氧化锌纳米带中的面缺陷

面缺陷是纳米带中非常普遍和非常重要的一类缺陷.在有些情况下,面缺陷对于高表面能指数面的出现起着决定性的作用, 同时,它们可以诱导纳米带沿着特殊的方向生长.面缺陷可以是孪晶或双晶,层错和由杂质原子聚集在特定原子面所形成的间隙原子层.在本文中,利用透射电子显微术,我们将介绍氧化锌纳米带中被发现的几种面缺陷.我们确认了两种孪晶/双晶结构,它们的孪晶面分别是(0113)和(2112)面.基面层错有I1 和I2两种.在大尺寸的纳米带中,I1基面层错可以折叠到(2110)面形成棱面层错.当少量的In离子掺入氧化锌纳米带后,我们发现伴随着杂质In在基面的聚集,形成了两种倒反畴界.     

氧化锌纳米带中的面缺陷

面缺陷是纳米带中非常普遍和非常重要的一类缺陷。在有些情况下，面缺陷对于高表面能指数面的出现起着决定性的作用。同时。它们可以诱导纳米带沿着特殊的方向生长。面缺陷可以是孪晶或双晶，层错和由杂质原子聚集在特定原子面所形成的间隙原子层。在本文中。利用透射电子显微术，我们将介绍氧化锌纳米带中被发现的几种面缺陷。我们确认了两种孪晶／双晶结构，它们的孪晶面分别是（01^-13）和（^-2112）面。基面层错有I1和I2两种。在大尺寸的纳米带中，I1基面层错可以折叠到（2^110）面形成棱面层错。当少量的In离子掺入氧化锌纳米带后，我们发现伴随着杂质In在基面的聚集，形成了两种倒反畴界。     

合金催化制备氧化锌纳米双晶薄片及其结构表征 (cited: 1)

借助气相输运凝结方法,采用Ag_xAu_1-x合金作为催化剂,在较低的650 oC下成功制备出氧化锌纳米双晶薄片. 高分辨结构表征证实该薄片中存在{10-13}孪晶界面. 系列地对比实验表明高的锌蒸汽浓度和Ag_xAu_1-x合金催化作用是孪晶成核的必要条件. 还发现衬底上制备出的氧化锌纳米孪晶薄片的密度可以通过合金催化剂中的银金成分比例加以调节.     

锡催化剂助生长法制备孪晶ZnO纳米线及其结构表征

用SnO和Zn的均匀混合物在高温下共烧通过VLS机制制备出孪晶ZnO纳米线的均匀结构。SEM图像显示孪晶ZnO纳米线的直径在100~200nm之间,长度在几十微米到几百微米之间的范围内,有的甚至达到了毫米级,产率也非常的高。TEM图像中ZnO孪晶纳米线顶端的金属Sn颗粒表明了孪晶结构的Sn催化生长。高分辨电子图谱显示了氧化锌纳米线孪晶结构的特征。电子衍射分析发现孪晶氧化锌的晶带轴的方向是[0110],孪晶面为(1013),并且通过明场像和暗场像分析了孪晶纳米线的晶格关系,确定了孪晶纳米线的汽-液-固(VLS)生长机制。     

晶体相场方法模拟纳米孪晶结构

应用双模晶体相场模型,模拟共格纳米孪晶结构.结果表明:球状晶粒生长成的共格孪晶片层,在共格面上的原子排列有变形,容易出现位错;条状晶粒凝固生长成的共格孪晶界,比用球状晶粒长大生成的共格孪晶界的原子排列整齐.应用晶体相场模型,可以精确计算纳米孪晶带的厚度,设计和控制带内的原子层数,实现人工操纵纳米共格孪晶片层结构,指导实验研究纳米孪晶结构及其与性能的关系.     

