259 resultados para 331.8


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本论文以提高有机/聚合物电致发光材料的发光效率为目的,通过改善发光材料分子的载流子传输平衡、增大分子体积为手段来减小荧光淬灭,设计并合成了一系列新型结构的络合物和聚合物。发现了一种合成五配位8-轻基喳琳铝络合物和双核铝8-轻基喳琳络合物的新方法,在分子中引入了电子和空穴传输基团改善了分子的载流子传输平衡,设计并合成了新型大体积的分子,提高了材料的发光效率,并系统地研究了分子结构与发光波长和发光效率的关系。主要工作如下:1发现了一种合成五配位8-经基喳琳铝络合物和双核铝8-经基喳琳络合物的新方法,克服了没有2一甲基的空间位阻作用很难形成五配位8-轻基喳琳铝络合物的困难。2合成了五配位2-甲基-8-轻基喳琳铝络合物并引入了具有不同空穴传输能力的第二配体。结果表明,与A 1 q;,相比,2-甲基-8-经基喳琳的引入导致了五配位络合物发光的蓝移,同时具有空穴传输能力的三苯胺基团的引入使电致发光器件的效率降低。3设计并合成了五配位8-轻基喳琳铝络合物,同时与Alq做了对比研究。研究发现,这一系列五配位络合物发射绿色荧光,五配位8-轻基喳琳铝络合物的发光波长主要由第一配体决定。4以五配位2-甲基-8-轻基喳琳铝和五配位8-轻基喳琳铝络合物为发光层制备了双层器件。结果表明,五配位8-经基喳琳铝络合物的电致发光波长主要由第一配体决定,第二配体只起到微弱的调节作用;第一配体对器件的发光效率起决定性的作用,第二配体的结构对络合物器件发光效率的影响在同一系列络合物中表现得非常明显。5从增加分子体积能够减小分子之间聚集,增强荧光效率这一观点出发,合成了具有双核铝的8一TTA-基喳琳络合物Me-DAlqz和PPv-DAlq3,用Me-DAlq,作发光层制备了双层器件,并与Alq_3i和AIMq_3作了对比研究。结果表明,DA 1 q,双层器件中的发光效率比Alq_3器件的性能稍高一些,证明了大体积分子能够增加荧光效率的观点。6合成了含有空穴传输性能的三苯胺基团的嗯二吟配体,并用其合 成了金属络合物。这些络合物发射蓝色的荧光,与不带三苯胺的德二哇金属络合物在溶液中发基本相同波长的荧光。但在薄膜和单层电致发光器件中,络合物的荧光发生了不同程度的红移。含三苯胺络合物的单层器件发光效率高于不含三苯胺络合物的单层器件的效率,证实了三苯胺的引入改进了载流子的传输平衡。7合成了系列嗯二哇基团两侧带有蔡环的金属络合物并以这些络合物为发光层制备了双层有机电致发光器件。结果表明,蔡环的引入导致了嗯二哇金属络合物在薄膜状态和电致发光器件中的发光波长比在溶液中的发光波长有了很大的红移。8设计并合成了既具有空穴传输性能又具有电子传输性能的蓝色发光聚合物。用电化学方法证明了它们具有两极性质,表明嗯二哇的引入增加了聚合物的电子传输能力。

