碱溶液修饰硅纳米线阵列绒面

提出用碱溶液修饰硅纳米线阵列制作太阳能绒面的方法。实验中首先采用金属催化化学腐蚀法在Si(100)基底上制备了定向排列的硅纳米线阵列,然后将纳米线阵列浸入碱溶液中进行修饰,修饰时间分别为10,30,50,60,90s。通过扫描电子显微镜(SEM)对硅纳米线阵列进行形貌分析,采用太阳能测试系统附带的积分球测量纳米线阵列绒面结构的反射光谱。通过测量和分析发现硅纳线阵列在碱溶液中修饰30s时表面分布均匀,在400～1000nm波段的综合反射率低于4%。结果表明碱溶液修饰纳米线阵列的方法能够有效分散束状硅纳米线阵列,明显降低绒面的反射率,并且初步分析了碱溶液修饰硅纳米线阵列的分散机理。     

AlN纳米线宏观阵列的制备

借助二次模板法成功的合成了AlN纳米线宏观阵列,并进行了表征.主要研究CVD法制备有一定取向,直径均匀的AlN纳米线宏观阵列的过程.通过气相沉积法和利用PS球自组装模板制备了金属纳米颗粒模板;再以模板上的金属纳米颗粒作为催化剂,利用化学气相沉积在模板上合成AlN纳米线宏观阵列.借助SEM,TEM观察所得样品,AlN纳米线阵列面积约为0.3 mm×0.2 mm,直径和长度分布均匀,平均直径约为41 nm,平均长度为1.8 μm左右,分散密度和覆盖率大的六角结构AlN纳米线宏观阵列.得到了可控制备AlN纳米线 关键词： AlN纳米线阵列 模板法 CVD法 SEM     

基于直接胶体晶体刻蚀技术的高度有序纳米硅阵列的尺寸及形貌控制

以自组装单层胶体小球阵列为掩模，采用直接胶体晶体刻蚀技术在硅表面制备二维有序尺寸可控的纳米结构.在样品制备过程中，首先通过自组装法在硅表面制备了直径200nm的单层聚苯乙烯(PS)胶体小球的二维有序阵列；然后对样品直接进行反应离子刻蚀(RIE)，以氧气为气源，利用氧等离子体对聚苯乙烯小球和对硅的选择性刻蚀作用，通过改变刻蚀时间，制备出不同尺寸的PS胶体小球的有序单层阵列；接着以此二维PS胶体单层膜为掩模，以四氟化碳为气源对样品进行刻蚀；最后去除胶体球后得到二维有序的硅柱阵列.SEM和AFM的测量结果表明：改变氧等离子体对胶体球的刻蚀时间和四氟化碳对硅的刻蚀时间，可以控制硅柱的尺寸以及形貌，而硅柱阵列的周期取决于原始胶体球的直径. 关键词： 胶体晶体刻蚀 纳米硅柱阵列     

多孔阵列聚合物模板的制备

金属纳米线阵列是X射线强辐射源研究中的重要材料之一,针对物理实验对纳米线阵列结构尺寸的特殊要求,采用集束热拉伸法制备了包埋高度取向的聚苯乙烯微纳米线有序阵列的聚乙烯复合丝,经切片、选择性溶解等后处理得到多孔聚乙烯模板材料。光学显微镜及扫描电镜（SEM）观测表明,模板中的小孔呈较规则的阵列结构分布,其孔径可在200 nm到几十m之间调节,孔间距可在1 m到几十m之间调节。通过比较实验的预设值和实测值表明,该方法可以实现对模板结构尺寸的设计和控制,进而将实现对纳米线阵列的尺寸控制。     

硅纳米线尖端阵列的制备及其场发射性能研究

将银镜反应与金属催化化学刻蚀相结合,在室温附近成功地制备出了硅纳米线尖端阵列,其长度为4~7μm,中间部分的直径在100~300nm之间。该方法操作简单、高效、无毒、可控以及低成本,且不需要高温、复杂的设备,对环境也没有特殊要求。性能测试结果显示:该硅纳米材料能够有效实现电子发射,开启电场约为2.7V/μm(电流密度10μA/cm2处);硅纳米尖端阵列的场增强因子约为692,可应用在场发射器件之上。     

