关键词： PAMAM树形分子   CdS-ZnS核-壳量子点   自组装   光致发光   超薄膜  

摘要： 制备了表面带负电荷的CdS-ZnS核-壳结构量子点/聚酰胺-胺(PAMAM)树形分子纳米复合材料,并以其为阴离子,以聚二甲基二丙烯基氯化铵(PDDA)为聚阳离子自组装制备了光致发光(PL)超薄膜.对膜的生长均匀性、表面平整性及发光性能进行表征,发现膜的UV-Vis吸收强度和PL强度随层数增加呈线性增大,表明每层膜均匀生长;AFM照片表明单个复合层膜非常平整,10层膜仍具有良好的平整度,并发出明亮的蓝绿色光。

关键词： 量子点   碳纳米管   电导  

摘要： 在紧束缚近似下,利用常量相互作用模型和Landauer-Bütticker公式,计算了扶手椅型和金属锯齿型碳纳米管量子点的电导.发现,根据碳纳米管量子点的长度的不同,扶手椅型碳纳米管量子点的电导可以具有两电子或四电子的壳层结构.而锯齿型碳纳米管量子点的电导却仅有四电子的壳层结构,与长度无关;这些理论结果与之前的实验结果符合的很好.

关键词： .randomness   long distances   quantum radiation   multilayer structures   quantum communication   nonlocalized   ENTANGLEMENT TRANSFORMATION   entangled-states   present systems   random degree  

摘要： The quantum radiation through the multilayer structures containing the left-handed materials is investigated based on the Green-function approach to the quantization of the phenomenological Maxwell theory. Emphasis is placed on the effect of randomness on the generation and transmission of entangled-states. It is shown that some unusual properties appear for the present systems in comparison with those of the conventional dielectric structures. The quantum relative entropy is always enhanced with the increase of random degree due to the existence of nonlocalized mode in the present systems, while the maximal entanglement can be observed only at some certain randomness for the conventional dielectric structures. In contrast to exponential decrease in the conventional systems, the entanglement degrades slowly with the increase of disorder and thickness of the sample near the nonlocalized mode after transmission through the present systems. This will benefit the quantum communication for long distances. 2008 Optical Society of America

关键词： ELECTRIC fields   ELECTRONS   FIELD-effect transistors   HETEROSTRUCTURES   METAL oxide semiconductor field-effect transistors   MODULATION-doped field-effect transistors   MATHEMATICAL models  

摘要： We have investigated analytically the influence of band non-parabolicity on the quantized gate capacitance in n-channel inversion layers of AlxGa1-xAs vertical bar GaAs, In1-xAsxSb vertical bar InSb, and In1-xAlxAs vertical bar In1-xGaxAsyP1-x delta-doped modulation field effect devices, whose channel electrons obey the three, two, and the parabolic energy band models of Kane. The quantized gate capacitance has been investigated by including the effects of electric subbands under quantum mechanical treatment on GaAs, InSb, and In1-xGaxAsyP1-y lattices matched to InP as channel materials. The oscillatory dependence of the quantized gate capacitance as a function of surface electric field and gate bias signatures directly the two-dimensional quantum confinement of the carriers. The influence of the band non-parabolicity of the confined carriers significantly influences the value of the gate capacitance. The result of the gate capacitances for the parabolic energy band model forms a special case of our generalized theoretical formalism. (c) 2008 American Institute of Physics. [DOI: 10.1063/1.2986154]

关键词： 量子线   量子点   自旋输运  

摘要： 提出了理想量子线通过量子点与铁磁导线侧向耦合系统,可实现电子自旋极化输运.并通过格林函数法计算表明:量子线上的电导产生自旋极化;电导极化率在反共振区有2个峰值,且与非共振区的极化方向相反;调整量子点和铁磁导线的耦合强度参数可使电导极化率达到极值.

关键词： magnetic quantization   non-linear   III-V   experimental determination  

摘要： In this paper, we have investigated the Einstein relation for the diffusivity-to-mobility ratio (DMR) under magnetic quantization in non-linear optical materials on the basis of a newly formulated electron dispersion law by considering the crystal field constant, the anisotropies of the momentum-matrix element and the spin-orbit splitting constant, respectively, within the frame work of k.p formalism. The corresponding result for the three-band model of Kane (the conduction electrons of III-V, ternary and quaternary compounds obey this model) forms a special case of our generalized analysis. The DMR under magnetic quantization has also been investigated for II-VI (on the basis of Hopfield model), bismuth (using the models of McClure and Choi, Cohen, Lax and parabolic ellipsoidal, respectively), and stressed materials (on the basis of model of Seiler et al.) by formulating the respective electron statistics under magnetic quantization incorporating the respective energy band constants. It has been found, taking n-CdGeAs2, n-Hg1-xCdxTe, p-CdS, and stressed n-InSb as examples of the aforementioned compounds, that the DMR exhibits oscillatory dependence with the inverse quantizing magnetic field due to Subhnikov de Haas (SdH) effect with different numerical values. The DMR also increases with increasing carrier degeneracy and the nature of oscillations are totally dependent on their respective band structures in various cases. The classical expression of the DMR has been obtained as a special case from the results of all the materials as considered here under certain limiting conditions, and this compatibility is the indirect test of our generalized formalism. In addition, we have suggested an experimental method of determining the DMR for degenerate materials under magnetic quantization having arbitrary dispersion laws. The three applications of our results in the presence of magneto-transport have further been suggested. (C) 2008 Elsevier B.V. All rights reserved.

关键词： 离子注入   晶格应变   X射线衍射光谱  

摘要： 对于GaAs衬底（100）面上用金属有机物气相淀积（MOCVD）技术外延生长的GaInP／GaInAsP单量子阱，在室温下进行0.28MeV的Zn^＋离子注入，选用的注量从1×10^14～5×10^14cm^-2。通过双晶X射线衍射光谱测量，定量地分析了由于离子注入所引起的晶格内应变。实验结果表明在所选用的注量下，由于离子注入引起的应变小于体材料GaAs的最大非弛豫应变值0.038，说明在这样的注入条件下，注入区的结晶态仍然保持地比较好。在较高注量下应变达到饱和，应变的饱和说明缺陷的产生和复合达到了平衡，从而形成了均衡的应变场分布。

关键词： 耦合量子点桥   非平衡格林函数   电子输运   透射概率  

摘要： 设计一个与4个电极相连的耦合量子点桥系统,该系统由两个量子点线构成,同时通过其间一个量子点耦合起来。利用非平衡格林函数的运动方程与Dyson方程,推导出通过这种系统的电流表达式。

关键词： 量子点   近藤效应   RKKY相互作用  

摘要： 本文阐述了杂质自旋与量子点净自旋间RKKY相互作用和近藤效应间的竞争对输运的影响,并进一步探讨给系统外加一磁场,在杂质和量子点的耦合为铁磁和反铁磁两种情况下,磁场对系统输运的影响以及磁场诱导的近藤和反铁磁间的相变。

关键词： 介观系统   量子输运   量子线   量子点  

摘要： 该文介绍介观系统量子输运的一些现象并进行理论分析,指出有待解决的问题及新的机遇.