ZnO纳米带梳的制备及生长机理的研究

采用化学气相沉积(CVD)法成功制备出ZnO纳米带梳,实验过程不需要催化剂.X射线衍射仪(XRD)分析结果表明,ZnO纳米带梳为高度结晶的六方纤锌矿结构;利用扫描电子显微镜(SEM)观测,所制样品是由纳米带组成梳状形貌,纳米带梳的形成经过两个步骤:先通过VS机制形成微米带,而梳的齿通过自催化生长平行于(0001)极性面形成.对样品的光致荧光(PL)谱测量发现了位于～395nm和495nm处的室温光致发光峰.     

水热法可控合成ZnO微纳米结构及其光致发光性能研究

以锌金属片作为源物,卤族元素的碱金属盐溶液作为添加剂,采用水热法合成了氧化锌(ZnO)的管簇状、片簇状、棱柱状和多足状等微纳米结构.采用扫描电子显微镜(SEM),X射线衍射(XRD)表征了其形貌及晶体结构.详细研究了不同卤族元素离子对氧化锌形貌的影响,并研究了其生长机理.利用荧光光谱仪测试了不同形貌ZnO微纳米结构的光...     

以石墨为助剂反应合成ZnO晶体

用微米ZnO粉为原料,添加适量石墨助剂,采用高温热蒸发法合成ZnO纳米晶体材料,研究了不同温度对反应合成ZnO晶体形貌的影响,用XRD、SEM和EDS分析了产物的物相组成与显微形貌。研究结果表明,1000℃时可形成锯片状ZnO晶体,锯齿状晶粒长约100~200μm,宽度约4μm左右。锯齿的直径约0.3μm,长度约3~4μm。此外还有一些ZnO晶体呈六棱柱状生长,长约6~10μm,边长约1μm。1100℃时形成了大量ZnO棱柱晶粒,长约几百μm,比较粗大的晶粒达1mm。粗大的ZnO晶粒上生长着许多细小的ZnO四脚晶粒,长度约4~6μm,边长约1~2μm。     

低温水热法生长ZnO纳米棒阵列的电子结构及光学特性(英文)

使用低温水热法在Si衬底上生长ZnO纳米棒阵列.通过X射线衍射和扫描电子显微镜对ZnO纳米棒的结晶性和形貌进行观测.结果表明,六棱柱形ZnO纳米棒沿c轴方向的阵列性良好,且均匀致密的生长在衬底上.室温光致发光谱表明应用低温水热法可以得到光学性质良好的ZnO纳米棒阵列.使用同步辐射对ZnO纳米棒阵列的氧K带边进行X射线吸收近带边谱测量,研究了不同半径ZnO纳米棒阵列的局部电子结构及其半径对电子结构的影响.另外,对ZnO纳米棒及ZnO薄膜的局部电子结构进行了对比研究.     

梳状氧化锌纳米材料的制备及结构、性能的表征

通过纯锌粉蒸发，在600-650℃无催化条件下成功制备了高质量的梳状ZnO纳米结构。通过扫描电镜（SEM）及高分辨透射电镜（HRTEM）观察，所制备的梳状ZnO纳米结构具有两种典型形貌，且皆为单晶结构，分析表明其生长由气-固生长机理控制。室温光致发光谱显示，梳状ZnO纳米结构在385nm附近形成紫外发射峰；在以495nm为中心的范围内，形成较宽的绿光发射峰。     

蒲公英状ZnO微米球的控制组装与表征

本文用热蒸发气相沉积的方法在镀有金催化剂的锌片上成功合成了蒲公英状ZnO微米球结构。扫描电镜观察结果表明合成的ZnO微米球平均直径约5微米,表面二次生长的纳米线平均直径约20纳米,长度达几微米。透射电镜分析发现二次生长的纳米线具有单晶结构,其生长方向沿[001]方向。同时研究了沉积衬底、原材料种类和比例对合成产物形貌的影响,对合成微米球的室温光致发光性能进行了研究。合成的这种微米球结构在传感器等纳米器件领域有着潜在的应用前景。     

具有四角状棒-线结构纳米氧化锌的制备和性能

用气相氧化法合成出具有纳米棒-线结构的ZnO纳米材料.扫描电子显微镜(SEM)、透射电子显微镜(TEM)观察和X射线衍射谱(XRD)的分析表明:四角状ZnO纳米材料具有六方纤锌矿晶体结构,在棒-线纳米结构中,每个角的长度为1～2 μm,纳米棒的直径为100～200 nm,纳米线的直径约为30 nm.用气-固(VS)生长机制解释了棒-线纳米结构的形成.与ZnO大块材料不同,四角状ZnO纳米棒-纳米线材料在室温下具有～380 nm波长的紫外发射和～520 nm波长的绿光发射,其机理是晶体中杂质与结构缺陷少,以及与其纳米尺度相联系的量子限域效应.     