CVD金刚石薄膜孪晶形成的原子机理分析

采用X射线衍射技术、电子背散射衍射技术和扫描电镜分别观察了不同甲烷浓度条件下沉积的CVD自支撑金刚石薄膜的宏观织构、晶界分布和表面形貌. 研究了一阶孪晶在金刚石晶体{111}面生长的原子堆垛过程. 结果表明，由于一阶孪晶〈111〉60°的取向差关系以及{111}面的原子堆垛结构，使{111}面上容易借助碳原子的偏转沉积产生一阶孪晶. 低甲烷浓度时，碳原子倾向于在表面能较低的{111}面沉积，为孪晶的形成提供了便利，且高频率孪晶使薄膜织构强度减弱. 甲烷浓度升高使生长激活能较小的{001}面成为主要前沿生长面，因而只有〈001〉晶向平行薄膜法向的晶粒能够不断长大，因此孪晶形核概率明显减小. 另外，在薄膜中发现二阶孪晶，并对二阶孪晶的形成进行了分析. 关键词： 金刚石薄膜 孪晶 原子机理 取向差     

C轴LiNbO_3晶体中的旋转孪晶

晶体中的孪晶,按其孪生对称元素一般分为反映和旋转孪晶两类.在LiNbO3晶体中,多数孪晶是反映孪晶. 本文所述的LiNbO3孪晶与常见的孪晶不同。它是从固-液同成分配方熔体中沿C轴方向提拉的.新晶是在原晶脊的晶面开始成核,沿着该晶面延伸发育,并与C轴斜交贯穿晶体(见图1). 这种少见孪晶的孪生对称元素是什么?它究竟属于哪类孪晶?我们采用X射线背射劳厄法和腐蚀法.对这些问题进行了比较详细的分析与讨论. 一、实 验 沿垂直拉晶方向将孪晶棒平行切割成三块晶片(图1中的α,β.γ), 每片都有原晶和新晶两部分。并分别用互和立表示.在各片I部分…     

氧化锌叶片状纳米晶的结构和光谱特性

熔盐法对sol-gel法生成的前驱物处理合成新颖的叶片状的氧化锌纳米结构,TEM照片显示其长度300-500nm,宽度为50-80nm,两头尖端约呈25°夹角,形状基本沿中轴呈中心对称。其生长过程进行了研究:弯曲了的ZnO纳米棒闭合形成框架结构,框架内沿中轴方向并排生长的ZnO纳米线填满框架内的空隙形成叶片状的氧化锌纳米结构。Raman谱测量发现该结构是晶化的六角相氧化锌。对叶片状的氧化锌的声子限制效应进行了研究,并与纳米颗粒氧化锌予以比较。435cm-1的E2峰的Fano不对称具有正的Fano耦合系数。发现在585nm处出现光致发光峰,归于ZnO纳米结构中氧缺陷的作用。     

Cu掺杂ZnO纳米材料的制备及表征

利用CuO作为前驱体对ZnO进行了Cu掺杂研究,分别在不同温度下获得了ZnO纳米带及有纳米带构成的微米花状结构,对其生长机理进行了分析。并且以Cu片为衬底获得了ZnO的纳米梳以及有纳米梳构成的多层结构ZnO。XRD表明产物中只有ZnO单质相的存在,EDS证明产物中存在Cu元素。ZnO室温下的PL谱表明其UV与深能级发射强度比随Cu掺杂量的增加而变大,说明Cu的掺杂能够降低ZnO的缺陷峰强度。     

界面结构对Cu/Ni多层膜纳米压痕特性影响的分子动力学模拟

金属多层膜调制周期下降到纳米级时,其力学性质会发生显著改变. Cu-Ni晶格失配度约为2.7%,可以形成共格界面和半共格界面,实验中实现沿[111]方向生长的调制周期为几纳米且具有异孪晶界面结构的Cu/Ni多层膜,其力学性质发生显著改变.本文采用分子动力学方法对共格界面、共格孪晶界面、半共格界面、半共格孪晶界面等四种不同界面结构的Cu/Ni多层膜进行纳米压痕模拟,研究压痕过程中不同界面结构类型的形变演化规律以及位错与界面的相互作用,获取Cu/Ni多层膜不同界面结构对其力学性能的影响特征.计算结果表明,不同界面结构的样品在不同压痕深度时表现出的强化或软化作用机理不同,软化机制主要是由于形成了平行于界面的分位错以及孪晶界面的迁移,强化机制主要是由于界面对位错的限定作用以及失配位错网状结构与孪晶界面迁移时所形成的弓形位错之间的相互作用.     

