TEM observations of Au and Ir particles supported on CeO2

Au/CeO2 and Ir/CeO2 catalysts were observed by a transmission electron microscope in order to investigate the nano-structures of Au and Ir particles and CeO2 grains and the interface structure between metallic particles and CeO2. An annular dark field scanning transmission electron microscope (ADF-STEM) and an energy dispersive X-ray spectroscopy (EDS) revealed that the metallic particles smaller than 2 nm in diameter are highly dispersed on CeO2 supports in both catalysts. For model samples of larger CeO2 particles with flat facets of low-index surfaces, high resolution transmission electron microscopy observations of Au/CeO2 and Ir/CeO2 interfaces were made and the epitaxial relationship between Au and CeO2, (111)[110]Au//(111)[110]CeO2 has been found for the first time.     

TEM and HAADF-STEM study of a Au catalyst supported on a TiO2 nano-rod

Gold nanoparticles were deposited on TiO2 nano-rods by a deposition precipitation method. This Au/TiO2 nano-rods catalyst is active for CO oxidation even at temperatures less than 273K and is as active as the catalyst of Au supported on conventional TiO2 particles. Transmission electron microscopy (TEM) showed that the TiO2 nano-rods were composed of a single anatase crystal and had a pillar shape with an axis along the <111> direction surrounded by flat four [101] planes. High angle annular dark field scanning TEM (HAADF-STEM) also revealed that a Au platelet with a thickness of 0.5-1 nm was formed at the interface between TiO2 nano-rods. The Au platelet was not observed when conventional round particles of TiO2 were used as a support.     

Structural analyses by TEM of iridium deposited on TiO2 powder and rutile single crystal

It was found by transmission electron microscopy (TEM) that deposition precipitation of Ir onto TiO2 powder (Degussa P-25) produced Ir particles preferentially on the rutile phase. Iridium oxide particles supported on rutile TiO2 single crystal by deposition precipitation were also observed by TEM and scanning electron microscopy, and were found to exist as thin films of a few atoms. A structural change caused by hydrogen reduction was observed using high-resolution TEM and this was confirmed to be the iridium oxide film being reduced to metallic iridium particles.     

Ba_(0.99)Nd_(0.01)TiO_3纳米颗粒的合成及其光学性能研究

用熔盐法合成了掺Nd钛酸钡(Ba0.99Nd0.01TiO3)纳米颗粒,用X射线衍射、透射电镜和拉曼光谱研究了所制Ba0.99Nd0.01TiO3纳米颗粒的晶体结构,讨论了Nd掺杂对BaTiO3结构的影响,并分析了纳米颗粒的紫外–可见光吸收和光致发光性能。结果表明:合成的纳米颗粒是单晶的四方结构,平均粒径约为200 nm,光学带隙为3.23 eV。在近红外波段900 nm和1 060 nm附近有强烈发光,其分别是由Nd3+的4F3/2→4I11/2和4F3/2→4I13/2跃迁辐射导致。     

Au/STO/Pt三明治结构阻变存储器性质研究

采用脉冲激光沉积法(PLD)在Pt衬底(Pt/TiO2/SiO2/Si)上制备了SrTiO3(STO)薄膜,并对其表面特性,表面组成和结构进行了研究分析。在此基础上制备了具有三明治结构的Au/STO/Pt阻变器件,并测试了其I-V特性。结果显示:空间电荷限制电流(SCLC)机制对SrTiO3薄膜中氧空位的运输起了决定作用;薄膜界面缺陷对载流子的俘获与去俘获导致了SrTiO3薄膜I-V特性的产生。     

TiO2‐Based Composite Nanotube Arrays Prepared via Layer‐by‐Layer Assembly

A simple and versatile technique has been developed to prepare TiO₂ and TiO₂‐based composite (TiO₂–CdS and TiO₂–Au) nanotube arrays. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy‐dispersive X‐ray (EDX) analysis, X‐ray diffraction (XRD), thermogravimetric analysis (TGA), UV‐vis spectroscopy, and photoluminescence (PL) spectroscopy are used to characterize their morphology, structure, composition, and properties. The TiO₂–CdS nanotubes contained many TiO₂ and CdS quantum dots and exhibited a novel PL band in the blue‐wavelength range. The reported strategy will be useful for fabricating nanoparticle–nanoparticle composite nanostructure arrays, which are suitable for applications in catalysis, chemical sensors, nanoelectrodes, and nanodevices.     

