硅在HF溶液中阳极溶解的研究

Uhlir及Turner早在50年代就已发现^[1,2],硅在HF溶液中阳极极化时,阳极电流大于某一特定值硅表面会发生电抛光反应,而低于这个值硅表面则会形成一层不同颜色的多孔硅层.1990年Canham发现多孔硅层在室温下有光致发光现象^[3],受到科学界的高度重视,在世界范围内掀起了研究多孔硅的热潮^[4].众多的研究表明,多孔硅的发光性能与其微孔的多少、大小和分布密切相关.但多孔硅要发展成为可实用的光电子材料,首先必须制备出微孔分布均匀,孔径及孔深可控的多孔硅材料.这就有必要弄清多孔硅的形成机理^[5],了解硅在HF溶液中的溶解过程及机理.为此,本文对不同掺杂浓度不同导电类型的(111)晶面单晶硅在HF溶液中的电流-电压(I-V)、电容-电压(C-V)特性进行了研究,并对这些特性进行了分析.     

金属离子在多孔硅表面和吸附与电镀过程中金属在多孔硅表面的淀积

刚制备的多孔硅与金属盐溶液接触会产生金属离子在多孔硅表面和吸附现象。实验显示这一现象只发生在新鲜的多孔硅表面, 而存放一月以后的样品不具备此性质。文中把这一现象归因于新鲜的多孔硅表面电子的富集, 溶液中金属离子从多孔硅表面获得电子而附着。多孔硅表面电镀金属过程中, 一定电压下电镀电流密度在起始阶段逐渐下降, 可以用一个指数关系式较好地描述, 在本文中有一个唯象模型予以解释。     

金属离子在多孔硅表面和吸附与电镀过程中金属在多孔硅表面的淀积

刚制备的多孔硅与金属盐溶液接触会产生金属离子在多孔硅表面和吸附现象。实验显示这一现象只发生在新鲜的多孔硅表面, 而存放一月以后的样品不具备此性质。文中把这一现象归因于新鲜的多孔硅表面电子的富集, 溶液中金属离子从多孔硅表面获得电子而附着。多孔硅表面电镀金属过程中, 一定电压下电镀电流密度在起始阶段逐渐下降, 可以用一个指数关系式较好地描述, 在本文中有一个唯象模型予以解释。     

多孔硅镶嵌正丁胺/激光染料复合膜的荧光谱

多孔介质染料镶嵌膜有可能是发展固体染料激光器的一种途径[1].由于其所具有的微孔结构和大的比表面积,故使其成为激光染料理想的载体,以形成多孔硅基发光材料[2].　　我们用正丁胺作碳源,采用射频辉光(ＲＦ)放电法制备碳膜.利用正丁胺、Ｒ6Ｇ/聚乙二醇分别作碳源和蒸发源得到一种混合膜,如将其沉积在刚制备的新鲜多孔硅上则得到多孔硅镶嵌复合膜.本文着重研究了镶嵌于多孔硅中的正丁胺/Ｒ6Ｇ的荧光光谱,并考察了多孔硅衬底的改变对多孔硅镶嵌膜发光的影响.1　样品制备　　(1)多孔硅的制备　制备多孔硅(ＰＳ)所用的材料为(100)晶向的ｐ型单…     

量子限制效应对多孔硅液相电致发光的影响

着重研究多孔硅在阴极偏压下过硫酸铵溶液中电压调制的电致发光现象 .随阴极偏压的增大 ,电致荧光峰位蓝移 ,荧光强度增大 ,同时发现定电压下 ,发生电致发光随时间的衰减伴随着光谱的红移现象 .通过红外光谱、AFM及电化学等手段对电致发光的电位调制机理及荧光衰减机制进行了研究 ,结果表明电致发光与光致发光具有相同的起源 ,电压选择激发不同粒径的多孔硅 ,而导致了发光峰值能量的电位选择性 .在电致发光过程中 ,强氧化剂向多孔硅注入空穴使其表面氧化导致小粒径的硅晶逐渐被剥落 ,使光谱高能部分首先衰减出现了随时间的电致发光红移现象 .这些结果支持量子限制效应在多孔硅液相电致发光中起着重要作用     

