纳米球刻蚀法制备的二维有序的CdS纳米阵列及其光学性质的研究

采用纳米球刻蚀(nanosphere lithography)技术,以自组装的聚苯乙烯纳米小球(polystyrene,PS小球)的单层膜为掩模,制备出二维有序的CdS纳米阵列.利用扫描电子显微镜(SEM)对样品结构进行了表征,用紫外—可见分光光度计对样品光学性质进行了分析.结果表明：制备的二维CdS纳米阵列是高度有序的,且与作为掩模的纳米小球的原始尺寸及排布结构一致;禁带宽度为2.60eV,相对于体材料的2.42eV,向短波长蓝移了0.18eV,表现出CdS材料在纳米结构点阵中的量子尺寸效应;CdS纳米 关键词： 纳米球刻蚀 二维CdS纳米有序阵列     

氧等离子体处理对GaAs表面单层自组装SiO2纳米球薄膜的影响

二维纳米阵列结构因其重要的光学性能被广泛应用于各类光电子器件。本文对自组装单层SiO2纳米球掩模刻蚀法制备GaAs纳米柱二维阵列结构的关键工艺技术进行了研究。采用旋涂法在GaAs表面制备自组装单层SiO2纳米球,重点研究了GaAs表面氧等离子体亲水处理工艺对纳米球排列特性的影响,获得最佳工艺条件为功率配比100 W+80 W、腔室压力4 Pa、氧气流量20 mL/min、处理时间1200 s,并最终得到排列紧密的大面积单层纳米球薄膜。以单层纳米球为掩模,采用感应耦合等离子体刻蚀技术在GaAs表面制备了纳米柱阵列并测试了其表面光反射谱。测试结果表明,GaAs纳米柱阵列在特定波段的反射率降低至5%,远低于表面无纳米结构的薄膜材料表面高达40%的光反射。分析表明纳米柱可以激发米氏散射共振效应,从而有效降低反射率并提升光吸收。     

聚苯乙烯多孔薄膜的密度梯度控制

利用单分散的SiO2微球自组装制备了含一种尺寸微球的SiO2胶体晶体和含多种尺寸微球的多层异质结构。对含一种尺寸微球的SiO2胶体晶体进行煅烧和刻蚀处理后,胶体晶体中空隙所占比例大于立方密堆结构的26%,形成了非密堆结构,而且刻蚀时间越长,空隙比例越大。在同样的热处理和刻蚀条件下,微球尺寸越小的胶体晶体被刻蚀的程度越高,结构中空气空隙所占的比例越大。对SiO2多层异质结构经过煅烧和刻蚀处理后,得到了空隙梯度变化的多层结构,以此为模板制备了密度梯度变化的聚苯乙烯多孔薄膜。薄膜各层之间形成了平滑的过渡,没有显示出明显的层间缺陷,且孔与孔之间没有出现3维有序多孔结构中常见的大的连通孔道。     

铬过渡层对纳米球刻蚀法制备二维银纳米结构的影响

研究了铬过渡层对纳米球刻蚀法制备二维银纳米点阵结构的影响。首先利用自组装的方法在玻璃基底上制备出单层排列的聚苯乙烯纳米球阵列,然后使用物理气相沉积的方法在二维聚苯乙烯纳米球阵列上沉积一层铬层作过渡层和银层,最后将玻璃基底在乙醇溶液中超声移除聚苯乙烯纳米球,得到二维的银纳米点阵。实验发现,随着铬过渡层厚度的增加,制得的二维银纳米点阵阵列趋于完整,单个的银纳米颗粒由椭圆状转变为三角形形状。实验中测量了所得到的二维银纳米结构的吸收光谱。     

基于Ag三角阵列的表面增强红外基底的制备

利用聚苯乙烯(PS)微米球模板技术来制备表面增强红外基底,首先在氟化钙窗片表面自组装一层PS小球,并真空蒸镀银金属。接着除掉PS小球及其顶端的银膜之后,即可在氟化钙表面制备有序的银三角阵列结构。用光学显微镜和傅里叶变换红外光谱仪(FTIR)对制备的银三角阵列基底进行了表征。结果表明,其表面等离子激元吸收在中红外波段。     