纳米氧化锌的制备及其光致发光性能研究

采用低温蒸发和气相输运方法,研制出ZnO的纳米棒－纳米钉、纳米钉类球状聚集体和具有钉状结构的纳米梳。利用透射电子显微镜和X射线衍射仪对其形貌与结构进行了表征,阐明了ZnO纳米结构的生长机理。用荧光光谱仪测量了退火前后纳米棒－纳米钉结构的光致发光谱,结果显示,在380nm处两者均存在近紫外峰,在500nm处出现绿色宽谱峰,而退火2h后近紫外发光峰窄而强,且发生了少许蓝移,此现象可归因于退火后的ZnO纳米结构具有较低的点缺陷浓度。     

一种P掺杂ZnO纳米梳的制备及其光致发光性能研究

采用化学气相沉积(CVD)方法制备了P掺杂ZnO纳米梳,扫描电子显微镜(SEM)结果显示,纳米梳状产物均匀分布在Si衬底上。P掺杂ZnO纳米梳为高度结晶的六方纤锌矿结构,ZnO中P的掺杂含量约为2%(原子分数)。室温光致发光(PL)光谱表明,P掺杂ZnO纳米梳在样品不同区域的发光性能略有不同,但是均出现3个发光峰:紫外、绿光和近红外发光峰。同时PL结果也表明样品的整体结晶质量比较好。     

不同形貌氧化锌的乙醇胺辅助水热制备及光催化性能

采用乙醇胺辅助水热的方法制备了一系列不同形貌的具有高效光催化性能的氧化锌纳米/微米晶。通过简单地调控乙醇胺的加入量得到了六方棱柱状孪晶、六方棒和三维花状等形貌。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、紫外-可见(UV-Vis)分光光谱等对样品进行了表征。在模拟太阳光氙灯的照射下,研究了不同形貌氧化锌光降解甲基橙的性能,发现六方棱柱状孪晶氧化锌表现出最佳的光催化活性。     

Dendritic and epitaxial growths of ZnO particle-rod and rod-rod nanostructures with quasi-one-dimensional and two-dimensional configurations

Quasi-one-dimensional and two-dimensional ZnO nanostructures have been fabricated through thermal evaporation approach. The microstructures of the ZnO nanostructures have been studied using scanning electron microscopy and high-resolution electron microscopy. Quasi-one-dimensional ZnO nanostructures are formed by dendritic growths of ZnO nanoparticles from the stem nanorods surfaces, forming particle-rod nanostructures. While epitaxial growths of branch nanorods from the stem nanorods configure two-dimensional ZnO nanostructures. The epitaxial growth orientation relationship can be described as [2? 110]_R1 || [2? 110]_R2 and (0001) _R1 || (011?0)_R2. The growth mechanism of the quasi-one-dimensional and two-dimensional ZnO nanostructures has been discussed.     

Structure analyses and growth mechanism of ZnO nanoladders

Novel ZnO nanoladders have been synthesized by a simple chemical vapor deposition. Transmission electron microscopy and high-resolution transmission electron microscopy investigations reveal that one ZnO nanoladder consists of two nanobelts whose growth directions are different to each other. The grain boundary in the middle of the junctions between the two nanobelts is clearly observed. A two-step growth model is speculated to interpret the growth of ZnO nanoladder based on the detailed structure analyses. The super-saturation of the Zn vapor and the Coulomb repulsion between the two nanobelts are the dominating factors for the growth of ZnO nanoladders.     

Temperature-dependent controlled preparation of ZnO nanostructures and their photoluminescence properties

High purity and yield of ZnO nanobelts, nanocombs and nanowires have been synthesized using a simple catalyst-free vapor transport process and their growth mechanism and photoluminescence properties have been investigated. Transmission electron microscopy and selected-area electron diffraction analyses reveal that the intrinsic growth behaviors of ZnO vary with the growth temperature, leading to the formation of nanostructures with different morphologies. These ZnO nanostructures show a UV emission at about 385 nm and a broad green emission around 500 nm in their photoluminescence spectra, and the green to UV emission intensity ratio is determined by their microstructures.     

Morphological control of flower-like ZnO nanostructures

Flower-like ZnO nanostructures composed of different building blocks, such as hexagonal pyramids, hexagonal prisms, and cones, have been synthesized on a large scale by a simple hydrothermal method in the absence of surfactants or organic solvents. The effects of the concentration of NaOH, reaction temperature, and reaction time on the morphologies of the resulting products have been investigated. The morphologies and the crystal structures of flower-like ZnO nanostructures were characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM).     

