纳米ZnO薄膜的光致发光性质

利用溶胶－凝胶法制备了纳米ZnO薄膜,室温下测量了样品的光致发光谱(PL)、吸收谱(ABS)、X射线衍射谱(XRD)．X射线衍射(XRD)的结果表明：纳米ZnO薄膜呈多晶状态,具有六角纤锌矿晶体结构和良好的C轴取向．观察到二个荧光发射带,中心波长分别位于395 nm的紫带、524 nm的绿带和450 nm附近的蓝带．证实了纳米ZnO薄膜绿光可见发射带来自氧空位(VO)形成的浅施主能级和锌空位(VZn)形成的浅受主能级之间的复合;450 nm附近的蓝带来自电子从VO的浅施主能级到价带顶或锌填隙(Zni) 到价带顶或导带底到VZn的浅受主能级的复合．     

不同衬底上的ZnO薄膜紫外光致发光

用射频磁控溅射法在蓝宝石、硅和石英衬底上沉积出具有好的择优取向的多晶ZnO薄膜. 在270 nm波长的光激发下室温下可观察到显著的紫外光发射（波长为356 nm）和较弱的蓝光发射（波长为446 nm）. 经高温退火后薄膜的结晶质量显著提高, 在蓝宝石、石英衬底上沉积的薄膜，其积分发光强度分别增加了7倍和14倍.而硅衬底上的膜发光强度增强不太显著.紫外光发射源于电子的带间跃迁，而蓝光发射是由电子从氧空位浅施主能级到价带顶的跃迁引起的. 关键词： ZnO薄膜 射频磁控溅射 紫外发光 退火     

纳米ZnO薄膜可见发射机制研究

利用溶胶－凝胶法 （Sol-Gel）制备了纳米ZnO薄膜,获得了高强的近紫外发射室温下测量了样品的光致发光谱(PL )、吸收谱(ABS)、X射线衍射谱(XRD).X射线衍射(XRD)的结果表明：纳米ZnO薄膜呈多晶态,具有六角纤锌矿结构和良好的C轴取向;发现随退火温度升高,（002）衍射峰强度显著增强,衍射峰的半高宽（FWHM）减小、纳米颗粒的粒径增大.由吸收谱(ABS)给出了样品室温下带隙宽度为3.30 eV.在PL谱中观察到二个荧光发射带,一个是中心波长位于392 nm附近强而尖的紫带,另一个是519 nm附近弱而宽的绿带研究了不同退火温度样品的光致发光峰值强度的变化关系,发现随退火温度升高,紫带峰值强度增强、绿带峰值强度减弱,均近似呈线性变化.证实了纳米ZnO薄膜绿光发射主要来自氧空位(Vo)形成的浅施主能级与锌空位(VZn)形成的浅受主能级之间的复合,或氧空位(Vo)形成的深施主能级上的电子至价带顶的跃迁;紫带来自于导带中的电子与价带中的空位形成的激子复合.     

纳米晶ZnO可见发射机制的研究

利用化学沉淀法制备了纳米ZnO粉体,室温下测量了样品的光致发光谱(PL)、X射线衍射谱(XRD),给出了样品的透射电子显微照片(TEM).X射线衍射(XRD)的结果表明:纳米晶ZnO具有六角纤锌矿晶体结构,颗粒呈球形或椭球形.观察到二个荧光发射带,中心波长分别位于398 nm的紫带和510 nm的绿光带.发现随退火温度升高,粒径增大,紫带的峰值减弱、绿带的峰值增强.证实了纳米晶ZnO绿光可见发射带来自氧空位形成的施主和锌空位形成的受主之间的复合.     