疏水多孔硅制备及其对水中有机污染物的吸附

以硅酸钠为硅源,盐酸为催化剂,三甲基氯硅烷(TMCS)为表面改性剂,经溶胶-凝胶和表面改性过程制备出一种疏水性多孔硅材料.采用傅里叶变换红外(FTIR)光谱仪、接触角分析仪、氮气物理吸附仪和扫描电子显微镜(SEM)对其结构和性质进行表征.结果表明:所制备的多孔硅具有分等级孔道结构(中孔-大孔),比表面积为566m2·g-1,孔体积高达2.28cm3·g-1,多孔硅与水的接触角为156°,显示出超疏水特征.对甲苯、汽油、柴油和润滑油的吸附量均可高达自身质量的14倍,丰富的孔道使其在几分钟内即可达到饱和吸附.这种多孔硅在汽油/水混合体系中对汽油具有较高的选择性,同时具有良好的再生能力.经正己烷萃取再生后,多孔硅仍能基本保持初始吸附容量.此方法制备的多孔硅材料在吸附分离污水中的有机物和溢油处理方面具有很好的应用前景.     

多孔硅薄膜上铜微晶的形成

以氯化铜水溶液作电解液,在发光多孔硅薄膜表面上电沉积铜.SEM观测和计算机图像处理结果表明:电沉积之后,在多孔硅薄膜上形成了一些或实心或中空的等边三角形铜微晶,沉积后的多孔硅薄膜的分形维数从2.608降为2.252,其表面由粗糙变为光滑.与物理方法制作相比,这是一种机械强度和导电性能都更加良好的多孔硅薄膜.     

掺稀土多孔硅中稀土光学活化的新方法: 微波热法

首次报道掺稀土多孔硅中稀土光学活化的一种新方法--微波热法.经微波加热处理后,掺稀土多孔硅样品外观均匀;室温下,分别观察到掺铒多孔硅在-1.5μm处、掺钕多孔硅在-1.06μm处强的光致发光.除起加热作用外,微波与样品之间的非热相互作用在稀土的光学活化方面与也起重要作用.     

多孔硅/硝酸钆复合材料制备与表征

多孔硅/硝酸钆复合材料因具有爆炸能量高和环境危害小等特点而受到世界各国广泛关注.采用电化学阳极氧化法制备新鲜多孔硅并滴加硝酸钆形成复合材料,表征其化学组成与结构.结果表明,当电解液HF与EtOH体积比为1∶1、电流密度为50mA·cm-2、阳极氧化时间为30min时,形成的多孔硅孔隙率较大,适宜与硝酸钆形成复合材料;与新鲜多孔硅相比,滴加硝酸钆乙醇溶液的多孔硅在1675、1534、1382和1217cm-1出现了4个新的吸收峰,结合N1s和Si2p结合能有明显化学位移的现象,表明硝酸钆乙醇溶液与多孔硅之间存在相互作用,结构中有-NH2形成,表面Si-Hx键被氧化为si-O键;当电火花触发时,观察到多孔硅/硝酸钆复合材料爆炸现象.     

酸浸蚀Al-Si合金制备锂离子电池高性能多孔硅负极材料

本文首次提出利用酸浸蚀Si-Al（含Al 80%）合金粉末的方法制备多孔硅材料. 分析表明制得的多孔硅材料为晶体,并具有由纳米颗粒结集成的海绵状多孔结构,其粒径约20 μm,比表面102.7 m²·g^-1. 多孔硅电极按多孔硅:导电碳:粘结剂 = 1:1:1（by mass）涂成. 在添加15%氟化碳酸乙烯酯（FEC）的1 mol·L^-1 LiPF₆/EC + DMC（1:1,by volume）电解液,在100 mA·g^-1电流密度充放电,多孔硅电极的首次放电比容量2072 mAh·g^-1 Si. 经237次充放电循环后,其放电容量仍可保持在1431 mAh·g^-1 Si,显示了相当高的充放电稳定性. 这归因于其海绵状多孔结构有足够的微空间以承受充电过程中硅的急剧膨胀. 硅微粒的纳米尺寸有利于锂在Li-Si合金中的扩散. 纳米硅微粒可牢固地联成一整体,不易因膨胀、收缩而粉化断裂. 这种构筑多孔硅负极材料的新方法操作简便、成本低廉,有着很好的应用前景.     