Epitaxial growth of nonpolar m-plane ZnO (10-10) on large-size LiGaO2 (100) substrates

Nonpolar m-plane ZnO epitaxial film with [10-10] orientation was successfully grown on a large-size (100) LiGaO₂ single crystal substrate by chemical vapor deposition method. The dependence of growth characteristics on the different growth conditions was investigated. Following CVD growth, the surface morphologies and epi-film crystallinity were examined by scanning electron microscopy and X-ray diffraction. Room-temperature photoluminescence spectra exhibit a strong near-band-edge emission peak at 377 nm with a negligible green band. Raman spectroscopy showed that the as-grown (10-10) ZnO epilayer on (100) LiGaO₂ are under compressive stress. Further structural characterization and defect analysis of nonpolar ZnO material was performed using transmission electron microscopy.     

ZnO-Sn:ZnO core-shell nanowires and ZnO-Zn2SnO4 comb-like nanocomposites

Novel single-crystalline ZnO-Sn:ZnO (SZO) core-shell nanowires and ZnO-Zn2SnO4 (ZTO) comb-like nanocomposites were synthesized by thermal chemical vapor deposition at a low temperature of 650 degrees C. Scanning electron microscopy and transmission electron microscopy show the diameters and lengths of the core-shell nanowires are in ranges of 25-60 nm and 300-500 nm, respectively. The atomic ratios of Sn to (Zn + Sn) in the central and shell parts of the nanowire are 0.4 at.% and 6.1 at.%, respectively. The ZnO-ZTO comb-like nanocomposites possess ZnO nanocombs with ZTO nano-layers deposited on both sides of them. The ZnO branches and ZTO layers are single-crystalline wurtzite and spinel structures growing along the [0002] and [111] directions, respectively. Room-temperature cathodoluminescence measurements show the nanocomposites exhibit strong ultraviolet (UV) emissions at 300, 384 nm, and a broad green emission. The novel luminescence shows promising singularity for opto-electronic applications.     

Growth of zinc oxide nanorods, tetrapods, and nanobelts without catalyst

Zinc oxide (ZnO) nanostructures with various morphologies have been synthesized without catalyst in a one-step simple redox process. The results show that ZnO nanorods, nanobelts, and tetrapods with hexagonal needled arms could be synthesized via thermal treatment of a mixture of zinc oxide and charcoal powder in a muffle furnace at 1000-1200 degrees C for 240 min. XRD analyses showed that polycrystalline ZnO phase with wurtzite crystal structure was formed. At a relatively low temperature, 1000 degrees C, the ZnO structure was found to be a bundle of denser nanorods. By increasing the reaction temperature to 1100 degrees C, tetrapod-like structures of needle-like arms with pyramidal tips were formed. With the increase of temperature up to 1200 degrees C, the morphology of ZnO nanostructures changed from nanorods and tetrapods to coalescence grains. Reaction temperature was found to be the most important experimental parameter that played an important role in controlling the mode, mechanism of growth, and formation of different ZnO morphologies.     

ZnO microstructures and nanostructures prepared by sol-gel hydrothermal technique

Zinc oxide (ZnO) is an emerging material in large area electronic applications such as thin-film solar cells and transistors. We report on the fabrication and characterization of ZnO microstructures and nanostructures. The ZnO microstructures and nanostructures have been synthesized using sol-gel immerse technique on oxidized silicon substrates. Different precursor's concentrations ranging from 0.0001 M to 0.01 M (M=molarity) using zinc nitrate hexahydrate [Zn(NO3)2. 6H2O] and hexamethylenetetramine [C6H12N4] were employed in the synthesis of the ZnO structures. The surface morphologies were examined using scanning electron microscope (SEM) and atomic force microscope (AFM). In order to investigate the structural properties, the ZnO microstructures and nanostructures were measured using X-ray diffractometer (XRD). The optical properties of the ZnO structures were measured using photoluminescence (PL) and ultraviolet-visible (UV-Vis) spectroscopies.     

SmB6单晶纳米结构的可控制备及场发射特性研究

作为一种典型的近藤拓扑绝缘体, 近年来六硼化钐(SmB₆)材料受到了凝聚态物理和材料科学领域研究者的广泛关注。与块体材料相比, SmB₆纳米材料由于具有更大的比表面积而拥有更为丰富的表面电子态, 因此被认为是一个研究表面量子效应和物理机制的理想平台。由于场发射电流主要来源于纳米材料的表面态, 所以研究SmB₆纳米材料的场发射特性可以为研究其表面量子特性提供有益的参考。本研究利用化学气相沉积法, 通过控制实验条件在硅衬底上分别实现了SmB₆纳米带和纳米线薄膜的生长。研究结果表明: 所制备的SmB₆纳米线和纳米带分别为沿着[100]和[110]方向生长的立方单晶结构。场发射特性的测试结果发现: SmB₆纳米带薄膜的开启电场为3.24 V/μm, 最大电流密度达到了466.16 μA/cm ², 其场发射性能要优于纳米线薄膜。同时考虑到SmB₆拥有很低的电子亲和势、高电导率和丰富的表面电子态, 所以若可以进一步提高其场发射特性, 那么很可能在冷阴极电子源领域有潜在应用。