Influence of Intercalated Li on Electronic Structures and Optical Properties of V_2O_5

采用第一性原理局域密度近似法计算了V2O5的电子态密度和能带结构以及Li嵌入后对其电子结构和光学性质的影响。计算结果表明,V2O5是间接带隙半导体,Li的嵌入并没有改变其电子的跃迁方式。但Li的嵌入使得V2O5导带能量下移,禁带宽度减小,导带中原有的劈裂被分裂的能级填满;同时致使价带出现展宽。电子态密度计算结果表明Li的嵌入对临近的O和V的电子结构有较大的影响。Li2s电子的注入提高了V2O5的费米能级并导致其进入导带。由于价带中的电子只能跃迁到费米能级以上的导带空能级,这致使体系实际的光学带隙增大。同时随着Li注入量的进一步增加,价带的展宽更为明显,费米能级亦呈升高的趋势,使得光学带隙随着Li注入量的增加而增大。The density of states and band structures of α-V2O5 and Li-intercalated V2O5 (LixV2O5, x= 0.5 and 1.0) have been studied using a first-principles calculation based on density function theory with the local density approximation. The results indicate that V2O5 is an indirect-gap semiconductor; the intercalation of Li will not change its way of electron transition. While, the intercalation of Li lowers the energy of conduction band, and then narrows the band gap. At the same time, due to the intercalation of Li, the split-off in the conduction band of V2O5 disappears because of the split of conduction band. The Fermi level of LixV2O5 increases dramatically due to the electron transfer from Li 2s to the V2O5 host, which is probably the main reason why the optical band-gap augments with the Li intercalation.国家重点基础研究发展规划(001CB610505);; 国家自然科学基金(60376015,60336020);; 福建省青年人才创新基金(2005J005)资助项目~

MOCVD growth of high-reflectivity AlN/GaN distributed Bragg reflectors

利用金属有机物化学气相沉积(MOCVD)方法在蓝宝石c面衬底上制备出高反射率AlN/GaN分布布拉格反射镜(DBR)。利用分光光度计测量,在418 nm附近最大反射率达到99%。样品表面显微照片显示,有圆弧形缺陷和少量裂纹出现;在缺陷和裂纹以外的区域,DBR具有较为平坦的表面,其粗糙度在10μm×10μm面积上为3.3 nm左右。样品的截面扫描电镜(SEM)照片显示,DBR具有良好的周期性。对反射率和表面分析的结果表明,该样品达到了制备GaN基垂直腔面发射激光器(VCSEL)的要求。A high reflectivity AlN/GaN distributed Bragg reflector(DBR) is grown on c-plane sapphire substrate by metalorganic chemical vapor deposition(MOCVD).A peak reflectivity of 99% is observed around 418 nm by spectrophotometer.Compass-shape defects and a few cracks are observed on the surface.The surface root mean square(RMS) of roughness in the flat area is around 3.3 nm over a 10 μm×10 μm area.The cross-sectional scanning electron microscope(SEM) image reveals the good periodicity of DBR.Considering the peak reflectivity and surface morphology,the DBR can be used to fabricate GaN-based vertical cavity surface emitting laser(VCSEL).国家高技术研究“863”计划资助项目(2006AA03Z409

DX CENTERS IN Te-DOPED GaAsP ALLOYS

用高分辨率深能级瞬态谱、光照深能级瞬态谱及光电容谱方法,对不同组份的掺TE的gAASP混晶进行了实验研究,结果表明,所有被测样品中同时存在三种施主深能级,其热发射激活能各为0.18,0.28,0.38EV.通过仔细测量与分析它们的电学和光学性质后,认为它们是由TE施主杂质形成的三种类dX中心,可能对应于TE运动会替位施主的不同原子构形.We used high-resolution DLTS, illumination DLTS and photocapacitance spect-rascopy to study Te-doped GaAs1-xPx alloys with diFFerent compositions and observed the simultaneous existence of three kinds of deep donor levels with thermal activa.ion energies of 0.18,0.28,0.38eV respectively.AFter deta iled measurements and analyses on these deep levels, it was reasonable to consider that they may be three Te-related DX-like centers and correspond to diFFerent atom conFigurations.国家自然科学基金;红外物理国家重点实验室资助的课题

太阳能电池有机电子传输材料研究新进展

当今能源危机问题日益紧迫,以太阳能为代表的新能源开发成为研究热点。有机半导体材料具有成本低廉、可塑性强、性能优异等特点,因此在太阳能电池领域中具有极大的应用前景。研发性能优异、成本低、稳定性高的有机电子传输材料是太阳能电池研究领域的重要内容。总结了近年来有机电子传输材料的研究进展和发展方向,按照其分子结构分为富勒烯衍生物、大π共轭体系、非π体系、改性材料、碳纳米材料等5类体系,分别介绍了其结构特性,讨论了其在太阳能电池应用中存在的问题及解决方法,综述了该领域的最新研究成果,最后总结了开发新型高效的有机电子传输材料的研究方向

New Research Progress of Organic Electron Transport Materials in Solar Cells

The development of new energy, which is represented by solar energy, has become a research hots- pot as the energy ciisis is becoming more and more urgent nowadays. Organic semiconductor materials are of great potential and prospect in the field of sola

Semiconductor-Optoelectronic Structural Materials and Their Applications

半导体光电结构材料广泛应用于信息、照明、交通、能源、医疗、军事等领域.介绍了厦门大学近年来在半导体光电结构材料研究的进展,着重介绍高Al组分AlgAn、高In组分IngAn、gAn基半导体、SI基半导体、znO基半导体等结构材料研发中所取得的进展及其在大功率lEd、紫外lEd、激光器、探测器、太阳能电池等光电器件中的应用.The semiconductor-optoelectronic structural materials are widely used in information,lighting,transportation,energy,medical,military and other fields.In this paper,we present the recent developments in Xiamen University about some structural semiconductor materials and their applications in high-power LEDs,UV LEDs,lasers,detectors,solar cells and other optoelectronic devices.国家重点基础研究计划(973)项目(2011CB925600;2011CB301905;2007CB613404);国家高技术研究发展计划(863)项目(2006AA03A110;2006AA03Z409);国家自然科学基金项目(90921002;60827004;60837001;61076084;91023048;60876008

新疆油田准噶尔盆地复杂地质条件深井、超深井钻井技术

该课题针对准噶尔盆地的地质条件，形成了“地层孔隙压力检测预测综合应用”等十多项实用技术及相关软件，包括提高预探井地层孔隙压力、破裂压力和坍塌压力的预测、检测精度；提高地应力分布规律及对井壁稳定影响的机理及对策；钻头合理选型及钻进配套工艺；深井陡构造高效防斜技术；深井复杂情况及事故的预测及处理技术；高温、高压、高密度钻井液性能稳定性技术；提高低压易漏长封固段固井、高温高压气井固井技术；高扭距涡轮节、长寿命轴承组可靠性分析。该项目提高了新疆油田准噶尔盆地复杂地质条件深井、超深井钻井技术水平，促进了准噶尔盆地腹部和南缘山前构造带的勘探步伐，提高了综合经济效益