crystals

Variable angle spectroscopic ellipsometry has been applied to characterize the optical constants of bulk Cu(In_0.7Ga_0.3)₅Se₈ and Cu(In_0.4Ga_0.6)₅Se₈ crystals grown by the Bridgman method. The spectra were measured at room temperature over the energy range 0.8-4.4 eV. Adachi’s model was used to calculate the dielectric functions as well as the spectral dependence of complex refractive index, absorption coefficient, and normal-incidence reflectivity. The calculated data are in good agreement with the experimental ones over the entire range of photon energies. The parameters such as strength, threshold energy, and broadening, corresponding to the E₀, E_1A, and E_1B interband transitions, have been determined using the simulated annealing algorithm.     

The crystal structure of Fe2In2Se5, a FeIn2Se4-related polytype

Fe₂In₂Se₅, a polytype of FeIn₂Se₄ (a material belonging to the II □ III₂ VI₄ family of semiconducting compounds) has been synthesized by conventional solid-state reaction of their constituent elements. The product of the reaction was sequentially used as starting material in the crystal growth process carried out by chemical transport using I₂ as transporting agent. The crystal structure of a new polytype of this compound was determined using single crystal techniques with data collected with a CCD-based diffractometer. The successful indexing of the data and refinement of the structure led to an hexagonal unit cell with a=4.0371(4) and c=32.746(4) Å. Although the absorption effect in the data was quite noticeable, because of the layered morphology exhibited by the material, a good agreement was obtained for a structural model similar to the structure reported for a related polytype belonging to the ZnIn₂S₄ system.     

Metastable complex defects in α-(Al0.02In0.98)2Se3

The electrical properties of α-(Al_0.02In_0.98)₂Se₃ were investigated. In contrast to In₂Se₃, which is characterized by a high and constant concentration of donorlike defect centers, the concentration of active donors in α-(Al_0.02In_0.98)₂Se₃ can be changed in a reversible manner over four orders of magnitude by thermal treatment. To explain this strange behavior, we have proposed a simple model, which presumes formation of complex defect centers consisting of Al atoms at cation sites and native donors.     

Susceptibility measurements on some R5In3 compounds

The magnetic susceptibility of some rare earth-indium compounds has been measured in the temperature range 4.2–300 K under a constant field of 1 kOe. The compounds with R = Gd, Tb and Dy are antiferromagnetic, having Néel temperatures between 4.2 and 78 K ; those with R = Ho, Er and Tm seem to be ferromagnetic with ordering temperatures probably below 4.2 K. Y₅In₃ presents a temperature independent susceptibility.     

Magnetic and transport properties of Mn-doped Bi2Se3 and Sb2Se3

We report on the single crystal growth and thermoelectric and magnetic properties of Mn-doped Bi₂Se₃ and Sb₂Se₃ single crystals prepared by the temperature gradient solidification method. The composition and crystal structure were determined using electron probe microanalysis and θ–2θ powder X-ray diffraction studies, respectively. The lattice constants of several percent Mn-doped Bi₂Se₃ and Sb₂Se₃ were slightly smaller than those of the undoped sample due to the smaller Mn atomic radius (1.40 Å) than those of Bi (1.60 Å) and Sb (1.45 Å). Mn-doped Bi₂Se₃ and Sb₂Se₃ showed spin-glass and paramagnetic properties, respectively.     

Cr-related centers in Gd3Ga5O12 polycrystals

The luminescence excitation spectra, emission spectra under photo- and X-ray excitation, luminescence decay kinetics and thermostimulated luminescence (TSL) of Gd₃Ga₅O₁₂ garnet (GGG) polycrystalline samples have been investigated. It was established that the spectrum of Cr³⁺ ion emission were present in all TSL peaks. The activation energies of traps that are responsible for appearance of TSL in the region 295-600 K were estimated. It is shown that delocalization of electrons from the Cr³⁺e traps leads to the appearance of thermoluminescence (TL) glow peak at 390 K. The nature of other TSL peaks is discussed. The influence of visible light on the TSL intensity of the preliminary X-ray-irradiated samples is shown.     

