碳纳米管/硅纳米孔柱阵列的场发射性能

"通过热化学气相沉积的方法将碳纳米管生长到硅纳米孔柱阵列衬底上．采用场发射扫描电子显微镜、透射电子显微镜、高分辨透射电子显微镜、拉曼光谱和X射线能谱对所制备的样品形貌、组成进行了分析．结果发现：所制备产物为一种具有面积大、准周期性的碳纳米管/硅巢状阵列复合结构．能谱分析表明碳纳米管仅含有碳元素．对样品进行场发射性能测试表明该结构开启电压为1.3 MV/m,当外加电压为4.26 MV/m,发射电流为5 mA/cm2．由FN公式计算相应的场增强因子约为1.1￡104．碳纳米管/硅纳米孔柱阵列好的场发射性能被归     

SERS activity of Au nanoparticles coated on an array of carbon nanotube nested into silicon nanoporous pillar

A novel composite structure, Au nanoparticles coated on a nest-shaped array of carbon nanotube nested into a silicon nanoporous pillar array (Au/NACNT/Si-NPA), was fabricated for surface-enhanced Raman scattering (SERS). The morphology of the Au/NACNT/Si-NPA composite structure was characterized with the aid of scanning electron microscopy, X-ray diffraction instrumentation and Transmission electron microscopy. Compared with SERS of rhodamine 6G (R6G) adsorbed on SERS-active Au substrate reported, the SERS signals of R6G adsorbed on these gold nanoparticles were obviously improved. This was attributed to the enlarged specific surface area for adsorption of target molecules brought by the nest-shaped CNTs structure.     

Influence of growth time on field emission properties from carbon nanotubes deposited on arrayed nanoporous silicon pillars

We investigated the influence of growth time on field emission properties of multi-walled carbon nanotubes deposited on silicon nanoporous pillar array (MWCNTs/Si-NPA), which were fabricated by thermal chemical vapour deposition at 800 °C for 5, 15 and 25 min respectively, to better understand the origins of good field emission properties. The results showed that the MWCNTs/Si-NPA grown for 15 min had the highest field emission efficiency of the three types of samples. Morphologies of the products were examined by field-emission scanning electron microscope, and the excellent field emission performance was attributed not only to the formation of a nest array of multi-walled carbon nanotubes, which would largely reduce the electrostatic shielding among the emitters and resulted in a great enhancement factor, but also to the medium MWCNTs density films, there was an ideal compromise between the emitter density and the intertube distance, which also could effectively avoid electrostatic shielding effects, along with a high emitter density.     

Preparation, structural and electrical properties of zinc oxide grown on silicon nanoporous pillar array

Polycrystalline thick film of zinc oxide (ZnO) is grown on a unique silicon substrate with a hierarchical structure, silicon nanoporous pillar array (Si-NPA), by using a vapour phase transport method. It is found that as-grown ZnO film is composed of closely packed ZnO crystallites with an average size of $\sim$10\,\mu$m. The film resistivity of ZnO/Si-NPA is measured to be $\sim$8.9\Omega\cdot$\,cm by the standard four probe method. The lengthwise $I$-$V$ curve of ZnO/Si-NPA heterostructure is measured. Theoretical analysis shows that the carrier transport across ZnO/Si-NPA heterojunction is dominated by two mechanisms, i.e. a thermionic process at high voltages and a quantum tunnelling process at low voltages.     

硅纳米孔柱阵列的结构和光学特性研究

采用水热腐蚀技术在单晶硅衬底上制备出一种新的硅微米／纳米结构复合体系——硅纳米孔柱阵列(Si-NPA)，并对其表面形貌、结构及光学特性进行研究.Si-NPA的结构复合性体现为 在微米和纳米两个尺度上形成了三个分明的结构层次，即微米尺度的硅柱阵列结构、硅柱上 的纳米多孔结构以及组成孔壁的硅纳米晶粒.积分光反射谱和荧光光谱测试表明，Si-NPA具 有良好的光吸收和光致发光特性.依据Si－NPA积分反射谱的实验数据，采用Kramers-Kronig 变换关系计算得到了Si-NPA的复折射率和复介电函数、吸收系数等光学常数，并由此讨论了 Si-NPA相对于单晶硅的光学特性发生显著变化的原因.最后，通过分析Si-NPA的光吸收系数 与入射光子能量之间的关系，揭示出Si-NPA具有直接带隙半导体的电子结构特征，而且理论 计算得到的Si-NPA的带隙能与其光致发光谱的峰位能很好符合. 关键词： 硅纳米孔柱阵列 光学特性 电子结构 水热腐蚀     

