多孔硅的电化学制备

单晶硅在氢氟酸溶液中阳极氧化可制得多孔硅, 多孔硅是一种以新形态存在的硅, 与单晶硅相比, 它表现出独特的物理性质和化学活性。荧光光谱峰的蓝移表明, 在p-型低掺杂衬底硅上形成的多孔硅中存在量子尺寸效应, 新近获得的Raman光谱也证实了这一点。     

Ag Deposition Forms and Uniformity on Porous Silicon by Electrochemical Method

The electrochemical deposition technique was applied to achieve porous silicon (PS) surface passivated with Ag deposition for improving the properties of PS photoluminescence. The relation of Ag depositing forms to current density and the effect of PS hydrophilic surface on deposition uniformity were investigated. The experimental results indicated that there were two critical current densities (maximum and minimum) in which Ag was absent and electroplated on PS surface correspondingly, and the range of current density for deposition of Ag on porous silicon was from 50 μA/cm² to 400 μA/cm². The process of changing PS surface from hydrophobic into hydrophilic had positive effect on Ag deposition uniformity. Under the same experimental conditions, PS hydrophobic surface presented uneven Ag deposition.However, hydrophilic surface treated with SC-1 solution was even. Finally, the effect of PS surface passivation with Ag even deposition on photoluminescence intensity and stabilization of PS was studied. It was discovered that Ag passivation inhibited the degradation of PL intensity effectively. In addition, excessive Ag deposition had a quenching effect on room-temperature visible photoluminescence of PS.     

光照强度和掺杂浓度对多孔硅形貌和电化学行为的影响

测试分析了光照强度和掺杂浓度对n型硅电极电化学特性的影响。采用电化学阳极腐蚀法在光照辅助下制备多孔硅(PS),通过扫描电镜研究掺杂浓度对PS表面微观形貌的影响,通过积分球测试仪测试研究了PS对光的反射率。结果表明,对于n型硅,光照是激发空穴的必要手段,光照强度越强,硅/电解液界面的电荷转移阻抗越小,更利于反应的进行;掺杂浓度越高,电化学极化阻力越小,促进PS孔密度增加。本实验条件下,形成的PS是微米级孔,随着掺杂浓度的增加,形成的PS孔径越小,孔深存在一个极值;电阻率为0.35Ω·cm的硅片拥有最大的孔深13μm;PS的孔结构大大提升了硅基对光子的捕获能力,相比于单晶硅,在可见-近红外范围,电阻率为0.0047Ω·cm的硅片制备的n-PS对光的反射率已经从30%降低到了5%。     

Electrochemical Impedance Spectroscopic Analysis on the Electrochemical Deposition of Lead Dioxide in Acidic Medium

Electrochemical deposition of pure lead dioxides and modified lead dioxides incorporated with As(V) on a gold electrode was investigated by cyclic voltammetric, in-situ electrochemical impedance spectroscopic, and reflective UV-vis spectroelectrochemical techniques. The focus was given to analyze electrochemical impedance spectroscopic data obtained under various deposition conditions, i.e.,different deposition potentials.     

宏观均相多孔电极电化学阻抗谱基础

电化学阻抗谱可用于诊断多孔电极内电荷转移反应,即界面电荷集聚和电荷传导,以及反应物质输运。本文采用复相量方法,在同态假设条件下,重新推演多孔电极阻抗谱模型,厘清传统多孔电极阻抗谱模型中的模糊性表述。(1) 定义多孔电极表征输入参数,包括电极基体电子电导率σ₁ 、电解质离子电导率σ₂、界面电荷传递电导率g_ct、单位面积界面电容C、固相扩散系数D、速度常数k、电极厚度d、特征孔深L_p 和单位体积表面积S_c;(2) 解析阻抗谱特征输出参数,包括场扩散常数K,特征频率ω₀、ω₁、ω₂、ω₃和 ω_max,它们分别相关于界面传导反应、有限场扩散、氧化还原反应、孔内扩散和最小特征孔尺寸,以及分别对应于从传导到扩散和从扩散到饱和的转折频率f_k1 和f_k2;(3) 当参数X和Z同时变化时(X = σ₁和Z = d,S_c,L_p,C,g_ct,D,k),通过阻抗谱特征参数的演变规律,分析了电荷转移反应中X和Ζ参数耦合竞争;(4)为深入分析电荷转移反应中参数X和Z的耦合竞争,引入了分叉频率f_XZ和f_ZX 。f_XZ和f_ZX所处位置可以用于表征参数X和Z影响电荷转移反应的深度和广度。当分叉频率f_XZ和f_ZX不存在时,表明电荷转移反应中参数X和Z在全频率范围内存在耦合竞争。总之,借助于特征频率和分叉频率,本文一方面研究了动力学参数和微观结构参数对多孔电极中电荷转移反应的影响,另一方面分析谱图的变化及其背后的阻抗谱特征演化规律。本文研究结果可为阻抗谱的系统仿真和辨识提供理论基础,可为多孔电极内电荷转移反应的竞争分析提供技术支撑,还可为电化学储能系统的优化设计提供诊断工具。     

