Quantum-confinement-effect-driven type-I-type-II transition in inhomogeneous quantum dot structures

We investigate the electronic structures of the inhomogeneous quantum dots within the framework of the effective mass theory. The results show that the energies of electron and hole states depend sensitively on the relative magnitude 77 of the core radius to the capped quantum dot radius. The spatial distribution of the electrons and holes vary significantly when the ratio eta changes. A quantum-confinement-driven type-II-type-I transition is found in GaAs/AlxGa1-xAs-capped quantum dot structures. The phase diagram is obtained for different capped quantum dot radii. The ground-state exciton binding energy shows a highly nonlinear dependence on the innner structures of inhomogeneous quantum dots, which originates from the redistribution of the electron and hole wave functions.

Observation of field-driven blue shift in delta-doped Si n-i-p-i multiple quantum wells

We report the observation of the field-driven blue shift at near absorption edge in the photo-current response spectra of delta-doped Si n-i-p-i multiple quantum wells due to the widening of the effective energy gap. This phenomenon differs from the observed results in GaAs/AlGaAs and GeSi/Si superlattices, because the physical mechanisms of forming energy band in these superlattice samples are different. Our experimental results are interpreted satisfactorily by the theoretical calculation. (C) 1999 Elsevier Science Ltd. All rights reserved.

On the performance analysis and design of a novel shared-layer integrated devices using RCE-p-i-n-PD/SHBT - art. no. 67820J

We have explored the shared-layer integration fabrication of an resonant-cavity-enhanced p-i-n photodector (RCE- p-i-n-PD) and a single heterojunction bipolar transistor (SHBT) with the same epitaxy grown layer structure. MOCVD growth of the different layer structure for the GaAs based RCE- p-i-n-PD/SHBT require compromises to obtain the best performance of the integrated devices. The SHBT is proposed with super-lattice in the collector, and the structure of the base and the collector of the SHBT is used for the RCE. Up to now, the DC characteristics of the integrated device have been obtained.

network and device-level impacts: performance and reliability of active i/o storage systems

中国计算机学会

I.茚基和环戊二烯基钕二氯化物-烷基铝二元体系催化丁二烯聚合反应动力学II.萘基钕及二环戊二烯基钕化合物的合成

本文研究所了四种钕化合物（茚基钕有机金属化合物C_9H_7NdCl_2·HCl·C_4H_8O，环戊二烯基钕有机金属化合物-C_5H_5NdCl_2·C_4H_8O，无水氯化钕络合物-NdCl_3·2C_4H_8O及NdCl_3·C_6H_5OH·C_4H_8O）与三异丁基铝（i-Ba_3Al）或一氢二异丁基铝（i-Bu_2AlH）所组成的二元催化体系中丁二烯聚合动力学。这些体系的动力学特点尚未被人们研究，通过实验揭示出一些新的规律，丰富了我们对稀土体系催化丁二烯聚合动力学的认识。研究中着重考察了聚合物活性链的变化条件，从而能较深刻地认识各体系的动力学特点，结果表明：C_9H_7NdCl_2·HCl·C_4H_8O，C_5H_5NdCl_2·C_4H_8O，NdCl_3·2C_4H_8O，NdCl_3·C_6H_5OH·C_4H_8O与i-Bu_2AlH所组成的二元催化体系中，当[Mo]=1.11克分子/升、[Nd]=1.12*10~(-4)克分子/升、[i-Bu_2AlH]\3.36*10~(-3)克分子/升、50 ℃聚合时为缓慢引发非稳态聚合反应。而当增加铝用量至[i-Bu_2AlH] = 6.72*10~(-3)克分子/升，C_9H_7NdCl_2·HCl·C_4H_8O体系转变为迅速引发稳态聚合反应，其余体系反应动力学行为无变化。各稀土钕催化体系动力学的差异主要是由配位体供电性不同产生的。当配位体供电性强时有利于降低稀土离子的正电荷，从而有利于烷基化反应和活性中心的形成和稳定，因此决定了各催化体系的不同动力学行为。C_9H_7NdCl_2·HCl·C_4H_8O体系当聚合温度、烷基铝浓度变化时以及Nd(naph)_3体系当温度变化时聚合物活性链状况会发生变化，从而改变了动力学行为。缓慢引发和迅速引发，稳态和非稳态间会发生转化而不是一成不变的。凝胶渗透色谱法应用于反应机理的研究不仅在理论上是可能的，在实践上是成功的。缓慢引发非稳态聚合（C_5H_5NdCl_2·C_4H_8O，NdCl_3·C_6H_5OH·C_4H_8O,NdCl_3·ZC_4H_8O），迅速引发非稳态聚合（Nd(naph)_3），迅速引发稳态聚合（C_9H_7NdCl_2·HCl·C_4H_8O）不同的动力学类型都具有不同的分子量分布特点。C_9H_7NdCl_2·HCl·C_4H_8O体系中丁二烯聚合速率方程为：K_p=K_p[C~*][M]. 50 ℃,[Nd]=1.12*10~(-4),[i-Bu_2AlH]=6.72*10~(-3)克分子/升条件下，丁二烯为快引发稳态聚合反应。此体系中活性中以浓度为2.43*10~(-6)克分子/升，催化剂有效利用率2%，链增长速率常数为81.42升/克分子，秒，聚合反应表观活化能为8.5±0.5千卡/克分子。聚合物顺-1，4结构均为98%左右。活性链平均寿命为7.22分钟。活性链对烷基铝的转移为主要链转移方式而对单体无明显转移。链转移速率常数为2.99升/克分子秒。

High-Saturation-Power and High-Speed Ge-on-SOI p-i-n Photodetectors

Ge-on-silicon-on-insulator p-i-n photodetectors were fabricated using an ultralow-temperature Ge buffer by ultrahigh-vacuum chemical vapor deposition. For a detector of 70-mu m diameter, the 1-dB small-signal compression power was about 110.5 mW. The 3-dB bandwidth at 3-V reverse bias was 13.4 GHz.

ELECTRONIC-STRUCTURES OF THE ALKALI-CONTAINING BUCKMINSTERFULLERENES (A-DELTA-C60) (A=LI,NA,K,RB,CS) AND THE HALOGEN-CONTAINING BUCKMINSTERFULLERENES (H-DELTA-C60) (H=F,CL,BR,I)

The geometrical parameters and electronic structures of C60, (A partial derivative C60) (A = Li, Na, K, Rb, Cs) and (H partial derivative C60) (H = F, Cl, Br, I) have been calculated by the EHMO/ASED (atom superposition and electron delocalization) method. When putting a central atom into the C60 cage, the frontier and subfrontier orbitals of (A partial derivative C60) (A = Li, Na, K, Rb, Cs) and (H partial derivative C60) (H = F, Cl) relative to those of C60 undergo little change and thus, from the viewpoint of charge transfer, A (A = Li, Na, K, Rb, Cs) and H (H = F, Cl) are simply electron donors and acceptors for the C60 cage resPeCtively. Br is an electron acceptor but it does influence the frontier and subfrontier MOs for the C60 cage, and although there is no charge transfer between I and the C60 cage, the frontier and subfrontier MOs for the C60 cage are obviously influenced by I. The stabilities DELTAE(X) (DELTAE(X) = (E(X) + E(C60)) - E(x partial derivative C60)) follow the sequence I < Br < None < Cl < F < Li < Na < K < Rb < Cs while the cage radii r follow the inverse sequence. The stability order and the cage radii order have been explained by means of the (exp-6-1) potential.