一种自支撑金纳米薄膜的制备、结构和氮吸附特性

以一种新的硅微米/纳米结构复合体系——硅纳米孔柱阵列作为还原性衬底，采用浸渍技术制备出一种自支撑的金纳米薄膜，并对其表面形貌和结构进行了表征.实验表明，金纳米薄膜的制备过程是一个自终止过程.当硅纳米孔柱阵列被耗尽后，浸渍溶液中Au³⁺的还原反应将自行终止；同时，所形成的金纳米薄膜自动与衬底脱离并成为一种自支撑薄膜.薄膜的形成机理被归因于硅纳米孔柱阵列所具有的高的表面活性和还原性.用能量弥散x射线谱对薄膜表面化学成分分析的结果表明，如此制备的金纳米薄膜具有很强的氮吸附和氮储存能力.这一特性有可能在气体传感器、空气分离和氮纯化以及氮化合物的膜合成器等技术领域得到应用. 关键词： 自支撑金纳米薄膜 硅纳米孔柱阵列 浸渍技术     

Microstructure and blue photoluminescence enhancement of silicon nanoporous pillar array embedded in ferroelectric barium strontium titanate

A silicon nanoporous pillar array (Si-NPA) with micrometer/nanometer hierarchical structure was fabricated by hydrothermal etching, followed by spin-coating barium strontium titanate (BST) on Si-NPA substrate. The photoluminescence (PL) spectra of the Si-NPA and BST/Si-NPA thin film were investigated. The emission band of freshly prepared Si-NPA located at 630 nm, and a blueshift at 425 nm as well as degradation in intensity after annealing at 600 °C for 1 h was observed, which might be explained by a quantum confinement effect model. BST ferroelectric material provided a static-electric field and induced the excited carriers in Si-NPA to migrate toward the opposite direction and recombine in an interfacial oxide layer. Therefore, BST enhanced blue emission of Si-NPA as well as passivated Si-NPA.     

氧化锌/硅纳米孔柱阵列的结构和光致发光特性研究

以硅纳米孔柱阵列(Si-NPA)为衬底、用化学气相沉积法制备了具有规则阵列结构特征的ZnO/Si-NPA纳米复合体系，并对其结构和光致发光性质进行了表征. 实验结果显示，组成ZnO/Si-NPA表面阵列的每个柱子均呈现层壳结构. 不同于衬底Si-NPA的红光和蓝光发射，ZnO/Si-NPA在紫外光区和蓝绿光区呈现出两个强的宽发光峰. 分析表明，紫外光发射应归因于ZnO晶体的带边激子跃迁；而蓝绿光发射则来自于ZnO晶体本征缺陷所形成的两类深能级复合中心上载流子的辐射跃迁.     

Electronic band structure and optical properties of silicon nanoporous pillar array

Silicon nanoporous pillar array (Si-NPA) is fabricated by hydrothermally etching single crystal silicon (c-Si) wafers in hydrofluoric acid containing ferric nitrate. Microstructure studies disclosed that it is a typical micron/nanometer structural composite system with clear hierarchical structures. The optical parameters of Si-NPA were calculated by general light-absorption theory and Kramers–Kronig relations based on the experimental data of reflectance and the variations compared with the counterparts of c-Si were analyzed. The features of the electronic band structure deduced from the optical measurements strongly indicate that Si-NPA material is a direct-band-gap semiconductor and possesses separated conduction sub-bands which accords with conduction band splitting caused by silicon nanocrystallites several nanometers in size. All these electronic and optical results are due to the quantum confinement effect of the carriers in silicon nanocrystallites.     

Characterization of optoelectronic properties of the ZnO nanorod array using surface photovoltage technique

Well-aligned ZnO nanorod array, synthesized by wet chemical bath deposition (CBD) method on conductive indium-in-oxide (ITO) substrate, was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy. Surface photovoltage (SPV) technique based on a scanning Kelvin Probe system was employed to investigate the optoelectronic behavior of ZnO nanorod array. The surface photovoltage and its time-resolved evolution process are used to determine the energy level structure of the ZnO nanorod array.     