Electron holographic 3-D nano-analysis of Au/TiO2 catalyst at interface

Three-dimensional (3-D) nanostructures of gold catalysts supported on TiO2 were analysed by electron holography and high-resolution electron microscopy. The contact angle of the gold particle on TiO2 tended to be >90 degrees in the case of gold particles with a size (height) of >4 nm and it tended to be <90 degrees for gold particles with a height of <2 nm. The change in morphology increases the perimeter at the Au/TiO2 interface as the particle size decreases. This change in 3-D structure should be attributed to a change in electronic structure at the interface. It was found that electron holography enabled 3-D analysis at the atomic level and was effective for analysing nanostructured particles.     

Enhanced Photoelectrochemistry in CdS/Au Nanoparticle Bilayers

Three different configurations of Au‐nanoparticle/CdS‐nanoparticle arrays are organized on Au/quartz electrodes for enhanced photocurrent generation. In one configuration, Au‐nanoparticles are covalently linked to the electrode and the CdS‐nanoparticles are covalently linked to the bare Au‐nanoparticle assembly. The resulting photocurrent, φ = 7.5 %, is ca. 9‐fold higher than the photocurrent originating from a CdS‐nanoparticle layer that lacks the Au‐nanoparticles, φ = 0.8 %. The enhanced photocurrent in the Au/CdS nanoparticle array is attributed to effective charge separation of the electron–hole pair by the injection of conduction‐band electrons from the CdS‐ to the Au‐nanoparticles. Two other configurations involving electrostatically stabilized bipyridinium‐crosslinked Au/CdS or CdS/Au nanoparticle arrays were assembled on the Au/quartz crystal. The photocurrent quantum yields in the two systems are φ = 10 % and φ = 5 %, respectively. The photocurrents in control systems that include electrostatically bridged Au/CdS or CdS/Au nanoparticles by oligocationic units that lack electron‐acceptor units are substantially lower than the values observed in the analogous bipyridinium‐bridged systems. The enhanced photocurrents in the bipyridinium‐crosslinked systems is attributed to the stepwise electron transfer of conduction‐band electrons to the Au‐nanoparticles by the bipyridinium relay bridge, a process that stabilizes the electron–hole pair against recombination and leads to effective charge separation.     

纳米薄膜的光学参数及厚度提取方法研究

采用磁控溅射法在玻璃基底上分别制备了不同厚度的单层TiO2、Au纳米薄膜和双层TiO2/Au纳米薄膜,并测量了这些薄膜的透射光谱.通过设计计算机程序拟合透射光谱;获取了薄膜的折射率和消光系数随波长的变化曲线以及薄膜的厚度.这种拟合方法是以非线性约束优化理论为基础的,具有透射光谱易测量、计算精度高等特点.     

石英基多层纳米TiO2-FeOOH复合材料的制备和 显微结构的表征

以石英玻璃片为基底,利用自组装技术在TiCl4-HCl体系中生长纳米TiO2,与在Fe(NO3)3-HNO3体系中生长纳米FeOOH制备负载型多层不同层序FeOOH-TiO2纳米复合薄膜光催化材料.高分辨透射电镜(HRTEM)表征结果显示:复合膜由纳米锐钛矿和针铁矿构成.UV-Vis表征结果显示:TiO2与FeOOH间的复合使TiO2吸收带均发生一定程度的红移,其中FeOOH/TiO2/FeOOH/TiO2和FeOOH/TiO2/FeOOH复合薄膜的吸收带分别为490 nm和498 nm;在以罗丹明B溶液为模拟废水的光催化实验中发现:负载FeOOH/TiO2/FeOOH/TiO2和FeOOH/TiO2/FeOOH的两种复合薄膜材料的光催化效果最佳;并且FeOOH膜在复合膜最外层比TiO2膜在最外层时光解效率高.具有一定吸附能力的针铁矿薄膜与TiO2薄膜的复合优化了复合膜内部微孔结构,促进两者间形成了积极地吸附-光催化耦合增强效应.     

In situ high-resolution transmission electron microscopy of photocatalytic reactions by excited electrons in ionic liquid

A transmission electron microscope (TEM) sample for observing photocatalysis in a liquid was prepared by using N,N,N-trimetyl-N-propylammonium-bis(trifluoromethanesulfonyl)imide. The ionic liquid (IL) was used as a reaction solvent. Tetrachloroauric acid was dissolved in the IL as gold ion species. Rutile particles were added in the solution as a photocatalyst. The low vapor pressure of the IL enables a diffusing system in high vacuum of TEM. Rutile particles were UV irradiated in that liquid phase. After 3 h UV irradiation, a gold particle of 8 nm diameter was grown on the TiO2 surface. Photonucleation of Au/TiO2 system was discussed from the high-resolution TEM images.     