非等电子Sb替换Cu和Te后黄铜矿结构半导体Cu_3Ga_5Te_9的热电性能

热电材料是一类能够实现热与电相互转换的功能材料,在制冷和发电领域极具应用潜力.本文采用金属Sb元素非等电子替换Cu3Ga5Te9化学式中的Cu和Te,观察到材料Seebeck系数和电导率提升的现象.这些电学性能的改善与载流子浓度和有效质量的增大及迁移率基本维持不变有关.载流子浓度的提高是由于Sb原子占位在Te晶格位置后费米能级进入到价带所产生的空穴掺杂效应所致,同时也与Cu含量减少后铜空位(V-1Cu)浓度增大相关联.另外,非等电子替换后,阴离子(Te2-)移位导致了晶格结构缺陷参数u和η的改变,其改变量fiu和fiη与材料晶格热导率(κL)的变化密切相关.在766 K时,适量的Sb替换量使材料的最大热电优值(ZT)达到0.6,比Cu3Ga5Te9提高了近25%.因此,通过选择替换元素、被替换元素及替换量有效地调控了材料的电学及热学性能,在黄铜矿结构半导体中实现了非等电子元素替换改善热电性能的思想.     

Voltage-decreased electro-optical Q-switch of La3Ga5SiO14 crystal

We present a novel method to achieve voltage-decreased electro-optical Q-switch with three different blocks of optically active crystal. The dynamic/static energy rate can be up to 82%. We also find a theory function to explain the achievement of Q-switch and find the requirement of the achievement of voltage-decreased Q-switch with optically active crystal. The theory coincides with the experiment result well.     

Spectroscopic properties of Er/Ce-codoped La3Ga5SiO14

The Er-single-doped and Er/Ce-codoped La₃Ga₅SiO₁₄ polycrystalline powders are synthesized by the solid-phase synthesis method. The room-temperature luminescence spectra of the samples are investigated. The Near-infrared-region spectroscopic properties of Er³⁺ ions in the La₃Ga₅SiO₁₄ systems are analysed with Judd-Ofelt theory and rate equations. The effective deactivating effect of Ce³⁺ ions on Er³⁺ ions is confirmed.     

Novel RCo5Ga7 intermetallic compound

The novel RCo₅Ga₇ (R=Y, Tb, Dy, Ho and Er) intermetallic compounds have been synthesized, and their crystallographic and magnetic properties have been studied using X-ray diffraction and magnetic measurement. RCo₅Ga₇ crystallizes in an orthorhombic structure with ScFe₆Ga₆ type. The space group is Immm, and Z=2. According to the structural refinement result, the 2a, 4e, 4f, 4g, 4h, and 8k crystal positions are occupied by 2R, 4Ga^I, 4(Ga^II, Co^I), 4Ga^III, 4(Ga^IV,Co^II), and 8(Co^III,Ga^V), respectively. The RCo₅Ga₇ intermetallic compound can be stabilized in the range of the radius ratio of R_Re/R_(Co,Ga)<1.36. The RCo₅Ga₇ compound exhibits a paramagnetic behavior. The magnetization at 5 K ranges from 28.93 to 40.62 emu/g.     

Phase formation and characterization of Sr3Y2Ge3O12, Sr3In2Ge3O12, and Ca3Ga2Ge3O12 doped by trivalent europium

This work reports on the phase formation during a solid-state reaction of Eu³⁺-doped garnets with the general formula A₃B₂Ge₃O₁₂ (A=Ca, Sr and B=Ga, In, Y) and their luminescent properties. It is shown by XRD and DTA/TG experiments that the garnet-phase formation is completed at 1100-1200 °C. Moreover, it turned out that the position of the oxygen to europium charge-transfer band and the intensity of the forbidden 4f-4f transitions of Eu³⁺ is dependent on the covalent interaction between the Eu³⁺ activator and the surrounding oxygen anions. The investigated red-emitting luminescent materials show high lumen equivalents and deep red emission at the same time, which makes them attractive for the application in LEDs (light emitting diodes), in particular for near UV-emitting LEDs.     

