纳米ZnO微晶的合成及其发光特性

以醋酸锌和尿素为主要原料,利用沉淀-水热法一步合成了纳米ZnO微晶。用XRD,TEM,FTIR等测试技术及光致发光光谱(PL)对纳米ZnO微晶进行了表征,并对其发光特性进行了分析。研究表明：该合成方法操作简单,得到的纳米ZnO颗粒基本无团聚,结晶性较好,平均粒径约为17.2 nm,并在500～750 nm范围内出现宽的PL峰, 呈现出纳米材料的发光特征。     

氧化锌纳米棒的生长过程研究

利用高分子聚乙烯吡咯烷酮(PVP)和乙酸锌的配合物作为前驱体,在300 ℃温度下煅烧,并制备了氧化锌纳米棒。生成的产物用XRD,TEM,SAED等测试方法进行了表征。为了研究氧化锌纳米棒的生长过程,我们通过控制制备前驱体所需原料的比例不变,改变在300 ℃温度下煅烧的时间,分别为0.5, 3, 12和24 h,来观察生成产物的形貌特征。实验发现在110 ℃温度下干燥的前驱体中已经有氧化锌微晶生成;在300 ℃温度下煅烧0.5 h后就出现了明显的由几个纳米大小的微晶所组成的氧化锌纳米棒;煅烧3 h后的产物是结构非常完整的径直单晶ZnO纳米棒;12和24 h煅烧前驱体生成的ZnO纳米棒长度有所增加,ZnO的量基本保持不变。实验发现氧化锌的生长是沿着c轴方向,但是在横向也有生长方向。     

不同溶胶体系对纳米氧化锌发光特性的影响

采用溶胶-凝胶工艺制备ZnO纳米粉体,研究了两种不同溶剂下制备的纳米ZnO的荧光特性。实验结果表明两种氧化锌样品有相同的晶型和能带结构,其紫外发光相似,但其带间的可见发射表现出了巨大差异,其原因在于两溶剂的极性不同导致两体系凝胶、烧结的微过程不同,从而使两种ZnO样品的表面态结构和布局发生变化。     

不同溶胶体系对纳米氧化锌发光特性的影响

采用溶胶-凝胶方法制备ZnO纳米粉体,研究了两种不同溶剂下制备的纳米ZnO的荧光特性。结果表明两种氧化锌有相同的晶型和能带结构,其紫外发光相似,但其带间的可见发射表现出了巨大差异,其原因在于两溶剂的极性不同导致两体系凝胶、烧结的微过程不同,从而使两ZnO样品的表面态结构和布局发生变化。     

电化学沉积法制备ZnO纳米柱及自驱动紫外探测性能研究

采用提拉法在ITO衬底上制备种子层,并使用电化学沉积制备高度取向的氧化锌纳米棒,研究了不同提拉次数下籽晶层厚度与电化学沉积电位对氧化锌纳米棒形貌的影响。在此基础上,制备了自驱动型紫外探测器并测试了其光响应谱。结果表明,该探测器可以对部分紫外波段(300~400 nm)有选择性地光响应,峰值响应度为0.012 A/W。     

Luminescence of ZnO nanopowders

The luminescence of ZnO nanocrystals prepared by different methods was studied under pulsed electron beam excitation. It is shown that the luminescence intensity depends on the nanocrystal sintering conditions and does not depend on the nanocrystal size within the range 10–50 nm. The relative luminescence intensities for the 3.32 eV (free exciton) and 3.20 eV (bound exciton) bands showed a dependence on nanocrystal size. The role of the nanocrystal surface in excitonic luminescence is discussed.     

生长温度对ZnO薄膜晶体质量和发光特性的影响

采用激光脉冲沉积法在Si(100)衬底上生长ZnO薄膜,衬底温度分别为室温,200℃,300℃,400℃和500℃.用X射线衍射仪、拉曼光谱、扫描电子显微镜对薄膜的微结构进行了测量,并测量了室温下薄膜的光致发光特性.结果表明,300℃时.ZnO具有最佳择优取向,随着衬底温度升高.衍射峰半峰全宽减小,薄膜晶粒尺寸增大,400℃时,薄膜具有各向等大的品粒尺寸.同时拉曼谱结果显示,薄膜内部的缺陷随衬底温度变化无明显差别,应力表现为张应力,400℃时应力最小,紫外发光峰在衬底温度为400℃时最强,而黄绿光带最弱.在减少薄膜缺陷,提高择优长向和晶粒尺寸的同时.使晶粒横向尺寸和纵向尺寸尽可能相同,可极大提高薄膜的发光特性.     

Fabrication and Photoluminescence Properties of ZnO Nanorods

ZnO nanorods are successfully synthesized by annealing the precursors in argon with the chemical precipitation method. The structural and optical properties of ZnO nanorods are investigated. As annealing temperature increases, the intensity of the green emission increases while the intensity of the yellow emission decreases. The result suggests that the green emission depends strongly on the annealing temperature.     

