电化学阳极氧化条件对阵列多孔硅的影响

采用电化学阳极氧化法,将预光刻图案的p型硅片制备成阵列多孔硅.讨论电化学阳极氧化条件对阵列多孔硅形貌的影响.结果表明:随着HF浓度、电流密度、阳极氧化时间的增大,阵列多孔硅的孔深逐渐加大;当HF:C2H5OH:H2O(体积比)为1:1:1～1:2:5,电流密度为1.56mA/cm2,阳极氧化时间为3h时,制备出的阵列多孔硅具有比较规整的阵列孔,并且孔深能够达到50pm;表面活性剂对阵列孔的形成有很大影响,加入表面活性剂后形成的孔才具有一定的规整性以及深宽比.     

电化学阳极氧化条件对多孔硅及其光催化性能的影响研究

在HF/乙醇电解液中,采用恒电压电化学阳极氧化法,将P型硅片制备成了多孔硅催化剂。以甲基橙模拟废水为目标物,分析了电化学阳极氧化条件对多孔硅光催化甲基橙脱色率的影响。结果表明:随着HF浓度、阳极氧化时间、电流密度和光照时间的增加,甲基橙的脱色率逐渐增大。当V(HF)∶V(乙醇)=1∶1、阳极氧化时间为30min、电流密度为10mA/cm2以及光照时间为60min时,对甲基橙废水的脱色率较好。用十二烷基苯磺酸钠修饰的多孔硅对甲基橙废水有更高的脱色率。同直接催化相比,光催化甲基橙废水的脱色率提高到45.32%。同时对多孔硅表面形貌进行了表征。     

热氧化多孔硅制备及其干涉特性研究

采用电化学阳极氧化法制备彩色薄层多孔硅,经高温热氧化处理后形成稳定的热氧化多孔硅.研究电化学制备条件对热氧化多孔硅的干涉效应和光学厚度的影响,分析热氧化处理前后多孔硅的稳定性.结果表明,在可见光波长范围内,所制备的热氧化多孔硅反射光谱出现一定规律性的干涉条纹,表现出明显的反射干涉现象;随阳极氧化时间、电流密度和HF浓度增大,热氧化多孔硅光学厚度呈增大趋势,当阳极氧化时间为30s、电流密度为520mA/cm2、v(HF):v(C2H5OH)为2:1～5:2时,制备的热氧化多孔硅干涉条纹均匀且光学厚度较大;热氧化处理后,多孔硅结构中的Si-Hx键被Si-O键所取代,其反射干涉特性非常稳定.     

阳极氧化电流密度和时间对多孔硅形貌和电子发射特性的影响

为了应用于场发射显示器,采用电化学阳极氧化,快速热氧化和磁控溅射等方法制备出了金属/多孔硅/硅基底/金属结构的多孔硅电子发射体,并运用扫描电子显微镜观察了多孔硅的微观形貌,结果发现多孔硅的孔径随着电化学阳极氧化电流密度的增加而增加,多孔硅层的厚度随着阳极氧化电流密度和时间乘积的增加而增加。在真空系统中测量了多孔硅的电子发射特性,电子发射的阈值电压Vth随着多孔硅层厚度的增加而增加;最大的发射效率η为7.5‰,此效率出现在孔径6~16 nm,多孔硅层厚度为11.06μm的样品中,对应的器件电压Vps为30V。     

图案化厚膜多孔硅制备与表征

图案化多孔硅是微电子、微机械、光电子器件的重要组成部分.实验以含Si3N4保护层的光刻单晶硅片为基底,采用电化学阳极氧化法制备图案化厚膜多孔硅,分析阳极氧化前后Si3N4保护层表面形貌变化特征和光刻尺寸对图案化多孔硅宽度、膜层厚度的影响规律,表征图案化多孔硅的结构、组成与发光性能.结果表明,氧化前Si3N4保护层局部区域出现枝晶,阳极氧化后形成不均匀孔状结构;制备的图案化多孔硅膜厚62～83μm,其横向扩展程度和膜层厚度均随光刻尺寸增大呈减小趋势;图案化多孔硅微结构含大量不规则裂纹和硅柱,新鲜制备的表面含Si-Hx键,其光致发光峰值波长650nm.     

高度有序多孔阳极氧化铝膜形成机理的探讨

使用高纯铝片,利用电化学阳极氧化制备了多孔阳极氧化铝(AAO)膜,用原子力显微镜(AFM)对其形貌进行了表征,提出铝阳极氧化过程中纳米孔从无序到有序的自组织模型,探讨了高度有序六角形纳米孔阵列的形成过程,并分析了影响纳米孔有序度的因素及提高有序度的途径.根据自组织模型探讨了长时间阳极氧化和二次氧化条件下形成高度有序六角形纳米孔阵列的机理.     