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。     

多孔硅成核的电化学研究

将p型单晶硅在HF溶液中进行阳极电化学腐蚀制备出孔隙率约为30%~85%、直径为2~30nm不等的多孔硅,用原子力显微镜(AFM)观察其表面形貌。采用电化学工作站(CHI660A)监测p型硅电极在不同浓度HF溶液中的电流-电压特性,记录恒电流情况下硅电极的电压变化。这些曲线可从精确反映多孔硅形成的早期成核过程。将这些电化学特性曲线在同一坐标轴下显示,得出多孔硅的电化学成核机理。     

预处理对多孔硅形成过程的影响(英文)

本工作初步探讨了开路电位下对硅片进行预处理时多孔硅的形成过程 .电化学极化实验、扫描电镜和拉曼谱学的研究表明 ,预处理可以加速硅 /溶液界面上的化学或电化学反应 ,从而加快多孔硅的生长过程 ,最终导致光致发光的光谱红移 .多孔硅的厚度随预处理时间的增长而减小     

粉末多孔镍电极电化学阻抗谱及其数学模型

镍电极反应动力学在大多情况下是受固态质子扩散过程控制的，以此为出发点建立了具有明确物理意义的镍电极电化学阻抗谱（EIS）的数学模型．并以该模型为基础，讨论了一些模型参数如双电层电容C（d1）、质子扩散系数D及活性物质位于半径γ0等的改变，电极的不同行电状态以及多孔镍电极中的传质过程对镍电极阻抗谱的影响．理论模型较好地解释了一些实验结果．     

交流阻抗法在细胞分析中应用的研究进展

交流阻抗法作为一种新型的无标记、全程动态、实时分析方法已在细胞研究中得到了广泛应用。本文综述了基于交流阻抗法进行细胞分析的研究新进展,重点对非法拉第阻抗谱法和法拉第阻抗谱法用于细胞分析的原理及应用进行了总结,主要包括交流阻抗法在细胞形态、细胞生长、细胞增殖、细胞凋亡以及作用于细胞的药效和毒性研究中的应用,并对其发展趋势进行了展望。     

尖晶石锂锰氧化物电极首次脱锂过程的EIS研究

研究了尖晶石锂锰氧化物电极首次脱锂过程中的电化学阻抗特征. 通过选取适当的等效电路拟合实验所得的电化学阻抗谱数据, 获得了首次脱锂过程中固体电解质相界面膜(SEI膜)的电阻、电容以及电荷传递电阻、双电层电容等随电极极化电位的变化规律.     

基于原位电化学石英晶体微天平技术的硅基负极粘结剂性能分析

粘结剂是锂离子电池硅基负极材料的重要组成部分,与锂离子电池的性能密切相关.本研究选取两类不同作用机制的典型粘结剂聚偏二氟乙烯(PVDF)和海藻酸钠(ALG),通过原位与非原位结合的方式对不同作用机制的粘结剂对硅电极充放电过程电化学行为的影响进行了初步探讨.首先利用恒电流充放电测试、循环伏安法、交流阻抗法和扫描电子显微镜...     

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.     

Si／C复合材料电极首次嵌锂过程的电化学阻抗谱研究

采用球磨法制备了Si／C复合材料,X射线衍射（XRD）和扫描电子显微镜（SEM）测试结果显示Si／C复合材料中硅保持着良好的晶体结构且均匀的分散于炭黑基体中．充放电测试结果表明Si／C复合材料首次放电容量高达3393mAh／g,4周之后可逆容量均保持在1000mAh／g左右,表现出较好的循环性能．电化学阻抗谱测试结果显...     