方位和品质对南疆果品空间特性光谱影响及反演方法研究

高光谱无损检测技术在果品定量无损检测中应用广泛,以冬枣、红提、香梨三种果品空间特性光谱为研究目标,探索空间特性光谱的影响因素和反演方法,为提高户外果品无损检测精度提供了一种新思路。分别提取三种果品的光谱库并计算空间特性光谱,依次使用马氏距离、浓度残差等预处理方法以及竞争性自适应权重取样算法选取特征波长,将处理后的三种果品空间特性光谱分别与品质（糖度、水分）和方位（探测角、方位角、相位角）建模,建模结果如下：三种果品（按照冬枣、红提、香梨的顺序）与糖分模型的相关系数r分别为：0.853 3,0.822 7和0.913 3;水分模型的相关系数r分别为：0.741 3,0.784 7和0.891 3;探测角模型相关系数r分别为：0.985 6,0.992 7和0.974 7;方位角模型相关系数r分别为：0.941 8,0.910 5和0.936 9;相位角模型相关系数r分别为：0.960 9,0.957 0和0.956 3。可以看出,不同果品方位模型相关性都明显高于品质模型相关性,因此方位因素是影响空间特性光谱的主要原因。使用Roujean模型和Walthall模型分别对不同方位的空间特性光谱进行反演,反演结果如下：使用Roujean模型反演三种果品（按照冬枣、红提、香梨的顺序）空间特性光谱时R2分别为0.934 4,0.928 1和0.830 6;r分别为0.990 2,0.983 9和0.969 1;RMSEP分别为0.030 9,0.048 7和0.062 7;平均模型误差分别为7.27%,11.02%和8.61%。使用Walthall模型描述不同果品空间特性光谱时R2分别为0.943 3,0.859 7和0.839 0;r分别为0.991 8,0.971 8和0.970 2;RMSEP分别为0.036 6,0.066 1和0.068 7;平均模型误差分别为6.19%,15.40%和7.84%。可以看出,Roujean模型可以很好的描述冬枣和红提的空间特性光谱,也可以较好的描述香梨空间特性光谱;Walthall模型可以很好的描述冬枣空间特性光谱,也可以较好的描述红提和香梨空间特性光谱。综上所述,在今后试验中可以使用Roujean模型反演红提和香梨的空间特性光谱,使用Walthall模型反演冬枣的空间特性光谱,进而提高户外果品户外果品无损检测精度。     

Luminescence anisotropy of ZnO microrods

The local features of light emission from ZnO microrods were studied: it is revealed that ZnO luminescence spectra are significantly influenced by the crystal morphology. It is shown that the near and edge ultraviolet emission occurs primarily from the top (0001) planes of ZnO microrods; while the defect related visible emission was found to occur dominantly from the side facets. The room temperature cathodoluminescence analysis revealed that visible emission consists of a few overlapping peaks, arising due to recombination on common points and surface defects (Zn_i, V_o, V_o⁰/V_o^?*_, V_o^** and surface defects.). While at low temperature, only the luminescence due to neutral donor bound exciton (D⁰X) emission is observed. The data obtained suggest that the light emission spectra of ZnO material of diverse morphology cannot be directly compared, although some common spectral features are present.     

ZnO纳米棒的拉曼和发光光谱研究(英文)

本文对采用湿化学方法合成的ZnO纳米棒样品的拉曼光谱和发光光谱进行了研究。由扫描电镜结果可知,合成的ZnO纳米棒具有很好的尺寸发布均匀性,直径在30 nm左右,长度大于1微米。采用显微拉曼光谱技术,得到了632.8 nm波长激发的拉曼光谱,并和体相样品的拉曼光谱进行了对比分析;由325 nm激光波长激发得到的荧光光谱可知样品具有很好的紫外发光性质。     

热蒸发法制备ZnO纳米棒阵列

氩气氛常压下，利用热蒸发法，在无催化剂、无ZnO预沉积层的硅衬底上制备了取向良好，排列整齐的ZnO纳米棒阵列．在距Zn源不同位置的Si衬底上得到了不同形貌的样品．硅衬底置于锌源正上方是得到取向一致的ZnO纳米阵列的一个关键性条件．用场发射扫描电子显微镜、X射线粉末衍射表征样品表面形貌、晶体结构．进一步研究了样品的生长机制和荧光性质．     

ZnO Nanorods Produced by the Method of Arc Discharge

ZnO nanorods are fabricated by arc discharge with ZnO powder as source materials. The sample is characterized by x-ray diffraction, Raman scattering spectra, scanning electron microscopy and high-resolution transmission electron microscopy. The ZnO nanorods exhibit single crystals with the hexagonal wurtzite structure. Many of them are tetrapod-like. The diameters range from several nanometres to about lOOnm, and the main diameters of the nanorods is around 20nm. The length-to-diameter ratio is more than 5, and the grown directions are along the [001] axis. Photoluminescence spectra show a narrow ultraviolet emission at around 389nm and a broad green emission at around 520 nm. The growth process can be interpreted by the vapour-solid mechanism.     