Ti6A14V表面纳米多孔氧化膜的电解制备及形成机理研究

在(NH4)2SO4/NH4F电解液中,采用阶段升压至预定电压,然后恒压阳极氧化在Ti6A14V表面制备出纳米多孔氧化膜.利用SEM、XRD对纳米多孔氧化膜进行表征.研究表明,电解液pH值和外加电压对纳米多孔氧化膜形成和形貌影响非常大.电解液的pH值=4.O,恒压为20V时,形成孔均匀规整的纳米多孔氧化膜,孔内径约为85nm.纳米多孔氧化膜形成机理是:首先钛合金表面钝化,在F-作用下钝化表面发生孔蚀而形成原始胚胎孔,然后胚胎孔处氧化膜在电场支持下发生场致溶解而成大孔.     

甘油对阳极氧化铝纳米孔形成过程的影响

电解电压、电解质种类以及添加剂等因素对氧化铝多孔膜的形成过程有显著影响.在电解液中加入甘油作为添加剂,不但可以增加阳极氧化形成的多孔膜的厚度,而且有利于增强氧化膜的韧性.采用高纯铝作阳极,铂网作为阴极,在草酸溶液中进行恒压阳极氧化.研究了在3%(质量分数)草酸溶液中,添加甘油对氧化铝多孔膜形成过程的影响.结果发现,添加甘油并不会改变氧化铝多孔膜的形成过程,也不会改变形成氧化铝多孔膜中Al2O3的非晶态结构,但甘油的加入将降低阳极氧化时多孔氧化铝膜的生长速度以及氧化铝阻挡层的形成速度,同时增加了纳米孔阻挡层的厚度,因此增加阻挡层的形成时间.在阳极氧化电解液中加入甘油还有利于减小氧化铝多孔膜的纳米孔孔径.     

多孔阳极氧化铝模板制备的研究进展

多孔阳极氧化铝(PAA)模板在制备纳米材料、光谱材料、磁性材料、生物传感材料、太阳能电池材料等领域有着极为广泛的应用。实现多孔阳极氧化铝模板的孔径、孔间距、氧化层厚度等参数的可控制备是获得最佳性能材料的关键。概述了近年来多孔阳极氧化铝模板制备的研究进展,简要介绍了在电化学方法制备条件下各种工艺因素对模板形貌的影响,并综述了利用多孔阳极氧化铝作为模板合成纳米材料的几种方法。     

发光多孔硅的制备及其电化学成膜机制研究

研究了阳极氧化法制备多孔硅的工艺，表面形貌及电化学成膜机制。     

Nanopore gradients on porous aluminum oxide generated by nonuniform anodization of aluminum

A method for surface engineering of structural gradients with nanopore topography using the self-ordering process based on electrochemical anodization of aluminum is described. A distinct anodization condition with an asymmetrically distributed electric field at the electrolyte/aluminum interface is created by nonparallel arrangement between electrodes (tilted by 45°) in an electrochemical cell. The anodic aluminum oxide (AAO) porous surfaces with ordered nanopore structures with gradual and continuous change of pore diameters from 80 to 300 nm across an area of 0.5-1 cm were fabricated by this anodization using two common electrolytes, oxalic acid (0.3 M) and phosphoric acid (0.3 M). The formation of pore gradients of AAO is explained by asymmetric and gradual distribution of the current density and temperature variation generated on the surface of Al during the anodization process. Optical and wetting gradients of prepared pore structures were confirmed by reflective interferometric spectroscopy and contact angle measurements showing the ability of this method to generate porous surfaces with multifunctional gradients (structural, optical, wetting). The study of influence of pore structures on cell growth using the culture of neuroblastoma cells reveals biological relevance of nanopore gradients and the potential to be applied as the platform for spatially controllable cell growth and cell differentiation.     

阳极氧化法制备有序纳米多孔氧化铝膜的研究

利用电化学阳极氧化的方法,在草酸溶液中,精确控制反应条件,在高纯铝片表面有序生长了纳米多孔氧化铝膜。试验中,分别采用一次阳极氧化和二次阳极氧化方法制备氧化铝膜。利用H3PO4溶液浸泡法对氧化铝膜进行扩孔处理。通过扫描电子显微镜对样品进行表征分析。结果发现,二次阳极氧化制备的氧化铝膜的孔洞分布较一次氧化的更为规则有序,并且孔径大小均匀一致。扫描电镜观察显示,氧化铝膜的扩孔过程可以去掉阻碍层,并调节孔径大小,溶去二次氧化后黏附在氧化层表面的一些杂质,从而使氧化铝模板更为规则有序,孔径均一。这种经过二次阳极氧化和扩孔处理得到多孔阳极氧化铝模板的方法简单,成本较低,可以为后续的纳米材料合成提供高质量的合成模板。     

Highly ordered hexagonally arranged nanostructures on silicon through a self-assembled silicon-integrated porous anodic alumina masking layer

A combined process of electrochemical formation of self-assembled porous anodic alumina thin films on a Si substrate and Si etching through the pores was used to fabricate ideally ordered nanostructures on the silicon surface with a long-range, two-dimensional arrangement in a hexagonal close-packed lattice. Pore arrangement in the alumina film was achieved without any pre-patterning of the film surface before anodization. Perfect pattern transfer was achieved by an initial dry etching step, followed by wet or electrochemical etching of Si at the pore bottoms. Anisotropic wet etching using tetramethyl ammonium hydroxide (TMAH) solution resulted in pits in the form of inverted pyramids, while electrochemical etching using a hydrofluoric acid (HF) solution resulted in concave nanopits in the form of semi-spheres. Nanopatterns with lateral size in the range 12-200?nm, depth in the range 50-300?nm and periodicity in the range 30-200?nm were achieved either on large Si areas or on pre-selected confined areas on the Si substrate. The pore size and periodicity were tuned by changing the electrolyte for porous anodic alumina formation and the alumina pore widening time. This parallel large-area nanopatterning technique shows significant potential for use in Si technology and devices.     