Centimetre-Long Single Crystalline ZnO Fibres Prepared by Vapour Transportation

Centimetre-long ZnO fibres are synthesized by vapour transportation via thermal evaporation of ZnO powders. The growth process is carried out in a graphite crucible, in which ZnO powder is loaded as the source material, and a silicon wafer is positioned on the top of the crucible as the growth substrate. During the growth process, the source temperature is kept at 800℃ and the substrate temperature is kept at 600℃. Typical growth time to obtain centimetre-long ZnO fibres is 5-10 hours. Scanning electron microscopy （SEM）, x-ray diffraction （XRD）, transmission electron microscopy （TEM）, and selected area electron diffraction （SAED） measurement results show that ZnO fibres are single crystalline with high crystalline quality and very low defects concentration.     

硅纳米孔柱阵列及其四氧化三铁复合薄膜的湿敏电容特性研究

报道了硅纳米孔柱阵列（Si-NPA），Fe₃O₄复合的Si-NPA（Fe ₃O₄/Si-NPA）两种薄 膜材料的制备方法并对其形貌和结构进行了表征，研究了其电容湿度传感特性.结果表明，S i-NPA，Fe₃O₄/Si-NPA均为微米/纳米结构复合体系.当环境相对湿 度从11％上升到95％ 时，采用100 Hz的信号频率进行测试，以Si-NPA和Fe₃O₄/Si-NPA 为电介质材料制成的湿 敏元件的电容增加值分别为起始值的1500％和5500％；采用1000 Hz的信号频率测试时，则 分别为起始值的800％和12000％，显示出两种材料较高的湿度灵敏性和较强的绝对电容输出 信号强度.同时，在升湿和降湿过程中，Si-NPA，Fe₃O₄/Si-NPA都 具有较快的响应速度 ，其响应时间分别为15 s，5 s和20 s，15 s.文章结合材料的形貌和结构特性对其物理机理 进行了分析.上述结果表明，Si-NPA无论是直接作为湿度薄膜传感材料还是作为复合薄膜湿 度传感材料的衬底都具有很好的前景. 关键词： 硅纳米孔柱阵列 3O₄')" href="#">Fe₃O₄ 湿度电容传感特性     

AES studies of palladium films formed on copper and mica

Thin epitaxial films of palladium were grown on epitaxial copper films and cleaved mica in ultra high vacuum. The growth modes of these films were investigated by Auger electron spectroscopy (AES), low energy electron diffraction (LEED), transmission electron microscopy (TEM), and TEM replica techniques. Layer by layer growth of Pd on Cu and mica was observed and inelastic mean free paths of Auger electrons for energies of 60 eV (Cu MMM) and 329 eV (Pd MNN) were calculated. These values were 5.7 and 6.9 Å respectively. The thermal stability of monocrystalline and polycrystalline Pd/Cu bilayer films at 483 K was also investigated by AES and TEM. It was found that Pd agglomerates on the Cu at this temperature to form a Stranski-Krastanov growth morphology. The agglomeration is much more rapid on polycrystalline films, suggesting that high surface diffusivity paths (grain boundaries and possibly other defects) enhance the surface diffusion of Pd on Cu.     

Growth Mechanism and Characterization of Single-crystalline Ga-doped SnO2 Nanowires and Self-organized SnO2/Ga2O3 Heterogeneous Microcomb Structures

Ga掺SnO2单晶纳米线和SnO2/Ga2O3自组织异质微米梳是通过简单的热蒸发沉淀法一步制得的,并通过X射线粉末衍射(XRD)、场激发扫描电子显微镜(FE-SEM)、透射电子显微镜(TEM)、X射线能量散射谱仪(EDS)、选区电子衍射谱(SAED)进行表征．从FE-SEM的图片上可以看出生成的产物具有纳米线和一种新的微米梳状形貌．XRD、SAED和EDS显示他们是单晶四角形的SnO2．产物的主干呈带状,纳米带阵列均匀的分布在主干的一侧或两侧．大量的Ga2O3纳米颗粒沉积在微米梳的表面．主干纳米带主要沿着[100]方向生长, 自组织的纳米带分支则在主干的(100)面上沿着[110]或者[110]方向生长．由于Ga的大量掺杂,光致发光谱的衍射峰发生红移并严重变宽．针对SnO2:Ga2O3异质微米梳的生长过程进行了解释,并讨论了实验条件对形貌的影响．     

