ZnO:Tb纳米晶的协同发光现象

用光致发光的方法研究了掺铽的ZnO纳米晶这种新型掺杂纳米晶体系,观察到了其中的协同发光现象,指出ZnO纳米基质与掺入其中的铽中心之间存在有效的能量传递.该能量传递对稀土铽离子的特征发光起决定性的作用. 关键词： 光致发光 掺杂 纳米晶     

基于MEH-PPV/ZnSe纳米复合器件的电致发光特性的研究

以巯基乙酸作为稳定剂在水相中制备了ZnSe纳米晶,用X射线粉末衍射(XRD)和X射线光电子能谱(XPS)对其进行了表征。用表面活性剂将ZnSe纳米晶从水相中转移到有机相中,使其与聚合物MEH-PPV复合作为发光层,制备了多层电致发光器件Glass/ITO/MEH-PPV∶ZnSe/BCP/Alq₃。对ZnSe纳米晶和MEH-PPV薄膜的光致发光谱及其吸收光谱的比较表明ZnSe纳米晶和MEH-PPV之间存在着能量传递,这是导致纳米复合薄膜的光致发光光谱和电致发光光谱存在差异的原因之一。文章对其在光激发和载流子注入条件下的不同发光机制进行了讨论。通过对器件的光电特性进行研究,发现ZnSe纳米晶发光的比例随着外加电压的增加而增加,而且器件的I-V特性基本上符合二极管的特性。     

巯基丙酸分子对CdSe核壳量子点和 ZnO纳米粒子薄膜之间电荷转移的影响

通过稳态光谱和时间分辨荧光光谱研究了巯基丙酸(MPA)分子对由量子点到ZnO纳米粒子薄膜的电荷转移过程的影响。研究发现,相对于CdSe纳米粒子薄膜样品,没有MPA分子参与作用的CdSe/ZnO薄膜样品和有MPA分子连接的CdSe/MPA/ZnO薄膜样品中都存在从CdSe量子点到ZnO纳米粒子薄膜的有效电荷分离过程,但是相对于CdSe/ZnO样品, CdSe/MPA/ZnO样品中电荷转移速率明显变小。这表明MPA分子本身它并不能促进CdSe到ZnO电荷分离过程,因此可以认为用金属氧化物薄膜直接吸附量子点吸收材料,将能获得高功率转换效率的量子点敏化太阳能电池。     

Zno纳米晶的室温紫外受激发射特征

ZnO的激子特性对制备氧化锌基的光电子器件至关霞要,因此对ZnO量子点中激子的发光性质及其跃迁过程进行研究显得十分必要.采用溶胶-凝胶法制备了ZnO纳米晶,X射线衍射(XRD)结果表明样品具有六角纤锌矿多晶结构.研究了在不同泵浦功率激发下ZnO纳米晶的紫外发射的时间积分光谱和时间分辨光谱,观察到自南激子发光,激子-激子碰撞和电子-空穴等离子体引起的受激发射,研究了在不同泵浦功率激发下自由激子及激子-激子碰撞随泵浦功率依赖的动力学过程.研究结果对理解激子带边发射有一定帮助,对ZnO材料在短波长半导体光电器件方面有潜在的应用价值.     

CdSe/CdS核/壳型纳米晶的光谱特性

以巯基乙酸为稳定剂制备了CdSe/CdS核／壳型纳米晶。用光吸收谱（Abs)、光致发光谱（PL）及光致发光激发谱（PLE）研究了CdS壳层对CdSe纳米晶电子结构，从而对其吸收和发光性能的影响。根据PL和PLE的结果以及带边激子精细结构的计算结果，我们用尺寸很小的纳米晶中所形成的基激缔合物解释了PL光谱与吸收边之间较大的Stokes位移。     

磁控溅射制备ZnO薄膜的受激发射特性的研究

用射频磁控反应溅射法在二氧化硅衬底上制备ZnO薄膜。得到了在不同温度下ZnO薄膜的吸收与光致发光。观测到了纵光学波 (LO)声子吸收峰与自由激子吸收峰 ;室温 (30 0K)下 ,PL谱中仅有自由激子发光峰。这些结果证实了ZnO薄膜具有较高的质量。探讨了变温ZnO薄膜的发光特性。研究了ZnO薄膜的受激发射特性。     

纳米ZnO薄膜对有机电致发光器件性能的影响

由于有机电致发光器件(Organic light-emitting devices,OLEDs)的主动发光、高亮度等优点,在显示和照明领域有极大的应用前景。报道了纳米ZnO薄膜对这种发光器件性能的影响。在普通有机电致发光器件空穴传输层和发光层之间直接蒸镀一层纳米ZnO薄膜,当纳米ZnO薄膜的厚度为1nm时,器件的电流效率可达3.26cd/A,是没有纳米ZnO薄膜同类器件的1.24倍。适当厚度的纳米ZnO薄膜降低了发光层空穴的浓度,提高了电子和空穴的平衡,从而提高了器件的效率。     