一种用于LSPR传感器的准正方型银纳米颗粒阵列制备

首先控制聚苯乙烯纳米球(PS球)乳液在基片上的干燥温度,采用自组装方法,使用单一粒径的PS球制备出单层的PS球亚稳态正方排列结构模板。然后,在模板上通过磁控溅射法沉积一层银膜。利用纳米球光刻技术,去掉PS球模板得到二维正方点阵排列的准正方形银纳米颗粒阵列结构。     

利用胶体小球掩蔽刻蚀技术制备的半导体纳米阵列的场电子发射特性

利用胶体小球掩蔽刻蚀技术,制备了单晶硅纳米阵列,利用原子力显微镜观察了硅阵列的表面形貌,实验结果表明,硅柱阵列具有高密度和较好的均匀性。同时研究了单晶硅纳米阵列的场电子发射特性。为了提高样品的场发射性能,在所制备的单晶硅有序纳米阵列上生长了一层非晶碳薄膜。与单晶纳米硅柱阵列相比,覆盖有非晶碳膜的样品的场电子发射特性有了明显的改善,表现在场发射的开启电场下降,同时场发射增强因子得到增加。结果表明非晶碳膜确实能够降低电子发射的表面有效势垒,从而增强了场电子发射特性。     

氧化钨二维微米球腔阵列对聚苯胺电致变色的影响

采用气/液界面自组装方法制备规整排列的聚苯乙烯微球二维单层结构,以此为模板,采用电化学沉积法在电极表面构筑了有序的氧化钨微球腔阵列,进一步在氧化钨球腔内电化学沉积聚苯胺,采用吸收光谱研究了电极表面球腔阵列结构对聚苯胺电致变色行为的影响.     

场发射冷阴极微栅孔阵列制备技术

实现了一种采用聚苯乙烯纳米球自组装技术和微机械制造技术加工的场发射阴极用亚微米栅极微孔阵列。设计了一套完整的工艺实验方案,首先采用微球自组装技术获得了亚微米级金属网孔掩膜,然后通过反应离子刻蚀技术获得了亚微米栅极孔阵列,从而实现了集成度高、分布均匀的周期性亚微米孔洞阵列的制备,微孔集成度达到108cm-2。实验研究了氧气刻蚀聚苯乙烯微球的规律。采用金属掩膜,四氟化碳干法刻蚀二氧化硅,获得了深度为500 nm的微孔。实验结果证明该工艺方案是一种获得大面积、均匀分布、集成度高的场发射冷阴极栅孔阵列的有效方法。     

有序金纳米颗粒阵列的制备及光吸收特性研究

采用纳米球刻蚀技术中漂移法在玻璃基片上制备较大 面积不同直径的聚苯乙烯小球掩模板, 采用磁控溅射技术在掩模板上沉积不同厚度的金薄膜, 去除聚苯乙烯小球后, 通过扫描电子显微镜观察到周期排列的三角状金纳米颗粒点阵. 通过紫外-可见分光光度计测试所制备样品的光吸收特性, 发现表面等离子体共振峰随粒径增大发生红移, 随金纳米颗粒高度增加发生蓝移. 基于Mie理论, 利用Matlab软件编程对不同粒径的金阵列光吸收特性进行理论模拟, 并与实验结果进行对比. 关键词： 纳米球刻蚀 金纳米颗粒阵列 表面等离子体共振     

Fabrication of large-scale periodic silicon nanopillar arrays for 2D nanomold using modified nanosphere lithography

We present a fabrication procedure that can form large-scale periodic silicon nanopillar arrays for 2D nanomold which determines the feature size of nanoimprint lithography, using modified nanosphere lithography. The size of silicon nanopillars can be easily controlled by an etching and oxidation process. The period and density of nanopillar arrays are determined by the initial diameter of polystyrene (PS) spheres. In our experiment, the smallest nanopillar has a full width half maximum (FWHM) of approximately 50 nm, and the density of silicon pillar is ∼10⁹/cm². Using this approach, it is possible to fabricate 2D nanoimprint lithography mask with 50 nm resolution.     