两步法制备多孔硅及其表征I:恒电流法(英文)

本工作通过采用电化学极 -化学氧化两步法在 1:1氢氟酸和乙醇溶液中制备出孔径约为 1～ 2 μm ,厚度大经为 6～ 10 μm的多孔硅样品 .首先将 0 .0 3A/cm2 的恒电流施加到p( 10 0 )硅片一段时间 ,然后将该硅片浸到 2 0 %的硝酸溶液中氧化一段时间 .通过此方法获得的多孔硅结构再进一步用扫描电子显微镜和拉曼光谱仪进行表面形貌和光学性质的考察 .所有制备出的多孔硅结构均有光致发光现象 .老化的多孔硅样品 (在干燥器放置一年 )的光致发光谱峰强度明显增强 ,但分别经过苯乙烯和十六碳烯 ( 1)两种有机溶剂处理 1h后的老化多孔硅样品的光致发光强度却没有显著改变 .     

Self-assembled Alkylation of Atomically Flat Hydrogen-terminated Silicon (111) Surface By Using Highly Polarized Fluoroalkylsilane

Hydrogen-terminated silicon surface is of technological importance to semiconductor processes such as pre-gate^[1]. Re-contamination and re-oxidation on silicon surface become more stringent issues in order to meet the requirements in the process for producing reduced size IC chips. The modification of silicon surfaces by various strategies has attracted more attention in the past few years^[2-4]. The frequently used techniques to attach functional groups to silicon surfaces are via chemical^[2], photochemical^[3] and electrochemical reactions^[4]. Various ways to attach monlayers to silicon surfaces has been reported, including alkylation of silicon with alkenes, alkyenes, aldehydes, alcohols and Grigard reagents under photoactivated or catalytic reactions. Particularly, porous silicon prepared by chemical or electrochemical treatments has been extensively studied. Preparation of passivated layers on porous silicon surfaces has disadvantages that the silicon surfaces are damaged by reactive agents during the reaction or become porous for attachment of molecules. Recently, self-assembled monolayer of alcohols on porous silicon was reported at modest heating without the aid of catalyst or photoexcitation or potential^[5]. In the paper, we report a novel method to attach highly polarized fluoroalkylsilane on atomically flat Si(111) surface at room temperature and to form a self-assembled monolayer to prevent the silicon surface from re-contamination and re-oxidation.     

发光多孔硅的光谱及电化学研究

单晶硅是E_g为1.1eV的间接带隙半导体材料,在可见光区不发光,不能应用于光电子领域.但是,Canham 1990年首次发现^[1],适当条件下形成的多孔硅在室温下就可发出强度能与Ⅲ-Ⅴ族半导体发光二极管相媲美的可见光。     

Visible-laser desorption/ionization on gold nanostructures

In this report, we describe the visible-laser desorption/ionization of biomolecules deposited on gold-coated porous silicon and gold nanorod arrays. The porous silicon made by electrochemical etching was coated with gold using argon ion sputtering. The gold nanorod arrays were fabricated by electrodepositing gold onto a porous alumina template, and the subsequent partial removal of the alumina template. A frequency-doubled/tripled Nd : YAG laser was used to irradiate the gold nanostructured substrate, and the desorbed molecular ions were mass-analyzed by a time-of-flight mass spectrometer. The desorption/ionization of biomolecules for both substrates was favored by the use of the 532-nm visible-laser, which is in the range of the localized surface plasmon resonance of the gold nanostructure. The present technique offers a potential analytical method for low-molecular-weight analytes that are rather difficult to handle in the conventional matrix-assisted laser desorption/ionization (MALDI) mass spectrometry.     

脉冲阳极氧化条件对多孔硅法布里-珀罗干涉特性影响

采用电化学脉冲阳极氧化法制备具有干涉效应的多孔硅. 研究电流密度、有效阳极氧化时间、电解液组成对多孔硅法布里-珀罗(F-P)干涉特性的影响, 利用光纤光谱仪测量多孔硅反射光谱并计算其光学厚度. 结果表明, 当阳极氧化电流密度78 mA•cm－2、有效阳极氧化时间5 min、氢氟酸与乙醇体积比VHF∶VEtOH＝2∶1时, 制备的多孔硅法布里-珀罗干涉条纹均匀, 膜层性质稳定; 当与饱和乙醇气体接触时, 多孔硅反射光谱吸收峰位由612红移到637 nm, 光学厚度由5864增加到6296 nm, 表明利用多孔硅法布里-珀罗干涉效应检测乙醇气体思路是可行的.     