树形结构Si/ZnO纳米线阵列的制备及光学性能

用一种低成本的方法制备出了树形结构Si/ZnO纳米线阵列。首先在室温条件下用金属辅助化学腐蚀法在Si(100)衬底上制备了Si纳米线阵列,Si纳米线的直径尺寸及分布都很均匀,通过改变腐蚀时间,能够得到高度不同的Si纳米线阵列。利用磁控溅射在Si纳米线表面制备一层ZnO薄膜,然后利用水热法在Si纳米线阵列上生长了ZnO纳米线。通过扫描电子显微镜(SEM)、能谱分析仪(EDS)和光致发光(PL)测试对样品进行了表征。通过这种方法制备的Si/ZnO复合结构在太阳能电池、光催化等领域有潜在应用价值。     

碱液修饰对硅纳米线阵列电池光谱响应的影响

采用金属催化化学腐蚀法在p型(100)硅基底上制备了硅纳米阵列,然后用碱溶液对纳米线阵列进行修饰。分别研究了碱液修饰对硅纳米线阵列形貌、光电性质的影响。研究表明: 与绒面及纳米线阵列相比,碱修饰30 s硅纳米线阵列的表面分散均匀,反射率降低;光谱响应度显著提高,并且出现最大量子效率对应波长红移现象。最后,详细讨论了碱液修饰硅纳米线阵列电池对光谱响应的影响机制。     

硅薄膜太阳电池表面纳米线阵列光学设计

陷光结构的优化是增加硅薄膜太阳电池光吸收进而提高其效率的关键技术之一. 以硅纳米线阵列为代表的光子晶体微纳陷光结构具有突破传统陷光结构Yablonovith极限的巨大潜力. 通常硅纳米线阵列可以用作太阳电池的增透减反层、轴向p-n结、径向p-n结. 针对以上三种应用, 本文运用有限时域差分(FDTD)法系统研究了硅纳米线阵列在 300-1100 nm 波段的光学特性. 结果表明, 当硅纳米线作为太阳电池的减反层时, 周期P=300 nm, 高度H=1.5 μm, 填充率(FR)为0.282条件下时, 反射率最低为7.9%. 当硅纳米线作为轴向p-n结电池时, P=500 nm, H=1.5 μm, FR=0.55条件下纳米线阵列的吸收效率高达22.3%. 硅纳米线作为径向p-n结电池时, 其光吸收主要依靠纳米线, 硅纳米线P=300 nm, H=6 μm, FR= 0.349 条件下其吸收效率高达32.4%, 进一步提高其高度吸收效率变化不再明显. 此外, 本文还分析了非周期性硅纳米线阵列的光学性质, 与周期性硅纳米线阵列相比, 直径随机分布和位置随机分布的硅纳米线阵列都可以使吸收效率进一步提高, 相比于周期性硅纳米线阵列, 优化后直径随机分布的硅纳米线阵列吸收效率提高了39%, 吸收效率为27.8%. 本文运用FDTD法对硅纳米线阵列的光学特性进行设计与优化, 为硅纳米线阵列在太阳电池中的应用提供了理论支持.     

场发射栅孔阵列的制备

 采用硅的局部氧化技术以及湿法刻蚀技术,利用2.6 μm的光刻掩模板在n型硅片上形成了栅极孔径为1 μm的场发射阴极的栅极空腔阵列,实现了用大阵点尺寸的栅极掩模板制备较小尺寸栅孔阵列。硅的湿法刻蚀溶液采用各向同性的硝酸和氢氟酸混合溶液,刻蚀后空腔的深度和宽度均随刻蚀时间线性增加。同时,由于刻蚀溶液具有较高的Si/SiO₂ 刻蚀选择比,栅极孔径随刻蚀时间增大的速度远低于深度和宽度增大的速度,栅极孔径主要取决于掩模的尺寸和氧化层的厚度。通过选择掩模板的尺寸以及氧化层的厚度,采用局部氧化技术和湿法刻蚀技术能够制备出微米或亚微米的场发射阴极的栅极空腔阵列。     

