Mg/Cd共掺杂ZnO电子结构与光学性质的第一性原理研究

采用基于密度泛函理论的第一性原理平面波超软赝势法,研究了Mg/Cd(不同的Cd浓度)共掺杂ZnO的电子结构和光学性质.研究表明:Mg/Cd共掺杂ZnO,体系的晶胞尺寸变大,但结构稳定.当Mg/Cd为1:1时,吸收边略微发生蓝移.随Cd的掺杂浓度增加,导带部分逐渐下移,禁带宽度变窄,出现红移现象.除此之外体系的吸收率和反射率也减小.说明Mg/Cd共掺杂ZnO,不仅使得体系光学谱丰富,而且透射性增强.这对实验中制备出高透射率的材料具有一定的指导意义.     

第一性原理研究Cd掺杂对ZnO电子结构与光学性质的影响

采用第一性原理平面波超软赝势方法超软赝势方法,研究了Cd掺杂前后ZnO的电子结构以及光学性质.计算结果发现:Cd的掺入使得ZnO的电子结构发生了改变,晶胞变大,禁带宽度变窄.Cd掺杂使ZnO的光学性质也发生了变化,4.3 eV处的介电峰增强并发生红移,12.9 eV处的介电峰减弱,对紫外光吸收作用增强.     

溶胶-凝胶法制备Mg掺杂ZnO薄膜的微结构与光学性质

采用溶胶-凝胶技术在Si(111)和石英玻璃衬底上制备了Mg掺杂ZnO薄膜.用X射线衍射仪(XRD)、原子力显微镜(AFM)、扫描电镜(SEM)和紫外-可见(UV-Vis)分光光度计测试薄膜的微结构、表面形貌和光学性质.结果表明:所得Mg掺杂ZnO薄膜仍为六角纤锌矿型结构,呈c轴方向择优生长,随着退火温度升高,薄膜的晶格常数c由0.5288 nm减小到0.5278 nm,粗糙度从3.8 nm增大到6.5 nm,光学带隙由3.26 eV增大到3.31 eV.     

Ag,O共掺实现p型氮化铝纳米管电子结构的第一性原理研究

基于第一性原理的平面波超软赝势法对(6, 0)单壁氮化铝纳米管、Ag掺杂,以及Ag和O共掺纳米管进行了几何结构优化。计算讨论了掺杂前后氮化铝纳米管的能带结构、态密度和差分电荷密度。研究显示:本征氮化铝纳米管、Ag掺杂和Ag-O共掺氮化铝纳米管的带隙分别为2.49 eV、1.84 eV和1.80 eV。掺杂构型仍然保持半导体特性,Ag掺杂氮化铝纳米管的价带顶贯穿费米能级从而形成简并态,实现了氮化铝纳米管的p型掺杂,但Ag-4d态和N-2p态电子轨道间有强烈的杂化效应,Ag的单掺总体上是不稳定的。O掺入后,Ag与O之间的吸引作用克服了Ag原子之间的排斥作用,使Ag在氮化铝纳米管中的掺杂更加稳定;共掺纳米管体系的带隙相较于单掺纳米管体系更加窄化,导电性进一步增强。Ag和O共掺有望成为获得p型氮化铝纳米管的有效方法。     

Eu、Mg共掺ZnO薄膜的微观结构与光致发光性能研究

采用射频磁控溅射技术,以不同Eu、Mg掺杂比的ZnO/MgO/Eu2O3陶瓷靶材,制备了Eu、Mg共掺的ZnO薄膜(ZMEO).通过X射线衍射(XRD)、Raman散射及光致发光(PL)技术研究了Eu、Mg掺杂比对ZMEO薄膜微观结构和光致发光性能的影响.结果表明:所制备的ZMEO薄膜皆为六角纤锌矿型结构.适当的Eu、Mg掺杂比不但有利于ZnO晶粒的生长,而且可以引入缺陷俘获导带电子,促进ZnO和Eu3+之间的能量传递,使Eu3+的红光发射强度获得提升.     