一种新的制备ZnO纳米粒子的方法--阴极电沉积法

用阴极电沉积法制备高质量ZnO纳米薄膜，电沉积采用含有不同浓度的ZnCl2的非水二甲基亚砜溶液做电解液，室温下恒流沉积，得到纳米ZnO薄膜。研究了ZnCl2浓度对薄膜结构和光学性质的影响。沉积薄膜的ZnO粒径尺寸分别为9．8，10．4，14．5nm。随着ZnCl2浓度的增加而增大。薄膜的可见光致发光谱以紫外的自由激子发射为主。研究表明：以浓度为0.03mol/L的ZnCl2电解液制备的ZnO薄膜光学性质最好。     

高质量ZnO及BeZnO薄膜的发光性质

用分子束外延设备插入缓冲层在c面蓝宝石上生长得到高质量ZnO和BeZnO薄膜。XRD测试显示薄膜具有六方结构和c轴取向,并具有良好的晶体质量,其中ZnO薄膜的半高宽仅为108 arcsec,Be_xZn_1-xO薄膜的半高宽小于600 arcsec。对ZnO和BeZnO薄膜的拉曼光谱进行对比研究发现,随着Be元素的掺入,A₁(LO)、A₁(2LO)声子模频率往大波数方向移动,并且首次发现了与Be元素掺杂有关的局域振动模。利用变温光致发光光谱研究了薄膜的发光性质,结果显示ZnO薄膜室温光致发光只出现一个紫外发发光峰(378 nm),而低温光谱(80 K)则出现了很强的自由激子发光峰。随着温度的升高,束缚激子发光逐渐湮灭向自由激子发光转变,并且峰值位置红移。相对于ZnO薄膜,BeZnO薄膜的紫外发光主峰位置蓝移,并且由于Be元素的掺入导致薄膜晶体质量下降,在低温(80 K)光致发光光谱中没有出现强的自由激子发光峰。另外,在低温光致发光及拉曼光谱中,主峰位置在100~200 K之间有局部最大值,推测为由于合金晶格热膨胀系数失配而引起的应力效应。     

MBE生长ZnO薄膜的结构和光学特性的研究

用等离子体源辅助分子束外延(P-MBE)方法在蓝宝石(0001)面上生长出了高质量的ZnO薄膜,并对其结构和发光特性进行了研究。在XRD中只观察到ZnO薄膜的(0002)衍射峰,其半高宽(FWHM)值为0.18°;而在共振Raman散射光谱中观测到1LO(579 cm-1 )和2LO(1 152 cm-1 )两个峰位,这些结果表明ZnO薄膜具有单一c轴取向和高质量的纤维锌矿晶体结构。在吸收光谱中观测到自由激子吸收和激子-LO声子吸收峰,这表明在ZnO薄膜中激子稳定的存在于室温,并且两峰之间能量间隔为71.2 meV,与文献上报道的ZnO纵向光学声子能量(71 meV)相符。室温下在光致发光光谱(PL)中仅观测到位于376 nm处的自由激子发光峰,而没有观测到与缺陷相关的深能级发射峰,表明ZnO薄膜具有较高的质量和低的缺陷密度。     

生长条件对Ga掺杂ZnO薄膜微观结构及光致发光性能的影响

利用热氧化法在不同参数条件下生长了Ga掺杂范围较宽的ZnO薄膜, 研究了ZnO薄膜的表面微观结构和光致发光性能. 研究表明: Ga以Ga³⁺存在并掺入ZnO晶格取代Zn²⁺, Ga的掺入改变了ZnO薄膜中的缺陷类型及浓度、化学计量比、薄膜表面结晶质量, 进而影响了薄膜的光致发光性能. 随着热氧化温度升高, Ga掺杂量增大, ZnO薄膜的晶粒尺寸增大, 尺寸更均一, 紫外光与可见光强度比增大. 随着热氧化时间延长, Ga掺杂量降低, ZnO薄膜的晶粒尺寸均一性变差, 紫外光与可见光强度比减小.     

退火温度对ZnO薄膜结构和发光特性的影响

采用反应射频磁控溅射法在 Si(100)基片上制备了高c轴择优取向的ZnO薄膜，研究了退火温度对ZnO薄膜的晶粒尺度、应力状态、成分和发光光谱的影响，探讨了ZnO薄膜的紫外发光光谱和可见发光光谱与薄膜的微观状态之间的关系.研究结果显示,在600—1000℃退火温度范围内，退火对薄膜的织构取向的影响较小，但薄膜的应力状态和成分有比较明显的变化.室温下光致发光光谱分析发现，薄膜的近紫外光谱特征与薄膜的晶粒尺度和缺陷状态之间存在着明显的对应关系；而近紫外光谱随退火温度升高所呈现的整体峰位红移是各激子峰相对比例变 关键词： ZnO薄膜 退火 光致发光 射频反应磁控溅射 可见光发射     

Photoluminescence enhancement from hybrid structures of metallic single-walled carbon nanotube/ZnO films

We investigated the dependence of localized surface plasmon resonance (LSPR) coupled photoluminescence (PL) emission on the density of a metallic single-walled carbon nanotube (m-SWCNT). The m-SWCNTs of various densities were deposited on top of ZnO films by spin coating and filtration transfer method to form the hybrid structures. We observed PL enhancement from ZnO films deposited with spin coated m-SWCNT, comparing with pure ZnO film. The m-SWCNT acts as absorbers for the light emitted due to SPR. After resonant excitation, hot electrons in m-SWCNT are created in high energy states, which can then transfer from the m-SWCNT to the conduction band of the ZnO films. We discuss the relationship between the hot electron flow generated by internal photoemission and LSPR.     