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AAO模板具有高度有序的纳米孔阵列,其孔径可以在5一200nm范围内调节,利用AAO模板进行纳米组装已成为纳米结构材料组装的重要技术之一。目前,采用该技术已经制备出了金属、半导体、碳、导电高分子以及其它材料构成的纳米管、纳米线、纳米纤维、电缆等纳米结构单元和有序纳米阵列材料,同时,研究了它们的光、电、磁和催化等特性及其在光学材料、铿电池的电极材料、垂直磁性记录材料和光催化剂等方面的潜在应用。然而,有关稀土发光材料的AAO模板合成及其性质还鲜见报道。本论文采用二次阳极氧化技术制备出了具有高度有序纳米阵列孔的AAO模板。采用溶胶一凝胶法和水热法对稀土发光材料M2O3:RE3+(M=Y,Gd; RE=Eu,Tb)体系进行了AAO组装,得到了纳米线、纳米管及其纳米线阵列。对AAO模板和组装样品的形貌、结构和光谱性质进行了表征,得到了一些令人感兴趣的研究结果,其主要的结果和结论总结如下:(1)采用二次阳极氧化法制备出了孔径约为5Onm、35nm和2Onm等系列高度有序纳米阵列孔的基体铝支持的AAO模板和独立支撑的AAO模板。(2)XRD测试结果表明:退火后的基体铝片,其331晶面优先结晶生长,这有利于高度有序纳米阵列孔AAO模板的制备。使用这些退火后的铝片,通过二次阳极氧化法制备的高度有序纳米阵列孔AAO膜为非晶态,并且在退火后转变为γ-Al2O3。(3)未退火的基体铝支持的AAO模板,在350一600nm范围内发出较强的蓝光,其峰值波长位于435nm。该蓝光发射带经过程序控温慢慢退火后完全消失,这说明它产生于缺陷发光中心。(4)采用溶胶一凝胶法,利用AAO模板首次合成出了(YO.96RE0.05)O3(RE=Eu,Tb)纳米线及其阵列,并通过SEM、EDX、TEM、SAED、XRD和PL分析测试加以确认。x-射线衍射(XRD)和选区电子衍射(SAED)的结果证明,这些纳米线主要是由立方相的RE2O3(RE=Y或Gd)多晶材料组成的。光谱测试结果表明,同体相材料相比,Eu3+的,D0一7F2跃迁发射峰和Tb3+的5D4一7FJ(J=6,5,4,3)跃迁发射峰出现了宽化,这种现象可能是纳米颗粒的表面界面效应所引起的非均匀宽化造成的。(5)首次观察到利用溶胶一凝胶法组装的一部分M2O3:RE3+(M=Y,Gd;RE=Eu,Tb)样品,沿着AAO模板阵列孔壁的边沿所形成的网状结构,并初步地探讨了其形成的机理。(6)对于M2O3:RE3+(M=Y,Gd;RE=Eu,Tb)体系,仅仅依靠毛细作用是难以充分地将溶胶前驱液组装进从O模板的阵列孔中。(7)首次利用水热合成法,在中性条件介质下,将(Y,Gd)2O3:Eu3+样品充分地组装进了AAO模板的纳米孔道中,这说明水热产生的高压可以作为AAO模板组 装样品的驱动力。(8)以M2O3: RE3+(M=Y,Gd;RE=Eu,Tb)溶胶或氢氧化物沉淀作为前驱物,分别在酸性和碱性条件下,进行了从0模板水热合成组装。实验结果表明,AAO模板被部分地损坏。但在碱性条件下的高压釜中,却得到了单晶纳米管、纳米片和纳米棒。

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Samples with different weight ratio of Se to zeolite 5A (Se concentration) have been prepared by loading Se into the pores of zeolite 5A, and the measuerments of the absorption and Raman spectra have been carried out for the prepared samples. The measured absorption edges of the samples are close to the value for monoclinic Se containing Se-8-ring, suggesting the formation of Se-8-ring clusters(1) in the pores. The continuous and broadening features of the absorption spectra are interpreted by the strong electron-nucleus coupling in the Se-8-ring cluster. The absorption edges are red shifted with the increase of the Se concentration. It is tentatively attributed to two reasons. One is the existence of the double Se-8-ring cluster in the high Se concentration samples, and the other is that for the strong electron-nucleus coupling cluster, the absorption edge of the clusters system will be red shifted with the increase of the cluster concentration in the clusters system. A single broad band at about 262 cm(-1) is observed in the Raman spectra, which further supports the formation of Se-8-ring clusters. (C) 1997 Published by Elsevier Science S.A.

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By considering all possible high order diffracted waves, the authors investigate the spectral response of two-dimensional gratings for quantum well infrared photodetectors (QWIPs). A new method is proposed that using long period gratings may improve grating quality and reduce the resulting cross talk in grating-coupled QWIPs. A sensitivity analysis indicates that the influence of variation of the grating constant on the coupling efficiency is less sensitive for the long period gratings than for the short ones. A large coupling efficiency has been demonstrated for long period gratings. The calculated wide grating response spectra are in good agreement with the experiment result. (C) 1996 American Institute of Physics.