掺Cd对ZnO薄膜光学性能的影响

采用溶胶-凝胶法在石英玻璃上制备了不同掺Cd浓度的ZnO薄膜.X射线衍射(XRD)结果表明,所制备的薄膜具有c抽择优取向,随着Cd掺杂浓度的升高,(002)峰向低角度方向移动.UV透射曲线表明,薄膜具有明显的紫外吸收边,通过改变Cd的掺入浓度,可以使吸收边向长波方向移动并被控制在一定范围内,从而使薄膜的禁带宽度连续可调;薄膜的光致发光(PL)谱显示,ZnO薄膜的PL谱是由紫外激子发光峰和蓝光发光带组成,通过掺入Cd可使紫外带边发射的峰位向低能端方向红移,这与透射谱中吸收带边的红移相吻合,由紫外发光峰得到的光禁带宽度和由透射谱拟合得到的光禁带基本一致.对不同掺杂浓度的薄膜进行了比较,发现Cd掺入量为8;摩尔分数时ZnO薄膜具有最佳的结构性能和发光性能.     

不同浓度Nb掺杂ZnO第一性原理研究

本文采用基于密度泛函理论的第一性原理计算了不同浓度Nb掺杂ZnO的能带结构及性能,并对本征ZnO、Al掺杂ZnO(AZO)和Nb掺杂ZnO(NZO)的模拟结果进行对比分析。结果表明:(1)NZO和AZO的带隙值均低于本征ZnO的带隙值,掺杂浓度(原子数分数)同为6.25%的NZO的带隙值低于AZO的带隙值。随着Nb掺杂浓度增高,NZO的导带底明显降低,态密度峰值降低,且Nb-4d态电子占据了费米能级的主要量子态。(2)随着掺杂浓度的增加,NZO和AZO吸收峰和介电函数峰均降低,且向低能区移动,其中,NZO吸收峰向低能区移动更明显,且介电函数虚部分别在0.42 eV和34.29 eV出现新的峰,主要是价带中Nb-4d和Nb-5p电子能级跃迁所致。掺杂浓度同为6.25%的NZO的静介电常数大于AZO的静介电常数,表明NZO极化能力更强,NZO可以更有效改善ZnO的光电性能。随着Nb掺杂浓度增加,NZO的吸收系数和介电函数虚部强度增加且向高能区移动。NZO的模拟结果为高价态元素Nb掺杂ZnO的实验研究工作及实际应用提供了理论参考。     

Li-N共掺ZnO纳米管的第一性原理研究

采用基于密度泛函理论的计算方法,系列的研究了锯齿型(9,0) ZnO单壁纳米管、Li,N分别掺杂以及Li-2N共掺杂的ZnO纳米管的能带结构、总体态密度、分波态密度.分析发现虽然Li原子单独掺杂不会对纳米管能带结构产生明显影响,但是Li-2N共掺杂比N单独掺杂ZnO纳米管的结构更加稳定,而且Li-2N共掺杂ZnO纳米管是p型简并半导体.     

衬底温度对磁控溅射法制备掺Ta氧化锌薄膜性能的影响

采用射频磁控溅射法,在不同的衬底温度下制备了钽(Ta)掺杂的氧化锌(ZnO)薄膜,采用X射线能谱(EDS)、X射线衍射(XRD)、扫描电镜(SEM)、紫外-可见分光光度计和光致发光(PL)光谱研究了衬底温度对制备的Ta掺杂ZnO薄膜的组分、微观结构、形貌和光学特性的影响.EDS的检测结果表明,Ta元素成功掺入到了ZnO薄膜;XRD图谱表明,掺入的Ta杂质是替代式杂质,没有破坏ZnO的六方晶格结构,随着衬底温度的升高,(002)衍射峰的强度先增大后降低,在400℃时达到最大;SEM测试表明当衬底温度较高时(400℃和500℃),Ta掺杂ZnO薄膜的晶粒明显变大;紫外-可见透过光谱显示,在可见光范围,Ta掺杂ZnO薄膜的平均透光率均高于80;,衬底不加热时制备的Ta掺杂ZnO的透光率最高;制备的Ta掺杂ZnO薄膜的禁带宽度范围为3.34~3.37eV,衬底温度为500℃时制备的Ta掺杂ZnO薄膜的禁带宽度最小,为3.34eV.PL光谱表明衬底温度为500℃时制备的Ta掺杂ZnO薄膜中缺陷较多,这也是造成薄膜禁带宽度变小的原因.     