Morphology control and electron field emission properties of high-ordered Si nanoarrays fabricated by modified nanosphere lithography

High-ordered silicon nanoarrays were prepared using direct nanosphere lithography combined with thermal oxidation. Atomic force microscope (AFM) images of the silicon arrays show that the patterns of polystyrene (PS) template are well transferred to the silicon surface. The size and morphology of the nanoarrays can be controlled effectively by varying the plasma-therm reactive ion etching (RIE) or thermal oxidation parameters. The field emission studies revealed that the typical turn-on field was about 7-8 V/μm with emission current reached 1 μA/cm². It is also found that the field emission current is highly dependent on the morphology of these Si nanoarrays.     

A Method for Preparation of Ordered Porous Silicon Based on a 2D SiO_2 Template

A new method for fabricating ordered porous silicon is reported.A two-dimensional silica nanosphere array is used as a template with a hydrofluoric acid-hydrogen peroxide solution for etching the nanospheres.The initial diameter and distribution of the holes in the resulting porous silicon layer are determined by the size and distribution of the silica nanospheres.The corrosion time can be used to control the depths of the holes.It is found that the presence of a SiO_2 layer,formed by the oxidation of the rough internal surface of the hole,is the primary reason allowing the corrosion to proceed.Ultraviolet reflection and thermal conductivity measurements show that the diameter and distribution of the holes have a great influence on properties of the porous silicon.     

Large-scale protein/antibody patterning with limiting unspecific adsorption

A simple synthetic route based on nanosphere lithography has been developed in order to design a large-scale nanoarray for specific control of protein anchoring. This technique based on two-dimensional (2D) colloidal crystals composed of polystyrene spheres allows the easy and inexpensive fabrication of large arrays (up to several centimeters) by reducing the cost. A silicon wafer coated with a thin adhesion layer of chromium (15 nm) and a layer of gold (50 nm) is used as a substrate. PS spheres are deposited on the gold surface using the floating-transferring technique. The PS spheres were then functionalized with PEG-biotin and the defects by self-assembly monolayer (SAM) PEG to prevent unspecific adsorption. Using epifluorescence microscopy, we show that after immersion of sample on target protein (avidin and anti-avidin) solution, the latter are specifically located on polystyrene spheres. Thus, these results are meaningful for exploration of devices based on a large-scale nanoarray of PS spheres and can be used for detection of target proteins or simply to pattern a surface with specific proteins.     

Fabrication of high-aspect-ratio silicon nanopillar arrays with the conventional reactive ion etching technique

We fabricate silicon nanopillar arrays with pillar diameters smaller than 200 nm by using the conventional reactive ion etching (RIE) technique and nickel masks. We use the ratio between the lateral and vertical etching rates as an estimate of the etching anisotropy. The dependence of this ratio on the rf power, the chamber pressure, and the gas mixture is investigated systematically to achieve the largest etching anisotropy. Using the optimized etching parameters in the RIE process, we demonstrate silicon pillars with smooth surface, vertical sidewalls, and aspect ratios higher than 20. In addition, we employ dilute aqua regia to treat the pillars and shrink the diameters to 70 nm. The pillar height remains ∼2500 nm after the treatment. PACS 52.77.Bn; 81.65.Cf; 85.40.Hp     

Silicon nanotips formed by self-assembled Au nanoparticle mask

The Au nanoparticle monolayer is formed by self-assembly technology on the Si substrates terminated with different functional groups. Silicon nanotips were fabricated by a self-assembled gold colloidal particle monolayer as an etch mask. The silicon nanotips with high density and uniformity in height and shape were obtained using reactive ion etching (RIE). The Si nanotips on the surface of the 3-aminopropyltrimethoxysilane (APTMS)-treated Si substrate are less-ordered array and uniformity than 3-mercaptopropyltrimethoxysilane (MPTMS)-treated Si substrate at the same etching conditions. The ordered array and uniformity of Si nanotips on the APTMS-modified Si substrate was improved through heat-treatment. This result is implied the different functional groups on the Si surfaces could affect the formation of the Si nanostructures during RIE process. The uniformly nanotip pattern with height of >20 nm is obtained on the etched nanoparticle-coated Si substrate. This method can be applied to patterning a wide variety of thin film materials into tip arrays.     