ZnO/Zn界面对纳米ZnO薄膜光学性质的影响

采用氧等离子体辅助电子束蒸发金属Zn后低温退火的方法制备纳米ZnO薄膜。利用X射线衍射(XRD)谱、拉曼(Raman)谱、X射线光电子能谱(XPS)以及光致发光(PL)谱等手段,分析了退火温度及ZnO/Zn界面对样品的结构和发光性质的影响。Raman结果表明随着退火温度的升高,界面模式(Es)振动减弱并向低波数方向移动。当退火温度为400℃时,界面振动消失,Zn全部转化成具有六方纤锌矿结构的ZnO,得到化学配比的纳米ZnO薄膜。PL谱表明,经400℃退火处理的样品紫外发射最强,发光性质最好。     

Influence of metallic coatings on the photoluminescence properties of ZnO nanowires

We report on low‐temperature photoluminescence studies of ZnO nanowires coated with thin metallic films. For all analyzed metals (Al, In, Au, Ni, Cu), we find an increased relative intensity of the green deep‐level emission. This is accompanied by a significant reduction of the relative intensity of the surface exciton band. The observed effects are most likely related to the formation of metal induced gap states in the surface region of the ZnO nanowires. A model for the band structure in the surface region of the metal‐coated nanowires is proposed that successfully explains the changes in the photoluminescence spectra after the coating process. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Controlling the energy transfer between near-field optically coupled ZnO quantum dots

We performed time-resolved spectroscopy of ZnO quantum dots (QD), and observed exciton energy transfer and dissipation between QD via an optical near-field interaction. Two different sizes of ZnO QD with resonant energy levels were mixed to test the energy transfer and dissipation using time-resolved photoluminescence spectroscopy. The estimated energy transfer time was 144 ps. Furthermore, we demonstrated that the ratio of energy transfer between the resonant energy states could be controlled.     

Na-Mg共掺杂ZnO薄膜的结构和光学性质

利用溶胶-凝胶法,在普通载玻片上使用旋转涂膜技术制备了具有c轴择优取向生长的Na-Mg共掺杂的ZnO薄膜。用XRD、SEM、光致发光(PL)及透射光谱对薄膜样品进行了表征。结果表明:Na-Mg共掺杂有利于ZnO薄膜的c轴择优取向生长,并且随着Na+掺杂浓度的增加,晶粒尺寸先增大后减小;通过比较不同掺杂浓度ZnO薄膜的PL谱,推测发光峰值位于380nm的紫外发射与ZnO的自由激子复合有关;发现掺入Mg的确能使ZnO禁带宽度增大,掺杂组分为Na0.04Mg0.2Zn0.76O时,其PL谱只有一个很强的紫光发射峰,其近带边紫外光发射强度较未掺杂的ZnO增强了近10倍,极大地提高了薄膜紫外发光性能;并且随Na+浓度增加薄膜透光性减弱。     

Strong exciton emission from ZnO microcrystal formed by continuous 532 nm laser irradiation

The Zinc oxide (ZnO) microcrystal is formed out of irradiated powder sample by a continuous-wave 532-nm laser with a high power of about 200 mW, and the microcrystal formation process is monitored by in situ Raman spectroscopy simultaneously. Scanning electron microscope image shows that multi-shaped ZnO microcrystal, including nano-rods and nano-flakes, is obtained near the brim of laser irradiated spot. The photoluminescence spectra of ZnO microcrystal are studied at both room temperature and low temperature of 10 K. With the ZnO microcrystal, we obtain that the peak intensity of near band-edge emission is at least 400 times stronger than that of deep-level emission at room temperature, and that up to fifth-order phonon replicas of free exciton emission are easily distinguished in the 10 K photoluminescence spectra. Both of them indicate that the ZnO microcrystal formed by intense laser irradiation has a very good crystalline structure.     

The photoluminescence characterization of the N-doped ZnO films produced by wet chemical deposition

The ZnO:N films are prepared by a wet chemical method. The temperature-dependent photoluminescence (PL) is used to investigate those ZnO: N films. Due to the introduction of nitrogen atoms into ZnO film, another phase appears in the ZnO film, which can release the stress and improve the film quality. As a result, a neutral donor-bound exciton (D⁰X) emission peak is shown in low temperature PL spectrum. With the increasing temperature, the D⁰X line gradually loses its intensity and shifts to 3.30 eV, which is consistent with the well-known conversion from bound exciton to free exciton at elevated temperatures. Then, due to the thermal quenching effect, the D⁰X line vanishes in room temperature. In addition, no shift is shown in the location of visible band emission and only the intensity decreases with the increasing temperature.