Mg掺杂对CaMnO3基热电氧化物电子结构及电性能的影响研究

采用超软赝势密度泛函理论计算的方法研究了Mg掺杂Ca位CaMnO3基复合氧化物的能带结构、电子态密度和电荷分布状况,在此基础上分析了Mg掺杂氧化物的电性能.结果表明,Mg掺杂CaMnO3氧化物仍然呈间接带隙型能带结构,带隙宽度由0.756eV减小到0.734eV.CaMnO3氧化物和Mg掺杂CaMnO3氧化物的自旋态密度曲线极值点均位于为-0.8eV附近.Mg掺杂CaMnO3氧化物中Mn原子对体系费米面态密度的贡献有所减小,O原子和Ca原子对体系费米面态密度的贡献有所增大.Mg原子比Ca原子具有更强的释放电子的能力,Mg掺杂对于CaMnO3氧化物属于电子型掺杂.Mg掺杂CaMnO3氧化物导电性能增强,电性能提高.     

衬底温度对Cu2O薄膜结构和性能的影响

采用射频磁控溅射技术在石英衬底上制备了Cu2O薄膜。系统研究了衬底温度对薄膜结构、光学和电学性能的影响。XRD的结果显示,在所有衬底温度条件下均可得到单相的Cu2O结构,而且随着衬底温度由500 K升至800 K,薄膜表现出(111)择优取向的生长特点。电学和光学测试结果表明,室温电导率和光学带隙随着衬底温度的升高而增加,800 K制备的薄膜的带隙值最高约为2.58 eV。     

Optical properties of ZnO nanotubes

Tubular ZnO nanostructures have been obtained via a hydrothermal method at low temperature (90 °C) without any catalysts or templates. The XRD measurement reveals that the tubes are single crystals with hexagonal wurtzite structure. SEM shows that the diameters of ZnO nanotubes ranged from 400 to 550 nm. The Raman and PL spectra indicate that oxygen vacancies or Zn interstitials are responsible for the green emission in the ZnO nanotubes. A possible growth mechanism on the formation of crystalline ZnO nanotubes has been presented. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Solution-processible Cd-doped ZnO nanoparticles as an electron transport layer to achieve high performance polymer solar cells through improve conductivity and light transmittance

Abstract

In this work, electron transport layers (ETLs) with high charge transfer ability were prepared by doping ZnO nanoparticles with different concentrations of cadmium(Cd). The inverted polymer solar cell based on PTB7-Th: PC₇₁BM as active layer and various concentrations Cd-doped ZnO (CZO) as ETLs were fabricated. The PCE of the device with optimized Cd content in the ZnO film was about 14.7% larger than that of the pure ZnO-based cells. The cadmium-doped ZnO(CZO) is a good candidate to be used as a high-quality transparent electrode in solar cell applications.     

Structural,Raman, and photoluminescence properties of double‐shelled coaxial nanocables of In2O3 core with ZnO and AZO shells

We synthesized In₂O₃/ZnO/Al‐doped ZnO (AZO) core‐double shell nanowires, in which the inner shell (ZnO) and the outer shell (AZO) have been subsequently deposited on the core In₂O₃ nanowires. With their one‐dimensional morphology being preserved, the X‐ray diffraction (XRD), lattice‐resolved transmission electron microscopy (TEM) image, selected area electron diffraction, and Raman spectrum coincidentally revealed that the shell was comprised of hexagonal ZnO phase. In addition, TEM‐EDX investigation revealed the presence of Al elements in the shell region. The thermal annealing at 700 °C did not significantly change the nanowire morphology, however, the XRD spectrum indicated that the ZnO phase was crystallized by the annealing. PL spectrum of the 700 °C‐annealed In₂O₃/ZnO/AZO core‐double shell nanowires was comprised of three Gaussian bands at approximately 2.1 eV, 2.4 eV, and 3.0 eV, respectively. The integrated intensities of 2.1 eV‐, 2.4 eV‐, and 3.0 eV‐bands were decreased by the thermal annealing. This study will pave the road to the preparation and applicaition of double‐shelled nanowires. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