电子束蒸发法在多孔氧化铝膜上制备银纳米点阵列

采用二步阳极氧化法在草酸溶液中制备了高度有序的多孔阳极氧化铝(Porous Anodic Alumina,PAA)薄膜。以多孔氧化铝薄膜为模板,采用真空电子束蒸发的方法在多孔氧化铝模板上制备出了高度有序的金属银纳米点阵列体系。扫描电镜(SEM)测试结果表明,所制备的金属银纳米点阵列与多孔阳极氧化铝膜的多孔阵列具有完全相同的有序结构,阵列中银纳米颗粒的形状接近球形,其直径大约为70nm,与氧化铝模板的孔径基本一致。研究了高度有序银纳米点阵列的形成过程。     

High-density attachment of FePt nanoparticles on carbon nanotubes by a facile microwave-assisted polyol method

High-density attachment and one-dimensional (1D) array of FePt nanoparticles (NPs) along carbon nanotubes (CNTs) surface to generate FePt/CNT nanocomposites were successfully obtained via a facile CNT-mediated microwave polyol method. The as-prepared 1D FePt/CNTs is about 10–20 nm in diameter and up to μm scale in length. By adjusting the solvents, the ratio of Fe/Pt and the attached density of FePt NPs on the surface of CNTs could be well controlled. The structures, composition, and magnetic properties of the FePt/CNTs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and magnetic measurements. The possible growth mechanism has also been proposed.     

银/硅纳米孔柱阵列活性基底的SERS效应研究

以硅纳米孔柱阵列(Si-NPA)为衬底,采用浸渍法制备出一种具有规则表面形貌特征的银/硅纳米孔柱阵列(Ag/Si-NPA),并以R6G为探测目标材料,对其表面增强拉曼(SERS)效应进行了研究。结果表明,对于R6G浓度低至10-15M,Ag/Si-NPA均能表现出清晰的特征SERS峰。随着浓度的降低,R6G的荧光淬灭,所测拉曼光谱的基线降低,但特征峰峰位基本保持不变。在低浓度10-15M时得到的SERS光谱,理论上证明为单分子光谱。此外,Ag/Si-NPA活性基底具有较好的稳定性,在长达28天的自然老化过程中,Ag/Si-NPA能够保持对R6G较高的探测水平,光谱具有较好的信噪比和分辨率。Ag/Si-NPA是一种理想的SERS活性基底。     

Structure transition and photoluminescence of CdS/Si nanoheterostructure array on thermal annealing

CdS/Si heterojunctions have been prepared through growing CdS nanocrystallites (nc-CdS) on the silicon nanoporous pillar array (Si-NPA) by the chemical bath deposition method. Cadmium nanocrystallites (nc-Cd) have been observed and ascribed to the reducibility of Si-NPA. The reason for the appearance of CdO is indistinct and the related work will be done in the future. The blue, green and red emissions are ascribed to the silicon oxide layer, band gap of nc-CdS and the sulphur vacancies, respectively. Redshift and blueshift with the annealing temperature about green emissions are contributed to quantum size effect and the structure transition from nc-Cd to CdO. It is beneficial for investigating the structures and defects to the application of CdS/Si in the optoelectronic field.     

One-pot synthesis of one-dimensional array Pt nanoparticles on carbon nanotubes via a facile microwave polyol method

High-density attachment and one-dimensional array Pt nanoparticles (NPs) on carbon nanotubes (CNTs) to generate Pt/CNTs heterostructures are obtained via one-pot microwave polyol method. The morphology, composition of as-obtained Pt/CNTs heterostructures is characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD). The Raman spectrum and Fourier transform infrared (FTIR) spectrum show the introduction of defects or functional groups on CNTs surface, which are crucial factors to assist the nucleation and growth of Pt NPs along the skeleton of CNTs.     

Morphology controlled solvothermal synthesis of Cd(OH)2 and CdO micro/nanocrystals on Cd foil

Cadmium hydroxide (Cd(OH)₂) and cadmium oxide (CdO) nano and micro crystals were synthesized in ethanol-water medium using cadmium foil both as a source and substrate under solvothermal condition. Different concentrations of ammonium hydroxide, hydrazine hydrate, sodium hydroxide and potassium hydroxide were added to study the structural and morphological variations in the products. Synthesis was carried out at different temperatures to study the growth stages of the nano/microstructures. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The as-prepared Cd(OH)₂ products were transformed to CdO by thermal treatment in air. The possible growth mechanism for the formation of different morphologies at different basic medium has been proposed. The optical absorption measurement was carried out to determine the values of the band gap of CdO.