Sputtering of amorphous ice induced by C60 and Au3 clusters

Molecular dynamics simulations were performed to study the behavior of cluster SIMS. Two predominant cluster ion beam sources, C₆₀ and Au₃, were chosen for comparison. An amorphous water ice substrate was bombarded with incident energy of 5 keV. The C₆₀ cluster was observed to shatter upon impact creating a crater of damage approximately 8 nm deep. Although Au₃ was also found to both break apart and form a damage crater, it continued along its initial trajectory causing damage roughly 10 nm deep into the sample and becoming completely imbedded. It is suggested that this difference in behavior is due to the large mass of Au relative to the substrate water molecule.     

Electro- and thermoreflectance of Bi2Te3 and Bi2Se3

Electroreflectance measurements in Bi₂Te₃ and Bi₂Se₃ with the electric field vector of the incident light both inclined and perpendicular to the C-axis have been made at room temperature. The structures found by other workers in the reflection measurements are observed in the present experiment, together with new structures at 0.91 eV, 1.18 eV, 1.78 eV, and 2.61 eV in Bi₂Se₃ which are not related to formerly observed transitions. From these measurements, the selection rules for direct optical transitions in Bi₂Te₃ and Bi₂Se₃ are studied. Thermoreflectance measurements are also made at both room and liquid-nitrogen temperatures. The positions of the peaks obtained in the present work are compared with the electroreflectance and reflection data.     

High-performance langasite (La3Ga5SiO14) electro-optic Q-switch

By cone-light interference method, the best langasite ( La₃Ga₅SiO₁₄, LGS) crystal is chosen to make an electro-optic Q-switch. When the input energy is 28 J, the Q-switched output is 360 mJ. The stability is 0.45%; the dynamic–static ratio is 80.05%; and the total electric-optical conversion efficiency is 1.3%.     

Low-temperature electrical properties of V2Ga5

Electrical and magnetic measurements are reported for V₂Ga₅ crystals. A transition to the superconducting state was observed at 4.2 K. The temperature dependence of the critical fields and the Ginzburg-Landau-parameter ? were also determined. Information is also given about the temperature dependence of the ideal electrical resistivity between 10 and 300 K.     

钆镓石榴石单晶的喇曼光谱

测量了助熔剂法和提拉法生长的钆镓石榴石单晶的喇曼光谱。识别了该晶体的喇曼活性声子。和文献[6]相比,本文得到了更完全的结果。我们也比较了两种方法生长的晶体的喇曼谱,声子模式彼此一致。发现一些不同的谱线,这被识别为不同稀土掺杂离子的荧光谱线。 关键词：     

V2Ga5的晶体结构

本文利用单晶与粉末衍射方法测定了V₂Ga₅的晶体结构。V₂Ga₅属四方晶系,其单相区约为VGa₂—V₂Ga₅。在18℃的点阵常数是a=8.9540?,c=2.6892?,每个晶胞含有二个化合式量,空间羣为D_4h⁵—P4/mbm。V原子与Ga原子分别占据在4(h)与8(i),2(d)的等效位置上。参数为:x相似文献   

Low temperature photoconductivity of ZnIn2Se4 and CdIn2Se4

The photoconductivity of ZnIn₂Se₄ and CdIn₂Se₄ single crystals has been studied at 4.2 K. The spectra are compared to reflectivity spectra and relevant structures are interpreted in terms of interband transitions. The absence of excitonic transitions is discussed in connection with the crystalline perfection.     

Electronic properties of Bi2Se3 crystals

Bismuth selenide crystals were grown from melts with liquid concentrations within 0·2 per cent of stoichiometry. The resulting crystals were examined structurally showing that single crystal samples could be cut for electronic property measurements. Samples were n-type and degenerate (n ～ 2 × 10²⁵ m^?3). Hall, magnetoresistance and Shubnikov-de Haas measurements confirm that the carriers lie in a single minimum located at the centre of the Brillouin Zone. The results are discussed in terms of a non-ellipsoidal band model, and the degeneracy discussed in terms of a defect model.     

Jahn-Teller band transition in La3S4 and La3Se4

La₃S₄ and La₃Se₄ undergo a cubic to tetragonal phase transformation at a temperature of 103 and 70 K respectively, the c/a ratio is 0.984 for La₃S₄ and 0.987 for La₃Se₄. In these compounds the conduction electron Fermi energy happens to be close to a band structure anomaly which drives the phase transition. We find some indication, that the anomaly might be of ?-type.