Luminescence enhancement of ZnO nanoparticles on metal surface

We have studied luminescence enhancement of zinc oxide (ZnO) nanoparticles with the average size of 30 nm on several metal surfaces at low temperatures. Bandedge luminescence originated from bound exciton (BE) annihilation is observed at 3.360 eV, and strongly depends on the kind and surface roughness of metal. The luminescence intensity is about 10 times larger for Ag surface than that for quartz surface. Furthermore, the luminescence increases remarkably when the roughness of Ag surface is almost the same as the particle size. The intensity ratio of the fast decay component to the slow one decreases for Ag surface compared with quartz. These results suggest that the luminescence enhancement is partially attributed to suppressing of the nonradiative recombination process in ZnO nanoparticles on metal surface.     

Photoinduced Effects in the ZnO Luminescence Spectra

The effect of intense UV irradiation on the photoluminescence (PL) spectra of ZnO powders and nanocrystalline films obtained by atomic layer deposition (ALD) was investigated. At room temperature, the behavior of the spectra under continuous UV irradiation in multiple vacuum-atmosphere cycles was studied. The changes in the intensities of exciton radiation and radiation in the “green” band region, associated with the phenomena of oxygen photodesorption and photoadsorption, are discussed. In the temperature range of 5–300 K, the effect of strong UV irradiation on the near-edge luminescence spectrum of ZnO films was studied. The nature of a new line arising in the photoluminescence spectra of an irradiated film in the region of emission of bound excitons is discussed.

     

Li掺杂ZnO纳米棒的导电和发光特性

利用气相输运方法,在(111)面硅衬底上制备了名义上原子数分数为2%的Li掺杂的ZnO纳米棒(样品A)。作为比较,我们在相同的生长条件下制备了没有任何掺杂的ZnO纳米棒(样品B)。XRD分析测试表明:样品A和样品B中的ZnO纳米棒具有纤锌矿六边形结构,没有其他氧化物,例如Li2O。Hall效应测量表明:样品A导电类型为p型,空穴载流子浓度为6.72×1016cm-3,空穴载流子迁移率为2.46 cm2.V-1.s-1。样品B为n型,电子载流子浓度为7.16×1018cm-3,电子载流子迁移率为4.73 cm2.V-1.s-1。低温光致发光光谱测试表明,样品A和样品B发光峰明显的区别是位于3.351 eV(样品B)和3.364 eV(样品A)处。根据文献报道,在没有掺杂的ZnO中,3.364 eV发光峰源于施主束缚激子发光。通过变温光致发光光谱的测试,证明了在样品A中,位于3.351 eV的发光峰源于受主束缚激子发光,其光学受主能级位于价带顶142meV处。     

Luminescence properties of Tb implanted ZnO

ZnO [0 0 0 1] crystals were irradiated at room temperature with Tb⁺ ions of 400 keV with fluences from 1×10¹⁶ to 2×10¹⁷ cm⁻². The implanted layer was examined by several methods, including radioluminescence (RL), Rutherford backscattering spectrometry (RBS) and optical spectroscopy. The optical extinction spectra were simulated using Mie scattering theory. Absorption spectra predicted by Mie theory for particles of decreasing diameter were compared with those obtained experimentally. Some qualitative agreement between theoretical and experimental data was achieved. It was also shown that the intensities of the characteristic green emission bands associated with Tb produced by ⁵D₄→⁷F_j=5,4 transitions have increased about 8 times after annealing. Optical spectroscopy and radioluminescence data have revealed that the ion implantation is a promising tool for synthesizing Tb nanoparticles in the ZnO surface. The Tb nanoparticles exhibit a rather weak plasma resonance.     

ZnO纳米棒／MEH-PPV异质结的复合电致隧穿发光

利用低温水热法生长的ZnO纳米棒（ZnO-NRs）,和p型有机半导体材料聚[2-甲氧基-5-（2-乙基己氧基）-1,4-苯撑乙烯撑]（MEH-PPV）复合制备了结构为“ITO/ZnO晶种/ZnO-NRs/MEH-PPV/Al”的发光器件。测试结果发现,该器件具有非常好的二极管整流特性。对ZnO-NRs/M EH-PPV异质结施加超过17 V的反向偏压时,可同时获得两种半导体材料的发光,且ZnO近紫外光（380 nm ）发射强度远大于 M EH-PPV的红橙光强度,发光功率随着反向偏压的增加迅速增强,然而施加正向偏压时未探测到发光。该器件的发光机理不同于其他文献报道的正偏压发光,而属于反偏压发光器件,其发光机理归因于有机无机复合异质结的界面特殊性和ZnO-NRs的纳米尺寸效应,反偏压下器件实现的是载流子隧穿发光,而正偏压时载流子以表面态的无辐射复合及漏电流方式消耗。