扫描隧道探针的制备研究

本文概述针尖对扫描隧道显微镜的重要性,总结制备探针的各种技术,并着重介绍电化学腐蚀制备钨和铂铱合金探针的原理及电路设计。     

扫描隧道显微镜在电化学研究中的改进及应用

扫描隧道显微镜 (STM )在电化学领域有广泛应用。但由于STM是通过感应非常微弱的隧穿电流来反映表面状况 ,而隧穿效应是在一定条件下才能发生的量子效应 ,所以在实际应用中受到不少限制。针对STM在电化学研究中的局限性 ,国内外作了许多改进 ,出现了一些新的装置 ,如电化学扫描隧道显微镜、电化学原子力显微镜、扫描电化学显微镜等。本文介绍STM在电化学研究中的改进及其应用 ,并就发展趋势作简短讨论     

亚微米级毛细管微探针的制作及其应用

设计了一种用热拉伸法制备毛细管微探针的新装置,可制作尖端内外径从亚微米量级至数十微米量级的毛细管微探针。介绍了微探针在细胞人工授精操作中的应用实例,并提出一种基于扫描隧道显微术与电化学技术,利用微探针进行集成电路微细加工的新方法。     

微米尺度线电极的电化学腐蚀法制备

微细电化学线切割加工是最近出现的一种微细加工新方法。本文基于电化学腐蚀原理,制备微细电化学线切割加工中使用的微米尺度线电极。建立了腐蚀过程理论模型,通过测量线电极的电阻变化来实时监测线电极腐蚀过程中的直径大小,并基于虚拟仪器技术建立了线电极制备监控系统。通过试验对钨线电极的腐蚀过程进行分析,得出监控系统的直径计算值与实际值误差低于10%。最后,利用此方法制备出直径5μm的钨线电极。     

电化学两步处理对精磨YG6硬质合金性能及金刚石涂层的影响

采用电化学两步腐蚀法进行表面预处理研究,探讨了电化学腐蚀中电流类型、腐蚀时间等参数对精磨YG6硬质合金基体的影响;在此基体上,采用直流弧光放电等离子体CVD法制备了金刚石薄膜,并采用SEM、激光拉曼光谱仪、原子吸收分光光度计、电动轮廓仪、洛氏硬度计等进行了表征.结果表明:直、交电化学腐蚀都可以有效地去除YG6硬质合金基...     

基于电化学研磨的SPM钨探针制备方法研究

钨探针是扫描隧道显微镜(STM)常用探针之一。为了将钨探针应用于扫描探针显微镜(SPM)，根据钨探针的受力，通过理论分析确定了钨探针的理想轮廓：钨探针的直径变化应具有指数曲线。为了获得指数曲线轮廓、尖锐测头等良好特性的钨探针，分别提出并研究了改进的钨探针液面直流电化学研磨法和薄膜直流电化学研磨法。通过这两种电化学研磨法获得的探针以及通过传统的交流电化学研磨法获得的钨探针，分别在探针的形状、探针尖端曲率半径、表面质量、研磨速度、可复现性等多个方面进行了观察和比较。通过实验发现，除了研磨速度外，改进的液面直流电化学研磨法和薄膜直流电化学研磨法在其他各方面都优于交流电化学研磨法。     

电化学腐蚀法制备微细群圆柱

提出了微细群圆柱结构电化学腐蚀加工法及其形状和尺寸控制方式。根据电化学腐蚀基本原理,通过有限元分析计算群圆柱电化学腐蚀加工过程中的电场分布,优化设计阴极形状。开展了电化学腐蚀法制备微细群圆柱结构的工艺试验,获得了良好的试验结果。     

新型电化学原子力显微镜的研制

电化学原子力显微镜将电化学分析技术与原子力显微镜结合起来,能对生物传感器,新型电池和电腐蚀进行原位电化学扫描探针显微测量分析。为了实现电化学与扫描探针功能的系统集成,在控制电路设计中采用现场可编程门阵列,提高了系统的可靠性。电化学控制箱与原子力显微镜的头部紧密集成,保证微弱信号不受干扰,并具有多种电化学工作模式。系统具有稳定性好,重复性高,抗干扰能力强等优点。     

炼油厂电脱盐换热器腐蚀失效分析

通过对某炼厂焦化装置电脱盐换热器的腐蚀形貌检测、腐蚀产物化学成分分析、电脱盐水质分析,结合生产工艺对换热器的腐蚀原因进行了探讨.结果表明:壳程腐蚀是由于新鲜水中含有的钙、钡及泥沙聚集在换热器壳程表面而导致垢下腐蚀和小阳极-大阴极电化学腐蚀;管程腐蚀是由于电脱盐水的pH值过低造成的析氢电化学腐蚀.     

