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.     

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     

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     

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。     

硅纳米线阵列的光学特性

在常温常压条件下,采用改进的金属催化化学腐蚀方法在n型单晶硅片(100)上制备了大面积垂直于硅衬底、直径均匀、排列整齐的硅纳米线阵列。分析了样品的表面形貌和反射谱,纳米线直径为10~50 nm。在腐蚀时间分别为15,30,60 m in时,纳米线长度分别为9,17,34μm。样品的减反射性能优异,在300~1 000nm波段,得到了2.4%的反射率。初步分析了纳米线阵列的减反射机制和不同腐蚀时间样品的反射率差异。     

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     

用PAA模板法实现硅基纳米孔阵列结构

用二次阳极氧化方法制备出分立、双向贯通并且超薄（500—1000 nm）的多孔阳极氧化铝膜,贴合到硅片上进行干法刻蚀,实现图形转移,得到了硅基纳米孔阵列结构,并对工艺中影响图形转移质量的因素进行了探索.扫描电镜（SEM）测试结果表明该途径得到的纳米结构孔形态均匀且大面积有序,孔深度可达到125 nm.对该样品进行热氧化处理后进行光致发光（PL）测试,结果表明其光致发光机理是基于通常较微弱的TO声子辅助的硅带边发光,并实现了显著发光增强,对这种增强效果的物理机理进行了理论分析.该结构具有的独特光学特性为利用 关键词： 多孔阳极氧化铝模板 硅基纳米孔阵列结构 图形转移     

镍掺杂硅纳米线电子结构和光学性质的第一性原理研究

利用基于密度泛函理论的第一性原理计算,对镍掺杂硅纳米线的结构稳定性、电子与光学性质进行了研究.结果表明:Ni容易占据硅纳米线表面的替代位置.镍掺杂后的硅纳米线引入了杂质能级,杂质能级主要来源于Ni的3d电子的贡献.由于Ni的3d态和Si的3p态的耦合作用,使禁带宽度变窄.掺杂后的硅纳米线在低能区出现了一个较强的吸收峰,且吸收带出现宽化现象. 关键词： 硅纳米线 掺杂 电子结构 光学性质     

P掺杂硅纳米管电子结构与光学性质的研究

采用基于密度泛函理论的第一性原理计算,研究了P掺杂对单壁扶手型硅纳米管电子结构和光学性质的影响.结果表明:经过P掺杂,单壁扶手型硅纳米管的能带结构从间接带隙变为直接带隙,其价带顶主要由Si-3p态电子构成,导带底主要由Si-3p态电子和Si-3s态电子共同决定;同时通过P掺杂,使单壁扶手型硅纳米管的禁带宽度变窄,导电性增强,吸收光谱产生红移.研究结果为硅纳米管在光电器件方面的应用提供了理论基础.     

Cu/AAO纳米有序阵列复合结构的光学特性研究

用电化学方法制备了Cu/AAO纳米有序阵列复合结构,实验研究了该结构的光吸收与光致发光特性。结果表明,植入阳极氧化铝模板中Cu纳米粒子对结构的光吸收和光致发光影响非常敏感。即随着Cu沉积量的增加,致使该复合结构的吸收边大幅度红移,从近紫外至近红外其最大频移量可超过500 nm;同时还伴随使阳极氧化铝模板的光致发光峰位稍有蓝移、强度逐渐削弱直至猝灭的过程。分析了Cu纳米粒子使Cu/AAO复合结构出现上述现象的原因。     

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.     

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.     

Growth process and mechanism of a multi-walled carbon nanotube nest deposited on a silicon nanoporous pillar array

A large scale nest array of multi-walled carbon nanotubes (NACNTs) was grown on silicon nanoporous pillar array (Si-NPA) by thermal chemical vapor deposition. Through observing its macro/micromorphology and structure, ascertaining the catalyst component and its locations at different growth time by hiring field emission scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, and selected area electron diffraction, the growth process was deduced. Its thermal properties were also investigated by using a thermogravimetric analyzer. Our experiments demonstrated that the CNTs growth by means of root-growth mechanism at the initial growth stage, then a continuous growth process with its tip open is suggested, finally, a schematic growth model of NACNT/Si-NPA was presented.     

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.     

Improved surface-enhanced Raman scattering of patterned gold nanoparticles deposited on silicon nanoporous pillar arrays

Large-area silicon nanoporous pillar arrays (Si-NPA) uniformly coated with gold nanoparticles was synthesized, and surface-enhanced Raman scattering of rhodamine 6G adsorbed on these gold nanoparticles were studied and compared. It's found that Au/Si-NPA substrate has a significantly high Raman signal sensitivity and good homogeneity. These are attributed to gold nanoparticles with narrow particle-size distribution uniformly coated on the surface and to the enlarged specific surface area for adsorption of target molecules brought by the porous silicon pillars.     

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.