Evidences dominating the formation of ZnO nanostructures via in-situ study in an environmental scanning electron microscope

In order to well understand the growth mechanism of the diverse morphology of the ZnO nanostructures, in situ analysis of the formation of different ZnO nanostructures, such as nanowires, nanocombs, and nanosheets, has been conducted in an environmental scanning electron microscope (ESEM). It is found that both nanocombs and nanosheets grew in two-stage heating processes on parent nanowires. The difference is that the nanocombs were synthesized in extremely high pressure of zinc vapor via a self-catalyzed vapor-liquid-solid process, while the ZnO nanosheets were grown in relatively low pressure of zinc vapor. All the growth processes were revealed in real time imaging. It is demonstrated that the change in the growth environments can influence the thickness of the ZnO polycrystalline surface of the zinc powder, which alters the pressure of the zinc vapor and in turn determines the morphology of the final nanostructures.     

Synthesis and Raman analysis of 1D-ZnO nanostructure via vapor phase growth

1D-nanostructural zinc oxide (ZnO) with different shapes have been synthesized on p-type Si(1 0 0) and glass substrates via vapor phase growth by heating pure zinc powder at temperatures between 480 and 570 °C. The different ZnO nanostructures depend on the substrates and the growth temperatures. Scanning electron microscopy and X-ray diffraction revealed that a well-aligned nanowires array, which are vertical to the substrate of Si(1 0 0) with 18 sides on their heads, but six sides on their stems, has been formed at 480 °C. Raman study on the ZnO nanostructures shows that the coupling strength between electron and phonon determined by the ratio of the second- to the first-order Raman scattering cross-sections declines with decreasing diameter of the nanowires. However, a little changes of the coupling strength in terms of the width of the nanobelts have been observed.     

Field emission and photoluminescence of ZnO nanocombs

Three kinds of new comb-shape nanostructures of ZnO have been grown on single silicon substrates without catalyst-assisted thermal evaporation of Zn and active carbon powders. The morphology and structure of the prepared nanorods are determined on the basis of field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and x-ray diffraction (XRD). The growth mechanism of the ZnO nanocombs can be explained on the basis of the vapor–solid (VS) processes. In nanocombs 1 and nanocombs 2, the comb teeth grow along [0001] and the comb stem grows along [ $01\overline{1}0$ ], while in nanocombs 3, nanoteeth grow along [ $01\overline{1}0$ ] and stem grows along [0001]. The photoluminescence and field-emission properties of ZnO nanocombs 1–3 have been investigated. The turn-on electric field of ZnO nanocombs 1–3, which is defined as the field required to producing a current density of 10 μA/cm², is 9, 7.7 and 7.1 V/μm, respectively. The field-emission performance relies not only on the tip’s radius of curvature and field enhancement factor, but also on the factor evaluating the degree of the screening effect.     

Size dependence of surface optical mode and electron–phonon coupling in ZnO nanocombs

ZnO nanocombs with different sizes are synthesized by simple thermal evaporation methods. Scanning electron microscopy and transmission election microscopy testify the growth of single crystal ZnO nanocombs along [0 0 0 2] direction. The temperature-dependent Raman spectra show that the intensity of surface optical (SO) modes in ZnO nanocombs obviously increases with declining measure temperatures. With the decrease of diameters, the frequency of SO modes shows a blue shift due to the passivation of surface states. The resonant Raman scattering shows that the strength of electron–phonon coupling increases with decreasing size. Calculated on size-dependent electron–phonon interaction energy agrees well with measured values for a large size range. The origin of electron–phonon coupling in ZnO nanocombs is also discussed.     