WO3 passivation layer-coated nanostructured TiO2: An efficient defect engineered photoelectrode for dye sensitized solar cell

Major loss factors for photo-generated electrons due to the presence of surface defects in titanium dioxide (TiO2) were controlled by RF-sputtered tungsten trioxide (WO3) passivation.X-ray photoelectron spectroscopy assured the coating of WO3 on the TiO2 nanoparticle layer by showing Ti 2p,W 4f and O 1 s characteristic peaks and were further confirmed by X-ray diffraction studies.The coating of WO3 on the TiO2 nanoparticle layer did not affect dye adsorption significantly.Dye sensitized solar cells (DSSCs) fabricated using WO3-coated TiO2 showed an enhancement of ～10％ compared to DSSCs fabricated using pristine TiO2-based photo-electrodes.It is attributed to the WO3 passivation on TiO2 that creates an energy barrier which favored photo-electron injection by tunneling but blocked reverse electron recombination pathways towards holes available in highest occupied molecular orbital of the dye molecules.It was further evidenced that there is an optimum thickness (duration of coating) of WO3 to improve the DSSC performance and longer duration of WO3 suppressed photo-electron injection from dye to TiO2 as inferred from the detrimental effect in short circuit current density values.RF-sputtering yields pinhole-free,highly uniform and conformal coating of WO3 onto any area of interest,which can be considered for an effective surface passivation for nanostructured photovoltaic devices.     

Anodic formation of aligned and bamboo-type TiO2 nanotubes at constant low voltages

Bamboo-type TiO2 nanotubes with a highly ordered structure on titanium surface were synthesized by a self-assembly electrochemical anodization in viscous glycerol solution at constant low voltages. Field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) were used to characterize the structure and morphology of the bamboo-type TiO2 nanotubes. The experimental results show that the morphologies of the nanotubes are markedly influenced by the viscosity (the water content) of the electrolytes solution, the anodization voltage and the anodization time. Besides, a possible formation mechanism for the bamboo-type TiO2 nanotubes was proposed.     

Si/Ge异质结构的生长与特性

<正> 近年来,由Ge,Si这两种晶格失配(4.2％)材料组成的Ge/Si异质结构与Ge/Si应变超晶格,由于共具有重要的科学与技术价值,受到了人们高度重视。分子束外延(MBE)技术已成功地用于生长Ge/Si异质结构和超薄Ge/Si超晶格以及GexSi1-x/Si超晶格。化学汽相淀积技术(CVD)与MBE相比,除了设备简单、价格便宜外,对于Ge,Si外延来说,还便于与现有的硅大规模集成工艺技术相结合,使之更富有实用性。近期已有报道用CVD技术生长GexSi1-x/Si异质结构。     

MEOMS封装的锗窗金属化结构界面特性研究

基于微光机电系统对真空封装的要求,采用磁控溅射法在锗窗口上制备不同膜系的金属化结构,研究在相同的热处理条件下,不同膜系结构对锗窗口界面特性的影响。采用俄歇电子能谱分析原子在膜层间和膜基间的扩散行为。采用划痕测试仪分析膜基间的力学性能。结果表明:Ni元素对Au元素的阻挡效果明显,Cr/Ge的界面扩散剧烈。Cr/Ni/Au金属化结构的膜基结合力为14N,优于其他膜系结构,对于提高锗窗膜基结合强度效果最显著。     

沉积在硅纳米孔柱阵列上的金网络

采用浸渍技术在硅纳米孔柱阵列(Si-NPA)衬底上沉积了金(Au),得到了Au的网络结构Au/Si-NPA。测试分析表明,将Au/Si-NPA进行600℃氧退火60min,退火前后的Au晶粒度分别为26.0nm和75.5nm。无论是在氧气还是在氮气气氛下对Au/Si-NPA进行600℃退火,Au都不会渗透到Si-NPA衬底内,而且也不会与硅反应形成化合物。说明Au可作为良好的互连材料应用到超大规模集成电路中。     