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Samples with different weight ratio of Se to zeolite 5A (Se composition) have been prepared by loading Se into the cages of zeolite 5A and the measurements of the absorption and Raman spectra have been carried out for the prepared samples. The measured absorption edges of the samples close and blue shifted to the value for monoclinic Se containing Se-8-ring, suggesting the formation of Se-8-ring clusters dagger in the cages. The continuous and broadening features of the absorption spectra are interpreted by the strong electron-phonon coupling in Se-8-ring clusters. The sample with high Se composition has a red shift of the absorption band edge relative to the samples with less Se composition. It is tentatively attributed to the reason that with different Se composition, single Se-8-ring clusters and double Se-8-ring clusters are formed in the cages of zeolite 5A. A single broad band at about 262 cm(-1) is observed in the Raman spectra, that gives the further support of the formation of Se-8-ring clusters. Copyright (C) 1996 Elsevier Science Ltd

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Step like morphology of (331)A high-index surfaces during atomic hydrogen assisted molecular beam epitaxy (MBE) growth has been investigated. Atomic Force Microscope (AFM) measurements show that in conventional MBE, the step heights and terrace widths of GaAs layers increase monotonically with increasing substrate temperatures. The terrace widths and step densities increase with increasing the GaAs layer thickness and then saturates. And, in atomic hydrogen assisted MBE, the terrace width reduces and density increases when depositing the same amount of GaAs. It attributes this to the reduced surface migration length of Ga adatoms with atomic hydrogen. Laterally ordered InAs self-aligned nano-wires were grown on GaAs (331)A surfaces and its optical polarization properties were revealed by photoluminescence measurements.

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采用分子束外延方法在CaAs(331)A高指数衬底上制备自对齐InAs纳米线(QWRs)或者三维(3D)岛状结构.InAs纳米线(QWRs)选择性生长在CaAs层的台阶边缘.通过原子力显微镜(AfM)仔细研究了InAs纳米微结构的表面形貌,发现不同的生长条件,包括:衬底温度、生长速率、和InAs层厚度等,对InAa表面形貌有很大的影响.如,低温更容易导致线状纳米微结构的形成,而高温更利于3D岛状结构形成.表面形貌的转变归结于表面能同应变能之间的竞争.

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用光荧光谱和原子力显微镜测试技术系统研究了在2 nm In0.2Ga0.8As和x ML GaAs的复合应力缓冲层上生长的InAs/GaAs自组织量子点的发光特性和表面形貌.采用In0.2Ga0.8As与薄层GaAs复合的应力缓冲层,由于减少了晶格失配度致使量子点密度从约1.7×109 cm-2显著增加到约3.8×109cm-2.同时,复合层也有利于提高量子点中In的组份,使量子点的高宽比增加,促进量子点发光峰红移.对于x=10 ML的样品室温下基态发光峰达到1350 nm.

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报道了基于应变补偿的InP基In0.53+xGa0.47-xAs/In0.52-yAl0.48+yAs分布反馈量子级联激光器.采用二级光栅作为反馈,激射工作波长为7.8μm,在1%占空比,5kHz频率的工作条件下,在93~173K的温度范围内,单模发射光谱边模抑制比均超过20dB,调谐系数dλ/dT=0.5125nm/K.在93K时,峰值功率为30mW,直到153K时,峰值光功率仍达到12mW.

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半导体材料开放实验室基金,国家自然科学基金

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We demonstrate surface emitting distributed feedback quantum cascade lasers emitting at wavelengths from 8.1 mu m at 90 K to 8.4 mu m at 210 K. The second-order metalized grating is carefully designed using a modified coupled-mode theory and fabricated by contact lithography. The devices show single mode behavior with a side mode suppression ratio above 18 dB at all working temperatures. At 90 K, the device emits an optical power of 101 mW from the surface and 199 mW from the edge. In addition, a double-lobe far-field pattern with a separation of 2.2 degrees is obtained in the direction along the waveguide.