Ni-doped zinc oxide nanocombs and phonon spectra properties

Ni-doped comb-like zinc oxide (ZnO) semiconductor nanostructures have been synthesized by a simple chemical vapor-deposition method (CVD) at relatively low temperature. The as-synthesized ZnO nanocombs consist of an array of very uniform, perfectly aligned, evenly spaced and long single-crystalline nanobelts (nanowires) with periods of about several tens of nanometers. X-ray diffraction and Raman spectra results provide the evidence that Ni is incorporated into the ZnO lattice at Zn site. Photoluminescence spectra of the as-obtained samples have been detected, in which the incorporation of donor Ni leads to the increases of the ultraviolet emission intensity and a blueshift of emission peak. This technique can be used to prepare other semiconductors and morphology-controlled doping nanocombs.     

Novel nanostructures of ZnO for nanoscale photonics,optoelectronics, piezoelectricity,and sensing

Wurtzite-structured semiconductors such as ZnO, GaN, AlN, CdSe and ZnS are important materials for nanoscale devices. Zinc oxide, for example, is a unique material that exhibits semiconducting, piezoelectric, and pyroelectric properties. Using a solid–vapor phase thermal sublimation technique, nanocombs, nanorings, nanohelixes/nanosprings, nanobows, nanobelts, nanowires, and nanocages of ZnO have been grown under specific growth conditions. This paper is about the synthesis, structure, growth mechanisms, and potential applications of these nanostructures in optoelectronics, sensors, transducers, and biomedical science. PACS 81.07.-b; 78.67.-n; 85.35.-p     

Growth, morphology and optical properties of tris(8-hydroxyquinoline)aluminum/zinc oxide hybrid nanowires

Hybrid tris(8-hydroxyquinoline)aluminum/zinc oxide (Alq₃/ZnO) nanowires were successfully grown from a one-step solution method at very low temperature. The transformation of amorphous Alq₃ into α-phase crystalline nanowires was achieved by incorporating a certain weight fraction of crystalline ZnO nanomaterials. A growth mechanism was proposed to validate the formation of crystalline Alq₃-ZnO hybrid nanowires with the help of nucleation initiated by the ZnO nanomaterials, followed by Alq₃ molecular aggregation. Effects of temperature on the evolution of morphologies of hybrid nanowires were examined by the field-emission scanning electron microscopy (FESEM). The photoluminescence (PL) spectra of hybrid nanowires showed a significant threefold enhancement in PL intensity, along with a slight blue-shift emission, when compared to the pure Alq₃ molecules, which were attributed due to the incorporation of crystalline ZnO nanomaterials and also the shielding effect of ZnO nanomaterials to avoid the excimer formation between the Alq₃ molecules in the excited state.     

One-dimensional and quasi-one-dimensional ZnO nanostructures prepared by spray-pyrolysis-assisted thermal evaporation

One-dimensional (1D) and quasi-1D ZnO nanostructures have been fabricated by a kind of new spray-pyrolysis-assisted thermal evaporation method. Pure ZnO powder serves as an evaporation source. Thus-obtained products have been characterized by X-ray diffraction (XRD) analysis, scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), transmission electron microscope (TEM). The room temperature photoluminescence spectrum of these ZnO nanostructures is presented. The results show that as-grown ZnO nanomaterials have a hexagonal wurtzite crystalline structure. Besides nanosaws, nanobelts and nanowires, complex ZnO nanotrees have also been observed in synthesized products. The study provides a new simple route to construct 1D and quasi-1D ZnO nanomaterials, which can probably be extended to fabricate other oxide nanomaterials with high melting point and doped oxide nanomaterials.     

衬底位置对化学气相沉积法制备的磷掺杂p型ZnO纳米材料形貌和特性的影响

采用化学气相沉积方法,在无催化剂的条件下,通过改变衬底位置在Si(100)衬底上制备出了高取向的磷掺杂ZnO纳米线和纳米钉.测试结果表明,当衬底位于反应源上方1.5 cm处时,所制备的样品为钉状结构,而当衬底位于反应源下方1 cm处时样品为线状结构.对不同形貌磷掺杂ZnO纳米结构的生长机理进行了研究.此外,在ZnO纳米结构的低温光致发光谱中观测到了一系列与磷掺杂相关的受主发光峰.还对磷掺杂ZnO纳米结构/n-Si异质结I-V曲线进行了测试,结果表明,该器件具有良好的整流特性,纳米线和纳米钉异质结器件的开启电压分别为4.8和3.2 V.