Cu-Zn合金去合金化法制备纳米多孔铜研究

采用感应熔炼、均匀化处理和电火花线切割及轧制工艺制备Zn含量(原子分数,at%)为25%的Cu-Zn合金前驱体,然后通过化学腐蚀和电化学恒压腐蚀去合金化得到纳米多孔铜材料。研究不同退火温度、化学腐蚀和电化学腐蚀时间对多孔铜孔隙率及形貌和尺寸的影响。结果表明:经800℃均匀化退火后制备的纳米多孔铜的孔隙分布比较均匀,孔隙率较高,且纳米铜的孔径尺寸主要在100nm~200nm之间;当腐蚀电压为5V,腐蚀时间在10min~15min时电化学恒压腐蚀去合金化速度快获得的纳米多孔铜的效果好。     

Reproducible tip fabrication and cleaning for UHV STM

Several technical modifications related to the fabrication and ultra-high vacuum (UHV) treatments of the scanning tunneling microscope (STM) tips have been implemented to improve a reliability of the tip preparation for high-resolution STM. Widely used electrochemical etching drop-off technique has been further refined to enable a reproducible fabrication of the tips with a radius 相似文献   

Two-step controllable electrochemical etching of tungsten scanning probe microscopy tips

Dynamic electrochemical etching technique is optimized to produce tungsten tips with controllable shape and radius of curvature of less than 10 nm. Nascent features such as "dynamic electrochemical etching" and reverse biasing after "drop-off" are utilized, and "two-step dynamic electrochemical etching" is introduced to produce extremely sharp tips with controllable aspect ratio. Electronic current shut-off time for conventional dc "drop-off" technique is reduced to ～36 ns using high speed analog electronics. Undesirable variability in tip shape, which is innate to static dc electrochemical etching, is mitigated with novel "dynamic electrochemical etching." Overall, we present a facile and robust approach, whereby using a novel etchant level adjustment mechanism, 30° variability in cone angle and 1.5 mm controllability in cone length were achieved, while routinely producing ultra-sharp probes.     

Effects of process parameters on the electrochemical etching of sharp metallic tips with an attached mass

The electrochemical etching of a metal wire with an attached mass at the end of the immersed wire is a new technique to enhance the yield rate of sharp tips. Unlike conventional electrochemical etching, the yield rate of sharp tips with subhundred nanometer apex could be increased up to around 60% with the attached mass method. In this article, the effects of the magnitude of attached mass and the taping material used for attachment on the yield rate and tip shape are investigated. Also, the variation of tip shape with respect to the temporal shape of applied electric field, constant or pulsed dc, is examined.     

STM/SEM correlative study of facetted gold

We have integrated an STM unit with a conventional scanning electron microscope in order to perform STM–SEM correlative microscopy. The method is applied to an electrochemically facetted gold sample, which provides a surface structure suitable for this study. We discuss the factors which are relevant in order to obtain a quantitative resolution of the topographic surface structure, by taking advantage of the performances of both techniques. In particular we suggest the use of the STM height distribution as the best parameter for STM/SEM correlation. Finally, from the STM data we deduce that the main process during electrochemical etching is the formation of (111) faces.     

Single-step electrochemical method for producing very sharp Au scanning tunneling microscopy tips

A single-step electrochemical method for making sharp gold scanning tunneling microscopy tips is described. 3.0M NaCl in 1% perchloric acid is compared to several previously reported etchants. The addition of perchloric acid to sodium chloride solutions drastically shortens etching times and is shown by transmission electron microscopy to produce very sharp tips with a mean radius of curvature of 15 nm.     

Preparation of STM tips for in-situ characterization of electrode surfaces

The total current between the tip and the sample in a scanning tunnelling microscopy study of a solid/liquid interface can be dominated by Faradaic charge transfer currents. In such a situation, feedback control of the tunnelling gap, and imaging, is precluded. In this contribution we describe the preparation of glass and polymer coated STM tips that possess < 100 Ų of exposed metal. These tips effectively discriminate against Faradaic current and enable STM imaging in the presence of reversible electroactive solution species at appreciable tip/sample biases.     

Note: Production of sharp gold tips with high surface quality

We present a simple method to produce sharp gold tips with excellent surface quality based on electrochemical etching with potassium chloride. Radii of curvature lie in the range of 20-40 nm and the surface roughness is measured to less than 0.8?nm. The tips are well suited for field emission, field ion microscopy, and likely for tip-enhanced Raman scattering as well as tip-enhanced near-field imaging.     

A combined ion-sputtering and electron-beam annealing device for the in vacuo postpreparation of scanning probes

We describe the setup, characteristics, and application of an in vacuo ion-sputtering and electron-beam annealing device for the postpreparation of scanning probes (e.g., scanning tunneling microscopy (STM) tips) under ultrahigh vacuum (UHV) conditions. The proposed device facilitates the straightforward implementation of a common two-step cleaning procedure, where the first step consists of ion-sputtering, while the second step heals out sputtering-induced defects by thermal annealing. In contrast to the standard way, no dedicated external ion-sputtering gun is required with the proposed device. The performance of the described device is demonstrated by SEM micrographs and energy dispersive x-ray characterization of electrochemically etched tungsten tips prior and after postprocessing.     

Note: electrochemical etching of sharp iridium tips

We describe an etching procedure for the production of sharp iridium tips with apex radii of 15-70 nm, as determined by scanning electron microscopy, field ion microscopy, and field emission measurements. A coarse electrochemical etch followed by zone electropolishing is performed in a relatively harmless calcium chloride solution with high success rate.