掺Sb纳米ZnO的光致发光的研究

用柠檬酸盐法合成了不同掺杂浓度的纳米ZnO,粒径约为15nm。探讨了Sb掺杂对ZnO光致发光峰的影响。随着掺杂量的提高,样品的发射峰从428nm移至444nm。未掺杂ZnO的发光主要是源于电子从锌填隙形成的缺陷能级到价带顶的跃迁;随着掺杂量的提高,体系的氧空位增加,从而使得电子从氧空位所形成的缺陷能级到价带顶的跃迁占据主导,光致发射峰向长波方向移动。     

氧氩比对纳米ZnO薄膜蓝光发射光谱的影响

利用射频磁控溅射方法,在石英表面上制备了具有良好的c轴取向的纳米ZnO薄膜。室温下,在300 nm激发下,在450 nm附近观测到ZnO薄膜的蓝光发射谱(430~460 nm)。分析了气氛中氧气与氩气比对薄膜质量及蓝光发射光谱的影响,给出了纳米ZnO薄膜光致发光谱(PL)的积分强度和峰值强度与氧氩比关系。探讨了纳米ZnO薄膜的蓝光光谱的发射机制,初步证实了ZnO蓝光发射(2.88~2.69 eV)来自氧空位(VO)形成的浅施主能级上的电子至价带顶的跃迁。     

纳米ZnO镶嵌SiO2薄膜的磁控溅射制备和发光性质的研究

采用射频磁控反应溅射方法在SiO衬底上制备了纳米ZnO镶嵌SiO2薄膜.在室温下利用吸收光谱和光致发光光谱研究了样品的光学性质.发现吸收光谱随纳米ZnO尺寸的减小发生了明显的蓝移,表明随着ZnO尺寸的减小,量子尺寸效应增强,导致带隙展宽,吸收峰蓝移.光致发光光谱在387和441 nm附近出现了两个发光带,分析认为紫外发光来源于自由激子的辐射复合,而蓝色发光带来自于氧空位的电子到价带的跃迁,并用时间分辨光谱和发光衰减证实了上述观点.     

激光分子束外延方法生长的ZnO薄膜的发光特性

研究了不同温度和不同光激发强度下激光分子束外延方法生长的ZnO薄膜样品的发光性能,发现YAG脉冲激光激发,强度超过一定值时会在长波方向上出现一个新的发光峰,此峰可能起源于电子-空穴的复合。室温下氙灯激发的光谱中可以看到峰值位于381nm的近带边紫外发射峰和位于450nm的强的蓝绿带发射,根据光致发光激发光谱的特征给出了一个简单的蓝光发射模型。对比YAG脉冲激光激发和氙灯激发得到的实验光谱,我们认为不同的光谱特征和样品发光的激发机制有关,紫外峰发射需激发强度超过一定值才能观察到,而蓝带发射则在一定的激发强度下迅速饱和。     

A面(11-20)ZnO薄膜中杂质的偏振PL谱研究

本文通过分析A面(11-20)ZnO薄膜的低温PL(光致发光)光谱偏振特性来研究ZnO光致发光谱中杂质峰的来源。低温(4 K)下观察到476、479 nm两处新的杂质峰以及390 nm处激子峰,根据两个杂质峰的偏振特性,初步判定476nm峰来源于氧空位能级到价带轻空穴的跃迁,479 nm峰来源于氧空位价带重空穴的跃迁。     

ZnO纳米线双绝缘层结构电致发光器件制备及特性研究

在利用液相法生长ZnO纳米线薄膜的基础上，构造成功基于ZnO纳米线双绝缘层结构的交流电致发光器件.此器件呈现出良好的阻容特性，在室温下以一定频率的交流电压驱动，可观察到近紫外波段387 nm处和可见光波段552 nm处的发射谱带.从阻容结构的导电特性及ZnO纳米线材料的能带结构等方面探讨了这种器件的电致发光机理及频率特性.     

Enhanced electroluminescence of ZnO nanocrystalline annealing from mesoporous precursors

An improved sol-gel method was used to prepare ZnO nanoparticles. EL results showed that slowing the addition of LiOH solution and heating in vacuum to obtain gel precipitation made the final ZnO samples’ emission peak blue shift to 520 nm. Simultaneously, the peak value of the sample processed with no templates was enhanced 4.68 times and that of the sample processed with ODA was enhanced 0.71 times. Two copolymers Pluronic P123 (P123) and Pluronic F-127 (F-127) were adopted respectively as template reagents. The obtained mesoporous ZnO precursors exhibited a surface area of 69.21 m²/g and 103.57 m²/g and an average pore size of 6.61 nm and 5.70 nm, respectively. After calcining in a muffle furnace in air, the obtained ZnO nanocrystalline samples from these precursors revealed stronger green emission than the samples dealt with ODA. Compared to the magnification multiple of 0.89 times of the sample processed with ODA, the peak intensity of the sample processed with P123 was 2.03 times higher than that of the sample processed with no template reagents, and the intensity of the sample processed with F-127 was 3.3 times higher. This may be due to the larger surface area of samples from the longer molecule chains of the two template reagents.     

