排序方式: 共有24条查询结果,搜索用时 15 毫秒
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中孔MCM—41分子筛在微孔沸石ZSM—5上附晶生长的研究 总被引:15,自引:2,他引:15
首次在微孔沸石ZSM5表面进行了MCM41分子筛的附晶生长,并首次提出中孔材料MCM41分子筛静电组配理论的新形式(XS+I);同时利用XRD、TEM、BET等测试手段表征了合成样品,并讨论了微孔沸石表面附晶生长中孔分子筛MCM41的合成化学,考察了F离子效应、pH值及表面活性剂CTAB(十六烷基三甲基溴化铵)的影响。 相似文献
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文章首先介绍了发光二极管(LED)的内量子效率、外量子效率的基本概念和提高量子效率的基本方法,接着对LED外延的结构和方法做了简要介绍.文章的第三和第四部分则着重介绍了提高内、外量子效率的外延方法,这些方法包括外延结构的优化,侧向外延生长,SiC和GaN衬底的生长,AlInGaN四元系有源区生长,非极性面、半极性面的外延,表面粗化结构生长,图形化二次外延结构.图形化蓝宝石衬底上的外延,提高载流子注入效率的结构和组分设计.文章的第五部分则介绍了基于可靠性和成本考虑的其他新型外延结构,第六部分介绍了提高LED 相似文献
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高亮度白光LED用外延片的新进展 总被引:5,自引:0,他引:5
文章首先介绍了发光二极管(LED)的内量子效率、外量子效率的基本概念和提高量子效率的基本方法,接着对LED外延的结构和方法做了简要介绍.文章的第三和第四部分则着重介绍了提高内、外量子效率的外延方法,这些方法包括外延结构的优化,侧向外延生长,SiC和GaN衬底的生长,AIInGaN四元系有源区生长,非极性面、半极性面的外延,表面粗化结构生长,图形化二次外延结构.图形化蓝宝石衬底上的外延,提高载流子注入效率的结构和组分设计.文章的第五部分则介绍了基于可靠性和成本考虑的其他新型外延结构,第六部分介绍了提高LED可靠性的外延方法.最后得出结论:采用非极性面的GaN衬底,生长优化的LED结构,并结合光子晶体技术,可望取得突破性进展. 相似文献
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R. Schuster H. Hajak M. Reinwald W. Wegscheider D. Schuh M. Bichler G. Abstreiter 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):236
The confinement energy of T-shaped quantum wires (QWRs), which were fabricated by the cleaved edge overgrowth technique in a way that the QWRs form at the intersection of In0.2Al0.8As stressor layers and the overgrown (1 1 0) GaAs quantum well (QW), is examined using micro-photoluminescence spectroscopy. Photoluminescence (PL) signals from individual QWRs can be spatially resolved, since the strained films are separated by 1 μm wide Al0.3Ga0.7As layers. We find that due to the tensile strain being transmitted to the QW, the confinement energy of the QWRs rises systematically up to 40 meV with increasing thickness of the stressor layers. By reducing the excitation power to 0.1 μW the QWR PL emission occurs 48 meV redshifted with respect to the QW. All QWR peaks exhibit smooth lineshapes, indicating the absence of pronounced exciton localization. 相似文献
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N. Usami J. Arai E. S. Kim K. Ota T. Hattori Y. Shiraki 《Physica E: Low-dimensional Systems and Nanostructures》1998,2(1-4)
Two approaches to control the position and the size of semiconductor islands are proposed. The first method is to perform overgrowth on a cleaved edge of strained multiple quantum wells which acts as a substrate with a periodically modulated lattice constant, thus inducing a periodic strain to the overgrown layer. The second method is to selectively grow islands in specific windows defined by electron beam lithography. Both the methods are applied to the Ge/Si system and the controllability of the Ge island formation is demonstrated. 相似文献
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Martina Hribova Frantisek Rybnikar Jarmila Vilcakova 《Journal of Macromolecular Science: Physics》2013,52(1):16-25
Microscopical, differential scanning colorimetry (DSC), and X-ray structural investigations of solution crystallized carbon nanotube (CNT) composites with linear polyethylene (LPE), isotactic polypropylene (iPP), polybutene-1 (PB-1), and nylon 6 (PA6) disclosed varying degrees of surface interaction and nucleation effect of CNT in these polymers and formation of oriented shish-kebab overgrowths on the CNT ropes in LPE and PA6. The character of the attraction and orientation forces at the CNT-polymer interface is discussed. 相似文献
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A. Wierzbicka J. Z. Domagala M. Sarzynski Z. R. Zytkiewicz 《Crystal Research and Technology》2009,44(10):1089-1094
Spatially resolved X‐ray diffraction (SRXRD) is applied for micro‐imaging of strain in laterally modulated epitaxial structures. In GaAs layers grown by liquid phase epitaxial lateral overgrowth (ELO) on SiO2‐masked GaAs substrates a downward tilt of ELO wings caused by their interaction with the mask is observed. The distribution of the tilt magnitude across the wings width is determined with μm‐scale spatial resolution. This allows measuring of the shape of the lattice planes in individual ELO stripes. If a large area of the sample is studied the X‐ray imaging provides precise information on the tilt of an individual wing and its distribution. In heteroepitaxial GaSb/GaAs ELO layers local mosaicity in the wing area is found. By the SRXRD the size of microblocks and their relative misorientation were analyzed. Finally, the SRXRD technique was applied to study distribution of localized strain in AlGaN epilayers grown by MOVPE on bulk GaN substrates with AlN mask. X‐ray mapping proves that by mask patterning strain in AlGaN layer can be easily engineered, which opens a way to produce thicker, crack‐free AlGaN layers with a higher Al content needed in GaN‐based laser diodes. All these examples show that high spatial and angular resolutions offered by SRXRD makes the technique a powerful tool to study local lattice distortions in semiconductor microstructures. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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C.X. Cui Y.H. Chen C.L. Zhang P. Jin G.X. Shi Ch. Zhao B. Xu Z.G. Wang 《Physica E: Low-dimensional Systems and Nanostructures》2005,28(4):537-544
A novel method for positioning of InAs islands on GaAs (1 1 0) by cleaved edge overgrowth is reported. The first growth sample contains strained InxGa1−xAs/GaAs superlattice (SL) of varying indium fraction, which acts as a strain nanopattern for the cleaved-edge overgrowth. Atoms incident on the cleaved edge will preferentially migrate to InGaAs regions where favorable bonding sites are available. By this method InAs island chains with lateral periodicity defined by the thickness of InGaAs and GaAs of SL have been realized by molecular beam epitaxy (MBE). They are observed by means of atomic force microscopy (AFM). The strain nanopattern's effect is studied by the different indium fraction of SL and MBE growth conditions. 相似文献