The dependence of hydrofluoric acid concentration during anodization on photoluminescence of porous silicon

The mixture of hydrofluoric (HF) acid and ethanol is used as an electrolyte during anodization of silicon. We investigated the effect of the ratio of HF acid to ethanol on photoluminescence. It is concluded that porous silicon anodized with the electrolyte containing 35 or 40% HF acid provides strong photoluminescence. The fact implies the existence of a chemical reaction including ethanol during anodization other than electrochemical reaction.     

The dependence of hydrofluoric acid concentration during anodization on photoluminescence of porous silicon

The mixture of hydrofluoric (HF) acid and ethanol is used as an electrolyte during anodization of silicon. We investigated the effect of the ratio of HF acid to ethanol on photoluminescence. It is concluded that porous silicon anodized with the electrolyte containing 35 or 40% HF acid provides strong photoluminescence. The fact implies the existence of a chemical reaction including ethanol during anodization other than electrochemical reaction.     

Thermal annealing of porous silicon to develop a quasi monocrystalline structure

Low porosity (~20–30%) porous silicon produced by electrochemical anodization was annealed in the temperature range 1000–1150 °C under pure hydrogen atmosphere and under hydrogen mixed with nitrogen in different proportions for a duration of 15–60 min. Porous silicon was transformed to quasi monocrystalline porous silicon (QMPS) in the temperature range 1050–1100 °C under pure hydrogen atmosphere. The crystallinity was confirmed by grazing incidence X-ray diffraction. Field emission scanning electron microscopic (FESEM) studies revealed that the surface layer is pore free with a few voids embedded inside the body. Atomic force microscopic (AFM) studies confirmed relatively smooth and uniform surfaces under the same annealing conditions. Our experimental results concluded that the recrystallization of porous silicon at 1100 °C and in presence of pure hydrogen exhibits lower reflection loss compared to bulk crystalline silicon. Also the electrical resistivity of QMPS makes it suitable for optoelectronic devices and solar cells.     

Single-step direct fabrication of pillar-on-pore hybrid nanostructures in anodizing aluminum for superior superhydrophobic efficiency

Conventional electrochemical anodizing processes of metals such as aluminum typically produce planar and homogeneous nanopore structures. If hydrophobically treated, such 2D planar and interconnected pore structures typically result in lower contact angle and larger contact angle hysteresis than 3D disconnected pillar structures and, hence, exhibit inferior superhydrophobic efficiency. In this study, we demonstrate for the first time that the anodizing parameters can be engineered to design novel pillar-on-pore (POP) hybrid nanostructures directly in a simple one-step fabrication process so that superior surface superhydrophobicity can also be realized effectively from the electrochemical anodization process. On the basis of the characteristic of forming a self-ordered porous morphology in a hexagonal array, the modulation of anodizing voltage and duration enabled the formulation of the hybrid-type nanostructures having controlled pillar morphology on top of a porous layer in both mild and hard anodization modes. The hybrid nanostructures of the anodized metal oxide layer initially enhanced the surface hydrophilicity significantly (i.e., superhydrophilic). However, after a hydrophobic monolayer coating, such hybrid nanostructures then showed superior superhydrophobic nonwetting properties not attainable by the plain nanoporous surfaces produced by conventional anodization conditions. The well-regulated anodization process suggests that electrochemical anodizing can expand its usefulness and efficacy to render various metallic substrates with great superhydrophilicity or -hydrophobicity by directly realizing pillar-like structures on top of a self-ordered nanoporous array through a simple one-step fabrication procedure.     

Absorption enhancement of near infrared in Te doped nanoporous silicon

In this paper, the optical properties of Te doped nanoporous silicon have been studied. The nanoporous silicon was fabricated by using alkaline etching and electrochemical anodization. The etched nanoporous silicon was injected with Te atoms by ion implantation. These nanostructures formed in electrochemical anodization directly affect the optical properties of nanoporous silicon such as reflectance, transmittance and absorptance. According to the optical measurement, the absorptance of the Te doped nanoporous silicon is over 80 % in the wavelength range from 250 to 1,100 nm. The absorptance of Te doped nanoporous silicon at wavelength longer than 1,100 nm is almost four times of that of untreated silicon, indicating that the ion implantation of Te element increases the NIR absorption of nanoporous silicon considerably.