Effects of Ultraviolet Illumination and Pre-treatments on Porous Silicon Formation

Although porous silicon is readily formed by anodizing silicon wafers in HF-based solutions, its application in silicon-based optoelectronic devices is greatly limited due to its poor stability and low luminescence yield. It is well recognized that the nature of silicon wafers and the fabrication condition parameters significantly influence uniformity, stability and optical properties of porous silicon. In this work, the ultraviolet illumination and pre-treatments were investigated for porous silicon formation. The surface morphologies and optical properties of the samples were also studied.     

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 .     

两步法制备多孔硅及其表征II：脉冲电流法

采用脉冲阳极／阴极电流和化学氧化两步法分别在1：1的氢氟酸和乙醇溶液中及20％硝酸溶液中制备出孔径约为0．5－3μm,厚度大约为10－20μm的多孔硅样品,将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,与恒电流－化学氧化两步法制得的多孔硅相比,用脉冲电流法得到的多孔硅的孔径范围较大,且多孔层较厚,制备时加紫外光照显著提高了多孔硅的,并发生“蓝移”现象,用脉冲电流法制得的多孔硅在老化后（在干燥器放置一年）同样观察到光致发光明显增强。     

Spontaneous Formation of Microgroove Arrays on the Surface of p‐Type Porous Silicon Induced by a Turing Instability in Electrochemical Dissolution

Self‐organization plays an imperative role in recent materials science. Highly tunable, periodic structures based on dynamic self‐organization at micrometer scales have proven difficult to design, but are desired for the further development of micropatterning. In the present study, we report a microgroove array that spontaneously forms on a p‐type silicon surface during its electrodissolution. Our detailed experimental results suggest that the instability can be classified as Turing instability. The characteristic scale of the Turing‐type pattern is small compared to self‐organized patterns caused by the Turing instabilities reported so far. The mechanism for the miniaturization of self‐organized patterns is strongly related to the semiconducting property of silicon electrodes as well as the dynamics of their surface chemistry.     

Monitoring Electropermeabilization of Adherent Mammalian Cells Through Electrochemical Impedance Spectroscopy

In this work, cell adhesion and electroporation effects have been studied through impedance measurements. Chinese Hamster Ovary (CHO-K1) cells have been plated and grown adherent to multi-electrode arrays and then stimulated to obtain the electroporation. We used Electrochemical Impedance Spectroscopy (EIS) measurements to analyze the impedance variation that occurs with cell adhesion and, consequently, to obtain the intrinsic electrical parameters of the electrode-cell interface through a lumped parameter model. The whole model allows to estimate the correction factor β and the sealing resistance R_seal, both dependent on the cell coverage and adhesion. The electroporation has been performed after cell adhesion, using a custom stimulation bench, able to evaluate the cell-electrode coupling and to stimulate an individually addressable site. By performing EIS measurements, before and after the electroporation, cell status, adhesion and membrane resistance can be detected. From measurements, an impedance decrease as a function of pulse amplitude can be noted. The proposed equivalent electrical model allows to evaluate the variation in membrane conductance due to pores formation. Moreover, average pore radius between 0.5 nm and 2.2 nm, increasing with pulse amplitude, was estimated.     

电沉积Bi2Te3基薄膜的电化学阻抗谱研究

以不锈钢为基底,利用电化学沉积方法制备Bi2Te3基薄膜材料,并采用X射线衍射技术、电子探针微观分析等方法对薄膜进行结构和成分表征,通过电化学阻抗谱技术对不锈钢表面Bi2Te3的电化学沉积机理进行了初步探讨.结果表明Bi-Te和Bi-Te-Se体系具有相似的电化学沉积机理,即Bi3+和2HTeO+或H2SeO3首先被还原为Bi单质和Te或Se单质,然后Bi单质与Te或Se单质反应生成Bi2Te3基化合物,而Bi-Sb-Te体系中,2HTeO+首先被还原为Te单质,生成的Te再与Bi3+和Sb(III)反应生成Bi2Te3基化合物,三种体系的沉积都受电化学极化控制.