Excitons in coupled quantum dots

Properties of excitons in vertically coupled GaAs/AlGaAs quantum dots were investigated using the variational method within the envelope function and effective mass approximations. It was found that when the thickness of the spacer layer becomes less than about one exciton Bohr radius, both the exciton binding energy and the fundamental optical transition energy are reduced compared to those in isolated quantum dots. This is a result of increased space extension of exciton due to the penetration of carrier wave functions into the spacer layer and corresponding reduction in confinement energy which dominates over the Coulomb interaction between the electron and the hole.     

C++QED: an object-oriented framework for wave-function simulations of cavity QED systems

We present a framework for efficiently performing Monte Carlo wave-function simulations in cavity QED with moving particles. It relies heavily on the object-oriented programming paradigm as realised in C++, and is extensible and applicable for simulating open interacting qua ntum dynamics in general. The user is provided with a number of “elements”, e.g. pumped moving particles, pumped lossy cavity modes, and various interactions to compose complex interacting systems, which contain several particles moving in electromagnetic fields of various configurations, and perform wave-function simulations on such systems. A number of tools are provided to facilitate the implementation of new elements.     

Syntheses and Structures of Heterometallic Fe–Ta Chalcogenido Clusters

Two Fe–Ta containing sulfido complexes were prepared by the reaction of the metal halide salts with bis-trimethylsilylsulfide in the presence of PMe₃. The complexes demonstrate that coordination chemistry with iron sulfides can give access to a range of heterometallic complexes. In [Cl(Me₃P)Ta( ₂-S)₂( ₃-S)Fe(PMe₃)₂]₂ the two [Cl(Me₃P)Ta] units are arranged around one central Fe₂( ₂-S)₂ unit. In [(Me₃P)₄(MeCN)₂Fe^II]²⁺[(Me₃P)₂Ta^IVFe^II ₃( ₃-S)₄Br₄]^2– a [TaFe₃S₄]²⁺ cuboidal arrangement was observed. The complex salt forms a polymeric structure in the solid-state with weak H-bonds between the ions. The [(Me₃P)₂Ta^IVFe^II ₃( ₃-S)₄Br₄]^2– ion was characterised by magnetic measurements showing strong antiferromagnetic interactions between the metal centres.     

Specific heat on Sr<Subscript>2</Subscript>Nb<Subscript>2</Subscript>O<Subscript>7</Subscript> and Sr<Subscript>2</Subscript>Ta<Subscript>2</Subscript>O<Subscript>7</Subscript>

Summary Specific heats on the single crystals of Sr₂Nb₂O₇, Sr₂Ta₂O₇ and (Sr_1-xBa_x)₂Nb₂O₇ were measured in a wide temperature range of 2-600 K. Heat anomalies of a λ-type were observed at the incommensurate phase transition of T_INC (=495 K) on Sr₂Nb₂O₇ and at the super-lattice phase transition of T_SL (=443 K) on Sr₂Ta₂O₇; the transition enthalpies and the transition entropies were estimated. Furthermore, a small heat anomaly was observed at the low temperature ferroelectric phase transition of T_LOW (=95 K) on Sr₂Nb₂O₇. The transition temperature T_LOW decreases with increasing Ba content x and it vanishes for samples of x>2%.     

复合光催化材料H3PW122O40/Ta2O5光催化降解染料的研究

采用溶胶-凝胶法制备了半导体型金属氧化物Ta2O5,并通过浸渍法与杂多酸H,PW12O40复合,获得了纳米复合光催化材料H3PW12O40/Ta2O5.通过1CP-AES、FT-lR、N2吸附、Tc等手段对其组成、结构及其表面物理化学性质进行了表征,并在可见光下考察了该复合材料对可溶性染料罗丹明B和亚甲基蓝的光催化活性.实验结果表明,该复合材料存可见光下有较好的光催化活性,其中,H3PW12O40/Ta2O5在180min内对亚甲基蓝的光催化降解转化率达到78%.     

Phase composition and phase transformation in Bi(Sb,Nb,Ta)O4 system

In this work Bi(Sb_xNb_yTa_z)O₄ (x + y + z = 1) samples are prepared using mixed-oxide method. A pseudo-ternary phase diagram of Bi(Sb,Nb,Ta)O₄ system is given below the melting point. It is composed of a monoclinic phase region, an orthorhombic phase region and a monoclinic–orthorhombic co-existing phase region. In the orthorhombic phase region, the transformation from orthorhombic to triclinic phase is found to be sensitive to the composition and sintering temperature. Both the transformation from monoclinic to orthorhombic structure and the transformation from orthorhombic to triclinic structure have been studied by the cell parameters.     

稀土－铌(钽)复合溴氧化物的结构与光谱特性

用高温固相法合成了系列化合物RE_0.06La_0.94M₂O₆Br(M=Nb,Ta;RE=Eu,Tb,Pr,Sm),并测定了其激发和发射光谱,室温下Eu³⁺、Tb³⁺、Pr³⁺、Sm³⁺在稀土-铌(钽)复合溴氧化物中呈现特征激发谱线,但Nb和Ta的光谱特性稍有不同。     

Ti基IrO2＋Ta2O5阳极在H2SO4溶液中的电解时效行为

研究了450 ℃制备所得Ti/70％IrO2 30％Ta2O5（摩尔分数）高寿命阳极在H2SO4溶液电解过程中电极的物理、化学及电化学性能的时效行为.结果发现，整个电解过程可分为“活化”、“稳定”及“失效”三个阶段.在“活化”及“稳定”区内主要发生电极表面活性氧化物的溶解，涂层中IrO2金红石相的（110）、（101）晶面择优取向随电解时间延长而减弱，而（002）晶面择优增强.但是在“失效区”内，各晶面的择优程度却不随电解时间的变化而变化，这表明在“失效区”内氧化物的损失机制发生了变化.电化学阻抗谱测试表明，电极的析氧电化学反应电阻随电解时间的延长发生缓慢而连续的上升，而整个电极的物理阻抗在“失效区”内却发生突升现象.X射线衍射分析（XRD）表明，随电解时间的延长TiO2金红石相的衍射强度增大，达“失效区”时衍射强度发生突升.根据实验现象特别是“失效区”内阳极的时效行为提出高寿命Ti基氧化物涂层阳极的失效机制.     

Structure Analysis of Needle-like Copper Tantalum Trisulfide Crystals by XPS and Raman Spectroscopy

High-quality needle-like CuTaS3 single crystals have been synthesized through a chemical vapor transport(CVT)process.Crystallographic data show the special double chains of edge-sharing TaS6 octahedra....