有序银纳米线阵列的表面增强拉曼光谱研究

本文通过模板法制备了一系列不同孔径的氧化铝模板 ,并通过交流电向模板中沉积银而制成有序银纳米线阵列。以SCN- 作为探针分子 ,用H3PO4溶解模板并用共焦显微拉曼系统现场检测SERS信号。结果表明 ,SERS信号的强度随露出表面纳米线的长度的增加而变大 ,到一定程度后又逐渐减弱。这说明只有具有合适长径比的纳米线才会有最大的增强     

Fabrication of silicon wafer with ultra low reflectance by chemical etching method

A pyramid and nanowire binary structure of monocrystalline silicon wafer was fabricated by chemical etching. Much lower reflectance of silicon wafer with this structure was obtained compared with that of single pyramid or nanowaire arrays. The morphology, reflectivity and etching thickness of this structure were studied, as well as the influence on them caused by etching time and thickness of silver film. An average reflectance of 0.9% was obtained under optimized condition. The formation mechanism of silicon nanowires was explained by experimental evidence.     

Fabrication of CoFe_2O_4 ferrite nanowire arrays in porous silicon template and their local magnetic properties

CoFe_2O_4 ferrite nanowire arrays are fabricated in porous silicon templates. The porous silicon templates are prepared via metal-assisted chemical etching with gold(Au) nanoparticles as the catalyst. Subsequently, CoFe_2O_4 ferrite nanowires are successfully synthesized into porous silicon templates by the sol–gel method. The magnetic hysteresis loop of nanowire array shows an isotropic feature of magnetic properties. The coercivity and squareness ratio(M_r/M_s) of ensemble nanowires are found to be 630 Oe(1 Oe = 79.5775 A·m~(-1) and 0.4 respectively. However, the first-order reversal curve(FORC) is adopted to reveal the probability density function of local magnetostatic properties(i.e., interwire interaction field and coercivity). The FORC diagram shows an obvious distribution feature for interaction field and coercivity. The local coercivity with a value of about 1000 Oe is found to have the highest probability.     

Influence of pre-surface treatment on the morphology of silicon nanowires fabricated by metal-assisted etching

Herein we demonstrate an improved metal-assisted etching method to achieve highly dense and uniform silicon nanowire arrays. A pre-surface treatment was applied on a silicon wafer before the process of metal-assisted etching in silver nitrate and hydrogen fluoride solution. The treatment made silver ion continuously reduce on silver nuclei adherence on the silicon surface, leading to formation of dense silver nanoparticles. Silver nanoparticles acting as local redox centers cause the formation of dense silicon nanowire arrays. In contrast, an H-terminated silicon surface made silver ion reduce uniformly on the silicon surface to form silver flakes. The silicon nanowires fabricated with a pre-surface treatment reveals higher density than those fabricated without a pre-surface treatment. The volume fraction improves from 18 to 38%. This improvement reduces the solar-weighted reflectance to as low as 3.3% for silicon nanowires with a length of only 0.87 μm. In comparison, the silicon nanowires fabricated without a pre-surface treatment have to be as long as 1.812 μm to achieve the same reflectance.     

Fabrication and characterization of polycrystalline silicon nanowires with silver-assistance by electroless deposition

Single crystal silicon wafers are widely used as the precursors to prepare silicon nanowires by employing a silver-assisted chemical etching process. In this work, we prepared polycrystalline silicon nanowire arrays by using solar-grade multicrystalline silicon wafers. The chemical composition and bonding on the surface of silicon nanowire arrays were characterized by Fourier Transform Infrared spectroscope, and X-ray photoelectron spectroscope. The photoluminescence spectra of silicon nanowires show red light emissions centered around 700 nm. Due to the passivation effect of Si dangling bonds by concentrated HNO₃ aqueous solution, the photoluminescence intensities are improved by 2 times. The influences of surface chemical states on the wettability of silicon nanowire arrays were also studied. We obtained a superhydrophobic surface on the as-etched silicon nanowire arrays without surface modification with any organic low-surface-energy materials, and realized the evolution from superhydrophobicity to superhydrophilicity via surface modifications with HNO₃ solutions.     

