~(13)C-NMR STUDY ON THE CHAIN TERMINAL STRUCTURE OF POLY-1,3-PENTADIENE POLYMERIZED WITH RARE EARTH CATALYST

The sequence distribution and the terminal structures of poly-1,3-pentadiene chains obtained by rare earth catalyst and effect of polymerization temperature on microstructure of the polymer have been investigated by ~(13)C-NMR method. According to experimental results it was supposed that terminal active growing chain of the polymer would be four types of anti- and syn-η~3-allyl structures. When polymerization temperature was reduced, the content of cis-1,4-poly-1,3-pcntadiene increases. It can be explained by isomerization between anti- and syn-η~3-allyl. The process forming trans-1,2 unit instead of 3,4-unit were also described.     

Improved performance of near UV light-emitting diodes with a composition-graded p-AlGaN irregular sawtooth electron-blocking layer

We investigate the performances of the near-ultraviolet(about 350 nm-360 nm) light-emitting diodes(LEDs) each with specifically designed irregular sawtooth electron blocking layer(EBL) by using the APSYS simulation program.The internal quantum efficiencies(IQEs),light output powers,carrier concentrations in the quantum wells,energy-band diagrams,and electrostatic fields are analyzed carefully.The results indicate that the LEDs with composition-graded pAl_xGa_(1-x)N irregular sawtooth EBLs have better performances than their counterparts with stationary component p-AlGaN EBLs.The improvements can be attributed to the improved polarization field in EBL and active region as well as the alleviation of band bending in the EBL/p-AlGaN interface,which results in less electron leakage and better hole injection efficiency,thus reducing efficiency droop and enhancing the radiative recombination rate.     

Effects of multiple interruptions with trimethylindium-treatment in the InGaN/GaN quantum well on green light emitting diodes

In this study, the influence of multiple interruptions with trimethylindium(TMIn)-treatment in InGaN/GaN multiple quantum wells(MQWs) on green light-emitting diode(LED) is investigated. A comparison of conventional LEDs with the one fabricated with our method shows that the latter has better optical properties. Photoluminescence(PL) full-width at half maximum(FWHM) is reduced, light output power is much higher and the blue shift of electroluminescence(EL) dominant wavelength becomes smaller with current increasing. These improvements should be attributed to the reduced interface roughness of MQW and more uniformity of indium distribution in MQWs by the interruptions with TMIn-treatment.     

第一性原理研究Te-N共掺p型ZnO

采用基于密度泛函理论的第一性原理赝势法对Te-N共掺杂ZnO体系的晶格结构、 杂质态密度和电子结构进行了理论分析.研究表明, N掺杂引起晶格收缩,而Te的掺入引起晶格膨胀, 从而减小晶格应力促进N的掺杂,并且Te由于电负性小于O而带正电, Te在ZnO中作为等电子施主而存在.研究发现, N掺杂体系中在费米能级附件形成窄的深受主能级, 而Te-N共掺体系中, N杂质带变宽,空穴更加离域,同时,空穴有效质量变小,受主能级变浅, 更有利于实现p型特性.因此, Te-N共掺有望成为一种更为有效的p型掺杂手段.     

氮化铟p型掺杂的第一性原理研究

采用基于密度泛函理论(DFT)的总体能量平面波超软赝势法，对Mg，Zn，Cd掺杂InN的32原子超原胞体系进行了几何结构优化，从理论上给出了掺杂和非掺杂体系的晶体结构参数，其中非掺杂体系的理论值与实验值符合很好. 计算了掺杂InN晶体的结合能，总体态密度、集居数，差分电荷密度，并对此做了细致的分析. 计算结果表明，相对于Zn和Cd，Mg_In在InN中的溶解度会更大，并能提供更多的空穴态，非常有利于InN的p型掺杂. 关键词： 氮化铟 p型掺杂 电子结构 第一性原理     

温度对Al0.5Ga0.5As/AlAs分布布喇格反射器的反射谱影响

采用光学传输矩阵理论对Al0.5Ga0.5As/AlAs材料分布布喇格反射器(DBR)进行理论研究,分析了－10℃到100℃的范围内,温度变化对不同DBR结构的反射光谱影响.结果表明：随着温度的升高,传统20周期DBR的反射光谱向长波长方向移动,速率约0.05 nm/℃,其中由线热膨胀系数带来的影响小于0.001 nm/℃.当传统DBR的周期数增大时,温度对DBR光谱反射率的影响在减小,同时DBR的反射谱峰值波长发生红移.为了降低温度对DBR反射光谱的影响,提出一种新型的复式DBR结构.分析指出：该复式DBR比传统DBR有更大的反射光谱半峰宽,基本能覆盖同温度的AlGaInP LED电致发光光谱,这对提高LED的出光效率有现实意义.     

自成核对聚对苯二甲酸1,3-丙二酯结晶行为的影响

The effects of self-seeding nucleation on the crystallization behavior and properties of poly( trimethylene terephthalale) were studied. Differential scanning calorimetry (DSC) results indicated that the crystallization temperature of paly(trimethylene terephthalate) increased obviously(increased about 20℃) after the process of selfseeding nucleation. The results of polarized light microscopy (PLM) showed that the spherulite size decreased markedly from 40μm to 8μm.     

导电聚合物与锂二次电池

本文对聚合物的锂二次电池原理，发展、应用前景及今后的展望做了评述．     

聚丁二烯~(13)C-NMR谱图中一个新的共振吸收峰(T_4)

<正> 最近解析锂系和铁系含乙烯基聚丁二烯的~(13)C-NMR谱图,发现并确认了一个新的共振吸收峰。即聚丁二烯反式1,4-序列的第四峰,简称T_4峰。 Furukawa等对钼系和章哲彦等对铁系等二元聚顺-1,4-1,2-丁二烯的研究都指出在聚丁二烯的~(13)C-NMR谱图上,有四个谱峰属于顺1,4-序列。本文给出其化学位     

CaBPO5：RE（RE=Eu，Tb）的水热合成及其发光特性

利用水热法合成了CaBPO5：RE(RE=Eu，Tb)荧光体并测试了其结构和光谱，讨论了其发光性质，并与高温固相法合成的产物作了对比．结果表明，由于电子转移。Eu^3 ,Tb^3 和Eu^2 共存于同一体系中，而且Eu^2 的发射位置从402nm移至428nm,在双掺杂体系中引入Ce^3 ．Eu^3 ，Tb^3 和Eu^2 的发光强度均有所增强,这可能是Ce^3 与Eu^3 之间的电子转移及各种稀土离子之间能量传递相互竞争的结果。