ZnO薄膜表面和边缘的发光特性

研究了分子束外延方法生长的ZnO薄膜的光学特性,首先测量样品反射光谱,然后重点研究其光致发光光谱。实验中通过改变激发光的强度,以及采用波导配置和不同的实验几何配置等手段,观察到了ZnO薄膜中起源于激子-激子散射和电子-空穴等离子体复合发光的受激辐射,同时观察到两种配置下自发辐射谱中存在巨大的差异。通过对实验数据和理论计算结果的分析,初步认为造成了从ZnO薄膜表面和侧面得到的PL谱之间的显著区别原因有两种:一是非对称薄膜波导的吸收损耗造成的波长选择效应,二是薄膜波导对掠出射光的类似薄膜微腔的微腔效应。     

Influence of annealing on the scintillation properties of zinc oxide powders and ceramics

It was shown that annealing ZnO and ZnO:Ga initial powders and ceramics in different atmospheres significantly changes the characteristics of the studied samples. Two main luminescence bands of different origins were observed in powders at 540 nm and 580 nm. Annealing either in vacuum or in Ar:H₂ atmosphere increased intensity of green luminescence with peak at 540 nm whereas annealing in air enhanced a luminescence band with peak at 580 nm in the powders. Corresponding changes in luminescence kinetic properties were observed. Annealing of the ceramics in vacuum and air did not affect the luminescence properties, while annealing them in Ar:H₂ atmosphere increased green luminescence intensity of undoped ceramics and excitonic luminescence intensity of doped ones. Comparison of the X-ray, gamma-ray and cathode-ray excited luminescence lead to conclusion that the enhancement of luminescence intensity took place in surface layer of about 100 μm thickness.     

ZnMgO/n-ZnO/ZnMgO/p-GaN异质结LED的紫外电致发光

利用等离子体辅助分子束外延( P-MBE)技术制备了ZnMgO/n-ZnO/ZnMgO/p-GaN异质结LED.Ni/Au电极与p-GaN、In电极与ZnMgO之间都形成了良好的欧姆接触.在ZnMgO/n-ZnO/ZnMgO/p-GaN异质结器件中观察到了明显的整流特性.异质结的电致发光强度随着注入电流的增大而逐渐增强...     

氧化锌纳米粉体的制备及其光催化性能研究

采用溶胶-凝胶法制备了氧化锌光催化剂,分别利用XRD、TG、FT-IR对所制粉体进行了表征。结果表明ZnO为六方晶系纤锌矿型,粒子大小约为27nm。粉体的IR光谱表明,热处理后NH基团和单乙酸锌的吸收峰消失,在470cm-1附近出现Zn-O伸缩振动。纳米粉体的光催化降解水杨酸实验结果显示出,焙烧后所得的纤锌矿型ZnO粉体具有较高的光催化活性,以310nm波长光照射16小时可降解水杨酸95.1%。     

van der Waals gap-inserted light-emitting p–n heterojunction of ZnO nanorods/graphene/p-GaN film

We report on the electroluminescent (EL) and electrical characteristics of graphene-inserted ZnO nanorods (NRs)/p-GaN heterojunction diode. In a comparative study, ZnO NRs/p-GaN and ZnO NRs/graphene/p-GaN heterojunctions exhibit white and yellow EL emissions, respectively, at reverse bias (rb) voltages. The different EL colors are results of different dichromatic EL peak intensity ratios between 2.25 and 2.8 eV light emissions which are originated from ZnO and p-GaN sides, respectively. The 2.25 eV EL is predominant in both the heterojunctions, because of recombination by numerous electrons tunneled from p-GaN to ZnO across the thin barriers of the staggered broken gap with a large band offset in ZnO/p-GaN and the van der Waals (vdW) gap formed by graphene insertion at ZnO NRs/p-GaN. However, as for the 2.8 eV EL intensity, ZnO NRs/graphene/p-GaN hardly shows the EL emission, whereas ZnO NRs/p-GaN exhibits the substantially strong EL peak. We discuss that the significantly reduced 2.8 eV EL emission of ZnO NRs/graphene/p-GaN is a result of decreased depletion layer thickness at p-GaN side where the recombination events occur for 2.8 eV EL before the reverse bias-driven tunneling because the insertion of graphene (or vdW gap barrier) inhibits the carrier diffusion whose amount determines the depletion thickness when forming the heterojunctions. This study opens a way of suppressing (or enhancing) the specific EL wavelength for the dichromatic EL-emitting heterojunctions simply by inserting atom-thick vdW layer.     

