Micro-Photoluminescence Investigation of Single Quantum Dot and its Molecule of CdSe/ZnSe

The single and a few coupled quantum dots are important for future quantum information sciences and their investigation is also a big challenge in physics. We investigate here the electronic and exciton states and their interaction with each other via micro photoluminescence. The luminescence for single and a few dots as well as a dot molecule of CdSe/ZnSe are measured with very high resolution, under liquid He temperature and magnetic fields and with different polarization of excitation laser. The observed sharp spectral lines are attributed to the atomlike transitions of exciton, trion, biexciton… in the investigated single QD or QD molecule. Band filling, Zeeman splitting, spin transition and their relaxation are observed and investigated＇from the spectra and compared with those of same material in different dimensions, and compared with the primary calculation as well. In addition, quite a few new phenomena, which can not be understood based on our present model and knowledge, are also observed; and some very interesting problems are left for further investigation.     

PVK∶DBVP掺杂体系的能量转移及发光性质的研究

研究了不同比例的PVK与齐聚PPV衍生物DBVP掺杂体系的能量转移和发光特性.通过对PVK,DBVP及PVK:DBVP掺杂体系的UV-vis,PL和PLE光谱的研究,分析了PVK与DBVP之间的能量转移过程.利用PVK在体系中类似于溶剂的分散作用,制备了结构为ITO/PEDOT/PVK:DBVP/LiF/Al的电致发光器件,研究了掺杂体系的电致发光性能.结果表明,在掺杂体系的光致发光和电致发光中,PVK的发射被有效地抑制,PVK与DBVP之间发生了非常有效的能量转移,通过调节PVK与DBVP的比例,可以获得蓝色和绿色发光,同时可以改善器件的发光性能,当PVK与DBVP的重量比为1∶2时,器件的绿色发光效率达到1·06cd/A,此时发光亮度为52cd/m2.     

SiOx纳米管的制备及其发光特性

以液态金属镓为媒介,利用热蒸发法合成大量非晶SiOx纳米管,这些纳米管管径均匀分布,平均约80 nm,长度大于10μm,且管内外径比例较小．分析发现,在实验过程中,熔入金属镓液滴中的硅元素和氧元素结合并从液滴的表面饱和析出,形成以镓为中心的非晶SiOx纳米管状结构．在室温中,利用260 nm的激发光源激发SiOx纳米管,发现在蓝光波段附近发出强而稳定的PL谱线,这可能与样品中的氧缺陷和空位有关．     

ZnSe及ZnSe/GaAs异质结构中压力导致的直接禁带向间接禁带的转变

用经验赝势方法计算了体ZnSe以及ZnSe/GaAs单异质结系统中ZnSe外延层г、X、L等特殊对称点导带底能量随压力的变化。结果表明，同Si、Ge、GaAs等半导体材料不同，ZnSe的X点导带底具有正的压力系数，但比г点的压力系数小，这是ZnSe材料以及ZnSe基异质结构材料发生直接禁带向间接禁带的转变时所需转变压力较大的根本原因。研究了ZnSe/GaAs异质结构中晶格失配造成的应变对外延层г、X、L对称点压力系数的影响，表明这种晶格失配造成的应变可以极大地减小ZnSe外延层材料由直接禁带向间接禁带的转变压力。     

一种有机电致发光共聚物的制备和性能

采用Suzuki方法合成了9，9-二辛基芴与萘并硒二唑的两种无规共聚物并研究了其紫外光谱、光致发光和电致发光性能。两种聚合物的电致发光波长为650～666nm，均为发饱和红光的LED材料，其电致发光外量子效率最高达到了1．05％。随着共聚物中萘并硒二唑含量的增加，共聚物的光致发光和电致发光的发射波长均有少量红移。证明了根据共轭高聚物链内能量转移原理，在聚芴链中引入不同含量的窄带隙杂环单元可实现对聚芴发光颜色的调节。     

Ga1-xInxAs/InAsyP1-y/InP异质结的MOCVD生长及表征

Ga1-xInxAs(x>0.53)材料是未来长距离低损耗光纤通信的理想光源材料和探测器材料之一.我们采用水平常压MOCVD系统,在InP衬底上成功地生长了Ga1-xInxAs(x>0.53)/InAsyP1-y/Inp异质结材料.其中InAs1-yPy为组份阶梯变化的多层结构.由样品的(400)面X光衍射结果测定了各层组份.由二次离子质谱(SIMS)得到了样品剖面组份变化结果,证明InAs1-yPy层组份为阶梯状变化的.通过对光致发光结果和X光衍射结果比较,可以看到,InAsyP1-y层通过位错和弹性畸变二种方式来释放或积累Ga1-xInxAs与InP间的失配应力,从而减少了Ga1-xInxAs中的失配位错.有效地改善了Ga1-xInxAs的质量.已获得了x高达0.94表面光亮的Ga1-xInxAs/InAs1-yPy/InP异质结材料.     

Time—Resolved Photoluminescence Studies of AlInGaN Alloys

We study the two samples of AlInGaN,i.e.,1-μm Gan grown at 1030℃ on the buffer and followed by a 0.6μm-thick epilayer of AlInGaN under the low pressure of 76 Torr and the AlInGaN layer deposited diectly on the buffer layer without the high-temperature GaN layer,by temperature-dependent photoluminescence(PL) spectroscopy and picosecond time-resolved photoluminescence(TRPL) spectroscopy.The TRPL signals of both the samples were fitted well as a stretched exponential decay at all temperatures,indicating significant disorder in the material.We attribute the disorder to nanoscale quantum dots or discs of high indium concentration.Temperature dependence of dispersive exponent β shows that the stretched exponential decay of the two samples comes from dfferent mechanisms.The different depths of the localization potential account for the difference,which is illustrated by the results of temperature dependence of radiative recombination lifetime and PL peak energy.     

Modified Photoluminescence by Silicon-Based One-Dimensional Photonic Crystal Microcavities

photoluminescence (PL) lrom one-dimensional photonic band structures is investigated. The doped photonic crystal with microcavitles are fabricated by using alternating hydrogenated amorphous silicon nitride (a-SiNx:H/a-SiNy:H) layers in a plasma enhanced chemical vapour deposition (PECVD) chamber. It is observed that microcavities strongly modify the PL spectra from active hydrogenated amorphous silicon nitride (a-SiNx:H) thin film. By comparison, the wide emission band width 208nm is strongly narrowed to 11 nm, and the resonant enhancement of the peak PL intensity is about two orders of magnitude with respect to the emission of the λ/2-thick layer of a-SiNx:H. A linewidth of Δλ=11 nm and a quality factor of Q=69 are achieved in our one-dimensional a-SiNz photonic crystal microcavities. Measurements of transmittance spectra of the as-grown samples show that the transmittance resonant peak of a cavity mode at 710nm is introduced into the band gap of one-dimensional photonic crystal distributed Bragg reflector (DBR), which further verifies the microcavity effects.     

测试温度对nc-Si∶H膜光致发光特性的影响

利用常规等离子体化学气相沉积（ＰＥＣＶＤ）工艺制备了ｎｃ－Ｓｉ∶Ｈ膜，并对其光致发光（ＰＬ）特性从１０～２５０Ｋ温度范围内进行了变温测量．实验结果指出，随着测试温度升高，ＰＬ峰值能量发生了５４ｍｅＶ的红移，ＰＬ强度在Ｔ＞８０Ｋ后呈指数下降趋势．ＰＬ峰值能量的红移起因于带隙的收缩，而ＰＬ强度的减弱则是由于非辐射复合起了主导作用．