Synthesis of thin silicon nanowires using gold-catalyzed chemical vapor deposition

Silicon nanowires were synthesized using chemical vapor deposition catalyzed by gold nanoparticles deposited on silicon substrates. Silicon nanowires grew epitaxially in 111 directions on (100)-oriented silicon substrates. For a particular set of process parameters, we observed a critical thickness of the nucleating gold film, below which nanowires could not be grown. We studied the dependence of the Au-Si alloy droplet size and size distribution on the starting gold film thickness and the annealing conditions. Increasing the Cl:Si ratio in the gas phase allowed nanowires to grow on smaller Au-Si alloy droplets. We used a modified heating sequence that deconvoluted the effect of silicon substrate consumption and gas-phase silicon supply on the Au-Si alloy formation and allowed growth of nanowires with diameters less than 20 nm. The modified heating sequence was also used to demonstrate the growth of bridging silicon nanowires with diameters less than 20 nm, which is a significant step in producing electronic devices. PACS 81.07.b; 81.15.Gh     

膜结构对金纳米线阵列表面增强拉曼散射的影响

金纳米线阵列作为表面增强拉曼散射的基底能够产生有效的增强效应,金纳米线阵列通过金线之间的电场耦合产生增强的拉曼信号。在实验中,制备出金纳米线阵列与金纳米刷,两种样品结构不同,金纳米刷的一面带有金膜。用巯基吡啶作为探针分子,金纳米刷的SERS实验显示出很好的增强效应,增强因子为106,不同位点的SERS谱具有区域不均一的特征。而相同实验条件下的金纳米线阵列的增强因子只有102。光学吸收谱表明这两种结构均发生了共振吸收增强电场,对其结构的分析表明,这两种结构具有不同的电场局域化分布,同时金纳米刷中金线上端强烈的电场耦合,这是其具有更好的增强效用的原因。同时,4-MP的表面增强拉曼谱的变化特征体现了化学增强效应的影响。     

Growth and characterization of type-II ZnO/ZnTe core-shell nanowire arrays for solar cell applications

Large area, well-aligned type-II ZnO/ZnTe core-shell nanowire arrays have been fabricated on an a-plane sapphire substrate. The ZnO nanowires were grown in a furnace by chemical vapor deposition with gold as catalyst and then were coated with a ZnTe shell on the ZnO nanowires surface by a metal-organic chemical deposition chamber. The morphology and size distribution of the ZnO/ZnTe core-shell nanowire arrays were studied by scanning electron microscopy (SEM) and the crystal structure was examined by x-ray diffraction (XRD). Transmission measurement was used to study the optical properties of the core-shell nanowires. The results indicated that the ZnO/ZnTe core-shell nanowire arrays have good crystalline quality. In addition, it was found that the nanowire arrays have good light absorption characteristics and these properties make it suitable for making photovoltaic devices.     

Optimization of porous silicon preparation technology for SERS applications

A series of porous silicon samples prepared at different etching parameters, namely etchant composition, etching time and current density, was investigated as substrates for surface-enhanced Raman scattering (SERS). Silver nanostructures were deposited on porous silicon by immersion plating method and Rhodamine 6G was used as analyte. The relation between the etching parameters, morphology of porous silicon surface and its SERS efficiency after silver deposition is examined. We show that a high HF content in the etchant allows the formation of a film with close-packed silver nanocrystals, which possess strong surface enhancement properties.     

Photoluminescence origin of lightly doped silicon nanowires treated with acid vapor etching

In this work, we carry out a comprehensive photoluminescence (PL) study to elucidate the origin of light emission from porous silicon nanowires (pSiNWs). SiNWs were first grooved in lightly doped Si wafer by silver assisted chemical etching, and then treated with an acid vapor emanating from HF/HNO₃ aqueous solution heated at 60 °C. Scanning and transmission electron microscopies were used to investigate the effect of the acid vapor etching on morphological properties of SiNWs. The as prepared pSiNWs exhibited a strong room temperature PL emission centered at 1.93 eV. An increase of the PL intensity was observed with the increase of HNO₃ in the acid solution. By varying the laser excitation density from 60 to 300 W/cm², we shed the light on the radiative recombination modes occurring within the Si nanocrystals (SiNCs) generated along the pSiNWs. We study as well the temperature-dependent PL of the pSiNWs in the range 10 to 300 K. Based on both laser excitation density and temperature-dependent PL, we propose a multilevel transition scheme resuming the PL origin taking into account the size distribution, shape and surface states of the SiNCs trimming the wire sidewalls.