Controlling SERS intensity by tuning the size and height of a silver nanoparticle array

It is demonstrated that the surface-enhanced Raman scattering (SERS) intensity of R6G molecules adsorbed on a Ag nanoparticle array can be controlled by tuning the size and height of the nanoparticles. A firm Ag nanoparticle array was fabricated on glass substrate by using nanosphere lithography (NSL) combined with reactive ion etching (RIE). Different sizes of Ag nanoparticles were fabricated with seed polystyrene nanospheres ranging from 430 nm to 820 nm in diameter. By depositing different thicknesses of Ag film and lifting off nanospheres from the surface of the substrate, the height of the Ag nanoparticles can be tuned. It is observed that the SERS enhancement factor will increase when the size of the Ag nanoparticles decreases and the deposition thickness of the Ag film increases. An enhancement factor as high as 2×10⁶ can be achieved when the size of the polystyrene nanospheres is 430 nm in diameter and the height of the Ag nanoparticles is 96 nm. By using a confocal Raman mapping technique, we also demonstrate that the intensity of Raman scattering is enhanced due to the local surface plasmon resonance (LSPR) occurring in the Ag nanoparticle array.     

Synthesis of PS colloidal crystal templates and ordered ZnO porous thin films by dip-drawing method

Polystyrene spheres (PS) were synthesized by an emulsifier-free emulsion polymerization technique and the PS colloidal crystal templates were assembled orderly on clean glass substrates by dip-drawing method from emulsion of PS. Porous ZnO thin films were prepared by filling the ZnO sol into the spaces among the close-packed PS templates and then annealing to remove the PS templates. The effects of ZnO precursor sol concentration and dipping time in sol on the porous structure of the thin films were studied. The results showed an ordered ZnO porous thin film with designed pore size that depended on the sol concentration and PS size could be obtained. And the shrinkage of pore diameter was about 30-43%. X-ray diffraction (XRD) spectra indicated the thin film was wurtzite structure. The transmittance spectrum showed that optical transmittance decreased with the decrease of wavelength, but kept above 80% optical transmittances beyond the wavelength of 550 nm. Optical band gap of the porous ZnO thin film (fired at 500 °C) was 3.22 eV.     

Growth of size-tunable periodic Ni silicide nanodot arrays on silicon substrates

The fabrications of size-tunable periodic arrays of nickel metal and silicide nanodots on (0 0 1)Si substrates using polystyrene (PS) nanosphere lithography (NSL) and heat treatments have been investigated. The growth of epitaxial NiSi₂ was found to be more favorable for the Ni metal nanodot arrays. The effect becomes more pronounced with a decrease in the size of the Ni nanodots. The sizes of the epitaxial NiSi₂ nanodots were tuned from 38 to 110 nm by varying the diameter of the PS spheres and heat treatment conditions. These epitaxial NiSi₂ nanodots formed on (0 0 1)Si were found to be heavily faceted and the faceted structures were more prone to form at higher temperatures. Based on TEM, HRTEM and SAED analysis, the faceted NiSi₂ nanodots were identified to be inverse pyramids in shape. Compared with the NiSi₂ nanodot arrays formed using single-layer PS sphere masks, the epitaxial NiSi₂ nanodot arrays formed from the double-layer PS sphere templates exhibit larger interparticle spacings and smaller particle sizes. Since the nanoparticle sizes, shapes and interparticle spacings can be adjusted by tuning the diameter of the PS spheres, stacking conditions, and heat treatment conditions, the PS NSL technique promises to be an effective patterning method for growth of other nanostructures.