不同形貌的纳米氧化锌粉的光学性能研究

本文采用水热和溶剂热法制备了粒状、棒状、片状、管状纳米氧化锌粉体,并对四种不同形貌的氧化锌粉的光学性能进行了对比研究.结果表明:氧化锌纳米粒,纳米片和纳米管在200~400 nm区域的反射率均低于8;,而氧化锌纳米棒在200~400 nm区域的反射率大约为18;.氧化锌纳米管对甲基橙的光催化降解效果最好,在距离30 cm 的30 W紫外灯条件下进行照射,8 h完全降解,而氧化锌纳米棒对甲基橙的光催化降解效果最差,在相同的实验条件下,氧化锌纳米棒的降解率仅为70;.     

CuInS2量子点敏化ZnO基光阳极的制备与性能研究

采用两步法在导电玻璃(FTO)基板上制备纯氧化锌(ZnO)纳米棒和钇掺杂的氧化锌(ZnO∶Y)纳米棒,采用连续离子层吸附反应法(SILAR)在所制备的ZnO及ZnO∶Y纳米棒上沉积CuInS₂量子点制备ZnO/CuInS₂和ZnO∶Y/CuInS₂光阳极。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、电子探针能谱仪(EDS)、紫外-可见分光光度计(UV-Vis)、电流密度-电压(J-V)曲线等技术手段对不同光阳极样品的晶相结构、微观形貌、化学组成、光吸收性能和太阳电池性能进行了表征。实验结果表明:所制备的ZnO纳米棒和ZnO∶Y纳米棒为六方纤锌矿结构。CuInS₂量子点敏化的ZnO纳米棒薄膜的光学带隙从3.22 eV减小为2.98 eV。CuInS₂量子点敏化ZnO∶Y太阳能电池的短路电流密度和光电转换效率比未掺杂的ZnO纳米棒组装的太阳能电池分别提高了6.5%和50.4%。     

Self-sacrificed template method for the synthesis of ZnO-tubular nanostructures:reaction kinetics and pathways

Using Zn nanowires as a self-sacrificed template, hierarchical tubes constructed by zinc oxide (ZnO) nanoflakes and ZnO nanotubes have been successfully fabricated by two different thermal-oxidation modes. The products were characterized by the X-ray powder diffraction, transmission electron microscopy and field-emission scanning electron microscopy. The experimental results show that the formation processes of ZnO nanostructures are sensitive to the growth temperature, which is lower or higher the melting point of Zn (419 °C). ZnO nanoflake tubes and ZnO nanotubes can be controlled through the variation of the heat-treatment process of Zn nanowires and their growth pathway can be described by two types of growth mechanism, in terms of Kirkendall effect and the sublimation of the Zn cores, respectively. Our method provides an easy and convenient way to prepare metal oxides tubular nanostructures with different morphologies through self-sacrificed template method via adjusting the heat-treatment process.     

Zinc oxide – analogue of GaN with new perspective possibilities

Zinc oxide due to specific electrical, optical and acoustic properties is the important semiconductor material, which has many various applications. There is growing interest in ZnO due to its potential applicability for optoelectronic devices such as light‐emitting diodes, laser diodes and detectors for UV wavelength range. ZnO properties are very close to those of widely recognized semiconductor GaN. The band gap of ZnO (3.37 eV) is close to that of GaN (3.39 eV) but ZnO exciton binding energy (60 meV) is twice larger than that of GaN (28 meV). Optically pumped UV lasing have been demonstrated at room temperature using high textured ZnO films. The excitonic gain close to 300 cm^–1 was achieved. ZnO thin films are expected to have higher quantum efficiency in UV semiconductor laser than GaN. The physical properties of ZnO are considered. PEMOCVD technology was used to deposit piezoelectric and highly transparent electroconductive ZnO films. Their properties are discussed. The experiments on polycrystalline ZnO films deposited by RF magnetron sputtering at different partial pressure of oxygen are presented. AFM images were studied in tapping mode for deposited films. The investigated films were dielectric ones and had optical transparency within 65‐85% at thickness in the interval 0.2‐0.6 μm. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)