KrF脉冲激光退火制备锐钛矿TiO2薄膜

在常温下,用射频磁控溅射在石英衬底上沉积厚度约为200 nm 的TiO2薄膜,然后使用波长为248 nm 的KrF脉冲激光器,在不同功率密度下对薄膜样品进行辐照退火处理,并采用X射线衍射（XRD)、拉曼(Raman)、X射线电子能谱（XPS）、原子力显微镜(AFM)、扫描电子显微镜(SEM)、高分辨率扫描隧道显微镜（HRTEM）以及选择区域电子衍射（SAED）、紫外可见分光光度计等方法分析不同激光功率密度退火对TiO2薄膜的结构、表面形貌和透射率等性能的影响。结果表明当激光功率密度为0.5 J/cm2时,可获得高质量的锐钛矿TiO2薄膜,当继续增大光功率密度时,TiO2薄膜变为(1 1 0)取向的金红石相,其薄膜表面粗糙度也相应增大。     

Formation of Gold and Silver Nanoparticle Arrays and Thin Shells on Mesostructured Silica Nanofibers

Mesostructured silica nanofibers synthesized in high yields with cetyltrimethylammonium bromide as the structure‐directing agent in HBr solutions are used as templates for the assembly of Au and Ag nanoparticles and the formation of thin Au shells along the fiber axis. Presynthesized spherical Au and Ag nanoparticles are adsorbed in varying amounts onto the silica nanofibers through bifunctional linking molecules. Nonspherical Au nanoparticles with sharp tips are synthesized on the nanofibers through a seed‐mediated growth approach. The number density of nonspherical Au nanoparticles is controlled by varying the amount of seeded nanofibers relative to the amount of supplied Au precursor. This seed‐mediated growth is further used to form continuous Au shells around the silica nanofibers. Both the Au‐ and Ag‐nanoparticle/silica‐nanofiber hybrid nanostructures and silica/Au core/shell fibers exhibit extinction spectra that are distinct from the spectra of Au and Ag nanoparticles in solution, indicating the presence of new surface plasmon resonance modes in the silica/Au core/shell fibers and surface plasmon coupling between closely spaced metal nanoparticles assembled on silica nanofibers. Spherical Au‐ and Ag‐nanoparticle/silica‐nanofiber hybrid nanostructures are further used as substrates for surface‐enhanced Raman spectroscopy, and the enhancement factors of the Raman signals obtained on the Ag‐nanoparticle/silica‐nanofiber hybrid nanostructures are 2 × 10⁵ for 4‐mercaptobenzoic acid and 4‐mercaptophenol and 7 × 10⁷ for rhodamine B isothiocyanate. These hybrid nanostructures are therefore potentially useful for ultrasensitive chemical and biological sensing by using molecular vibrational signatures.     

Increasing emission current from MIM cathodes by using an Ir-Pt-Aumultilayer top electrode

We investigated the effect of the top electrode materials on the electron emission and durability of metal-insulator-metal (MIM) cathodes. The durability is improved when high sublimation-enthalpy material, such as Ir, Mo, or W, are used; however, the emission current, and the transfer ratio, decrease. The material dependence of the transfer ratio is shown to be dominated by the scattering probability of hot electrons in the metal. The scattering probability was estimated from the metal's density-of-states, or more simply, from the number of d-electrons. We found that the multilayer top electrode consisting of Ir, Pt, and Au provides the best top electrode combination for MIM cathodes. The high sublimation-enthalpy Ir layer, which is in contact with the insulator, acts as a barrier metal and improves the durability, whereas the surface Au layer maintains the transfer ratio at a high value. With this top electrode structure, emission current density is increased to 5.8 mA/cm², which is sufficient for field-emission displays. We demonstrated a display consisting of a 30×30-dot MIM cathode-array with the multilayer top electrodes     

退火对Pt/TiO2肖特基二极管结构及电学性能的影响

以硅为衬底,采用射频磁控溅射技术制备了TiO2薄膜,利用扫描电子显微镜及拉曼光谱对退火前后的TiO2进行表征与结构分析.结果表明,退火后的TiO2具有良好的结晶特性,且呈锐钛矿结构.在此薄膜工艺条件下,以TiO2为半导体层在玻璃基底上制备了Al/TiO2/Pt肖特基二极管,并在153～433 K温度范围内对其进行了I-V测试,得到以下结果:在整个温度范围内,A1/TiO2/Pt肖特基二极管均表现出良好的整流特性;其理想因子随温度升高而降低,势垒高度随温度升高而升高;在433 K下,理想因子为1.31,势垒高度为0.73,表明此肖特基二极管已接近理想的肖特基二极管.