Enhanced electroluminescence from ZnO‐based heterojunction light‐emitting diodes by hydrogen plasma treatment

The effects of H‐plasma treatment on the electroluminescence (EL) of ZnO‐based light‐emitting diodes have been investigated systematically. After H‐plasma treatment, the EL intensity of the n‐ZnO/AlN/p‐GaN device is observed to be three times stronger than its as‐grown counterpart under the same injection current, and the threshold voltage of the device is significantly reduced simultaneously. The increases in electron concentration and mobility of the ZnO layer resulting from the incorporation of hydrogen atoms into ZnO are considered to be responsible for the improved performance of the ZnO‐based light‐emitting diodes. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

超声处理对ZnO薄膜光致发光特性的影响

对于结晶状态好的ZnO薄膜，测量了其光致发光(PL)光谱，发射光谱中只发现了峰值波长约389 nm的近紫外光.样品进行超声处理后，发射谱中不仅观察到近紫外峰，又观察到波长约508 nm的绿光峰.绿光峰的强度比近紫外光的强度强得多，且近紫外峰红移.进一步的热处理使绿光峰大大增强.超声处理改变了ZnO薄膜的质量和结晶状态，使晶格中产生氧空位.处理过程中的热效应使得薄膜晶格振动加剧.当晶格振动加剧到一定程度，晶格中的氧脱离格点形成氧空位.510 nm左右的绿色发光峰是ZnO晶体中的氧空位产生的.薄膜的温度越高， 关键词： ZnO薄膜 超声 光致发光     

有机层厚度变化的有机电致发光器件与微腔器件光谱分析

设计中心波长为520nm,改变有机层厚度,即空穴传输层NPB和发光层Alq3的厚度,分别由10nm逐渐增加至100nm,器件的总体厚度也随着改变,分别计算模拟出有机电致发光器件(OLED)和微腔有机电致发光器件(MOLED)的电致发光谱(EL),并对光谱的积分强度、峰值强度、半峰全宽、峰值位置的三维分布图进行比较分析。综合考虑光谱的峰值位置(中心波长)、最大的峰值强度和积分强度(与亮度、效率相关)、最小半峰全宽(色纯度高)进行合理的设计,可以找到最佳厚度。发现:NPB和Alq3的厚度分别为70和62nm时,器件性能最佳,并且微腔器件的结果尤为明显。结果表明,通过模拟计算,可以深入探索MOLED和OLED发光特性,设计出合理的器件结构。     

ZnO：V薄膜后退火处理前后的微结构与发光特性

利用溶胶-凝胶(Sol-gel)法在单晶硅(100)衬底上分别制备了ZnO:V薄膜和纯ZnO薄膜。为进一步研究后退火对ZnO:V薄膜结构和发光性质的影响,在两段式快速退火后又在800℃下进行了后退火处理。X射线衍射的结果表明:后退火处理前,钒(V)的掺入使ZnO结晶质量变差,而800℃退火处理后,从ZnO的衍射峰中可以看出,相对于无V杂样品其结晶质量变好。扫描电子显微镜形貌图中可以看出制备的样品薄膜颗粒大小均匀,薄膜致密度较高。光致发光(PL)谱的研究表明:ZnO:V薄膜在800℃退火处理后,紫外和绿带发光峰均增强,但紫外发光峰增强得更多;与同样条件下制备的纯ZnO薄膜的PL谱比较,发现V掺杂后样品的紫外激子复合发光峰的强度明显增强且峰位发生蓝移,而缺陷引起的绿带发光峰的强度降低。