多孔与平面硅电极界面的电化学行为

研究了重掺杂n-型单晶硅(CSi)在氢氟酸体系中生成多孔硅(PSi)的电化学行为,根据线性极化曲线,选取不同的电流密度,采用恒电流阳极极化法,制备了一系列多孔硅层。利用扫描电子显微镜对其进行了表面和断面形貌的表征,通过线性扫描极化技术和计时电位法,比较了单晶硅电极和多孔硅电极的电化学行为,分析了多孔硅形成前后的塔菲尔曲线和计时电位曲线,给出了多孔硅形成过程中的重要电化学参数,如腐蚀电流、开路电位、塔菲尔斜率等。并对其进行深入分析,根据实验结果,提出了单晶硅电极/电解质界面和多孔硅电极/电解质界面的结构模型,并利用该模型讨论了两种电极界面的电化学特性。     

Bismuth Nanoparticles@Porous Silicon Nanostructure,Application as a Selective and Sensitive Electrochemical Sensor for the Determination of Thioridazine

A bismuth@porous silicon (Bi/PSi) nanostructure is fabricated and used as a new highly sensitive electrochemical sensor for measurement of thioridazine. For this purpose, commercial silicon powder is converted to porous silicon using metal‐assisted chemical etching method. Then, bismuth nanoparticles are deposited on the surface of the porous silicon that synthesized in the previous step. The effects of pH and instrumental parameters are studied on the sensor response. After optimization of the parameters, differential pulse voltammetry is used to determine sub‐micro molar amounts of thioridazine. The Linear region of the electrochemical sensor is in the range of 0.1 to 260 μmol L⁻¹ thioridazine with a detection limit of 0.03 μmol L⁻¹, when Bi/PSi/CNTPE is used as an electrochemical sensor. The precision and accuracy of the sensor is evaluated. The Bi/PSi/CNTPE is used as an appropriated tool for accurate measurement of low amounts of thioridazine in real samples with satisfactory results.     

Impact sensitivity of energy systems based on nanoporous silicon and oxidant: influence of the hydrogen content and specific surface

The impact sensitivity of the energy systems based on nanoporous silicon, obtained by electrochemical etching of monocrystalline silicon wafers in an HF-containing electrolyte, and calcium perchlorate was studied using a modified Weller—Ventselberg technique (estimation of the impact sensitivity of initiating explosives). The impact sensitivity of these systems is shown to be determined by both the presence of hydrogen, which is stored on the porous silicon surface during the preparation of the latter, and also the influence of other factors, including the specific surface of porous silicon. The composition, amount of the generated gas, and gas evolution rate during nonisothermal and isothermal calcination of porous silicon in a temperature range of 60—120 °С were determined using methods of thermal gravimetry (TG), measurement of the gas volume, and mass spectrometry. The generated gas almost completely consists of hydrogen, and its content in the studied samples of porous silicon achieved ~3.8 wt.%. The calculated activation energy of the hydrogen evolution process in vacuo was 103.7±3.3 kJ mol^–1. The dependences of the impact sensitivity of the energy composition based on porous silicon and heat of combustion of porous silicon on oxygen on the hydrogen content were established. The impact sensitivity of the energy system decreases with a decrease in the hydrogen content in porous silicon and its specific surface.     

阳极氧化与超临界干燥结合制备多孔硅

多孔硅（PS）在室温下发射强可见光，这一发现在国际上引起极大关注，成为材料科学、半导体物理和化学以及信息科学领域研究的热点［1，2］．最近三、四年，国内外对PS制备工艺、影响PS发光的因素、PS发光机制、PS应用前景等方面进行了广泛的研究［2］，但有一些基本问题仍待解决，如关于PS发光机制尚存在分歧；PS电致发光效率低，离应用差距甚远；高多孔度PS微孔结构不稳定等．PS微孔内溶剂蒸发过程中，由于毛细管张力的存在，造成微孔骨架受力不匀．强的应力使PS骨架脆弱，甚至微孔结构坍缩，从而导致PS结构不稳定．对于高多孔度…