We acknowledge the services of Stanley Flegler, Carol Flegler, and Abigail Tirrell at the MSU Center for Advanced Microscopy. We thank Ray Clark and Mark Wilson for technical assistance with the set-up of the electrochemical etching apparatus. Earlier contributions from Anne Benjamin, Georg Bollen, Rafael Ferrer, David Lincoln, Stefan Schwarz and Adrian Valverde, and technical assistance from John Yurkon are also acknowledged. This work was partially supported by the National Science Foundation contract no. PHY-1102511 and PHY-1307233, Michigan State University and the Facility for Rare Isotope Beams, and Central Michigan University.

1.电化学腐蚀<ol><li> 实验装置 <ol><li> 仪器 注意:电化学蚀刻设置需要一个标准0 - 30伏直流（DC）台式电源和相应的电缆，分液漏斗，一个宽基底玻璃烧杯中，标准杆和效用钳电绝缘夹具。小螺丝，绝缘支座，和鳄鱼夹也将被要求。其他项目，下面描述并且在图1中的蚀刻装置的图所示，必须制造。 <ol><li>从约100毫米长直径6毫米铝棒使钨杆保持器。钻一个0.5mm直径大约为8毫米深的孔中的中心，并进行了螺纹孔为一个4-40螺钉在侧保持杆就位。 </li><li>从约100mm×30毫米x 3毫米厚的铜板制作反电极具有约75毫米×20毫米×1.5毫米深的水库磨成它，并在中心1.5毫米直径的孔。附上大约15毫米长的绝缘支座到反电极的背面。 </li><li>通过钻6毫米直径为8毫米深的孔成大约75×20×20mm的铜块作出的FEP捕手。 </li></ol></li><li> 钨棒的制备 <ol><li>使用断线钳到直径0.5mm钨棒切成大约25毫米的长度。 </li><li>清洁的丙酮棒在15分钟的超声浴。 </li><li>用去离子水冲洗杆。 </li></ol></li><li> 蚀刻液 注意:NaOH溶液是腐蚀性的碱溶液，NFPA 704标签:可燃性（0），健康（3），不稳定性/反应活性（0），特别（COR） - 和可以引起化学灼伤如果它在与皮肤接触或眼睛。油烟吸入可引起刺激和灼伤呼吸道。当处理NaOH溶液，WEA- [R化学防溅护目镜和面罩来保护眼睛，手套，以保护皮肤围裙。在通风橱中进行蚀刻过程或佩戴呼吸器。护理应执行步骤1.1.3.1时以产生稀释的NaOH溶液作出。这个过程是高度放热的，并且可以释放可导致烧伤或点燃易燃，并且可能导致溶液飞溅出容器的热量。 <ol><li>通过重量NaOH溶液370毫升去离子水加入30ml的50％相结合，使的400ml总体积进行的1.5M NaOH溶液。 </li><li>填充该NaOH溶液的分液漏斗。 </li></ol></li><li> 切断电路 注意:如果直流电源是手动操作，那么运营商将关闭电源关闭，一旦钨棒已经蚀刻一路过关斩将（参见1.2.2）。在手工操作的情况下，跳到步骤1.2。对于直流电源自动切断，所示的切断电路（&lt;强&gt;图2和以下描述）时，应构成。在这里，我们实现了使用数据采集卡的计算机控制。 <ol><li>与直流电源串联一个电流表。 </li><li>并联的两个电阻器，R 1和R 2串联和地点与电路的钨棒/反电极的蚀刻腿。 （对于R 1和R 2标称值分别为R 1 = 5kΩ和R 2 = 10千欧）。 </li><li>监视横跨与模拟-数字转换器（ADC）和合适的计算机控制软件，例如 LabVIEW中的电阻器之一的电压。所监视的电压V 纹 ，可与在这两个电阻器，因此电压，经由穿过蚀刻腿，V 蚀刻的电压， （4） <img alt="19式" src="/files/ftp_upload/54030/54030eq19.jpg" /> ， W¯¯这里的电压被R两端1监视。 </li><li>连接的低电阻电阻器，R L = 1Ω，串联在蚀刻电路。使用的ADC的第二通道，记录电阻两端的电压。然后蚀刻电流通过发现我 蚀刻 ≈V L / R L。 （仅约1mA流动扔了电路的监控站。） </li><li>在软件中，创建一个程序，以输出从数字输入/输出通道（DI / O）为5 V TTL信号或者当超过设定值的蚀刻电压升高，或低于设定值的蚀刻电流下降，表明钨棒经历蚀刻一路。这些值依赖于腐蚀电流和NaOH溶液的摩尔浓度被使用，并应与该实验的测试运行来确定。 </li><li> 如图2中所示，安排5伏TTL信号邻笔继电器停止电流。 </li></ol></li></ol></li></ol><img alt="图2" src="/files/ftp_upload/54030/54030fig2.jpg" /> 图2示意图蚀刻的电路。在蚀刻电路的示意图用于提供恒定的DC蚀刻电流。电流是通过监视的低电阻电阻器的电压确定，并且电压是通过使用一个ADC跨越高电阻电阻器监视电压记录。一种计算机程序，监视当前并提供5 V输出信号打开的蚀刻电路一旦低于规定值的电流下降的继电器。 <a href="https://www.jove.com/files/ftp_upload/54030/54030fig2large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <ol start="2"><li> 蚀刻过程 <ol><li> 设备的准备 <ol><li>建立appar的ATU 如图1，用设置在宽基底玻璃烧杯中，并位于其上方的阴极铜内的铜的FEP捕手块，通过绝缘支座间隔开关。 </li><li>设置在DC电源的电流为所需的值，一般为200毫安。 </li><li>放置一个钨棒在支架和鳄鱼夹连接直流电源到4-40夹持螺钉的正极端子。 </li><li>通过在铜阴极的孔插入钨棒，使得约12毫米的钨棒的穿过孔。 </li><li>电源的负极端子连接到与另一个鳄鱼夹在铜阴极。 </li></ol></li><li> 蚀刻 <ol><li>手动调节分液漏斗的滴速通过孔相匹配的滴速，大约每3秒滴注。等待中的阴极铜水库变满。 </li><li>打开直流电源到begin蚀刻。 </li><li>如果在手动模式下操作，关闭直流电源一旦尖端的底部蚀刻一路通过和下降。如果与自动关闭开关操作，蚀刻电流就会被自动切断，一旦杆蚀刻通过。 </li></ol></li></ol></li></ol> 2.场发射点的表征<ol><li> 提示检查 <ol><li>小心地从捕手块用钳子镊子或尖底。松开螺丝4-40，并轻轻拉动上提示出用钳子或钳子取下钨棒持有人上部一角。 </li><li>用丙酮，然后用去离子水冲洗。 </li><li>用光学显微镜检查。提示应该被视为汇聚到细点。那些不这样做， 例如 ，因为它们被弯曲或不具有规则的锥体结构中，应该被丢弃。 图3示出的例子（一）良好的尖端和（b）的弯曲尖端。 </li><li>提示储存在干燥器中。 </li></ol></li></ol><img alt="图3" src="/files/ftp_upload/54030/54030fig3.jpg" /> 图3. FEP提示的光学图像。（ 一 ）一个很好的提示和（b）一个坏的提示，通过光学显微镜观察。图片<a href="https://www.jove.com/files/ftp_upload/54030/54030fig3large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <ol start="2"><li> 扫描电子显微镜（SEM）成像 <ol><li>用于SEM成像，安全FEP提示，以导电夹持器使用导电带或由它们拧到它（ 例如 ， 见图4）和图像中的扫描电镜，根据制造商的在约1,800X和37,000X的放大倍率的协议，以查看的锥尖端和尖端的端部，分别</li></ol></li> &lt;/ OL&gt; <img alt="图4" src="/files/ftp_upload/54030/54030fig4.jpg" /> 图的SEM图像4. FEP持有者。（A）的顶部和的图片（二）用于紧固前置机同时用扫描电镜成像，在支架底部<a href="https://www.jove.com/files/ftp_upload/54030/54030fig4large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图5" src="/files/ftp_upload/54030/54030fig5.jpg" /> 图5.场发射装置。示意图装置用于将高压施加到前置机同时在真空下，以产生电子束。电子束电流法拉第杯具皮安表监控。 <a href="https://www.jove.com/files/ftp_upload/54030/54030fig5large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <ol start="3"><li><stroNG&gt;场发射测试<ol><li> 仪器 注意:对于场发射测试以下，或类似的，设备是必需的:6路6"conflat法兰跨作为一个真空室，3个6"到2¾"conflat法兰零长度适配器，一个SHV（安全在2¾高电压）馈通"conflat法兰，一个BNC馈通在2¾"conflat法兰，在2¾线性馈通"conflat法兰，一个6"conflat法兰窗，6"conflat凸缘坯料休，涡轮真空泵安装到6"conflat凸缘，和一个后备泵（ 例如，涡旋泵）的涡轮，一个高压（HV）电源能够提供高达-5千伏供给需要偏压FEP，和一个皮安计需要监测来自FEP发射并收集在法拉第杯电子流，参见例如，13，在代替法拉第杯的，可以使用一个简单的导电收集板，一个schemati的场致发射建立的c为示出在图5中。 <ol><li>制作第二钨棒持有人（见步骤1.1.1.1）。在支架的另一端与前置机钻一个直径为1毫米的孔钻和挖掘杆侧面的孔4-40螺丝将其固定到SHV引线的真空侧。 </li><li>设置的场致发射装置， 如图5所示。法拉第杯应该从FEP的端部大约2厘米。 </li><li>连接高压供给到该FEP保持器附连到SHV馈通，以及连接皮安计到法拉第杯连接到BNC馈通。 </li><li>抽空的设置多达10个的压力- 6毫巴或更低。 </li></ol></li><li> 场发射 <ol><li>逐步加大对FEP的偏见和显示器上的法拉第杯电子束电流以皮安表。当场发射开始时，一个电流将被观察皮安表。 </li><li>增加在增量步骤（大约50伏特）的HV和记录在每一步皮安计的平均电子束电流。 （如果需要的话，也可以手动完成这一过程可以是计算机控制的例如由LabVIEW程序）。保持低于1μA电子束电流。 </li></ol></li><li>空调<ol><li>通过场发射模式下5 nA的1小时工作状态提示。 </li><li>重复播放当前VS的2.3.2.2 HV扫描。 </li></ol></li></ol></li></ol>

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The authors have nothing to disclose.

我们已经描述了简单的程序，以在一个NaOH溶液电化学蚀刻尖锐场发射点（前置机），并通过场发射模式操作它们来测试前置机。所描述的蚀刻过程是现有技术-薄片下车技术7,8和浮动层技术9,10的变化。但是，我们发现这是更加方便和可靠比上述的方法来实现。 在开始蚀刻过程，以最小化生产具有毛的变形， 例如，一个弯曲的末端，如在图2...

尖锐尖端或点已长期显微镜应用，如场离子显微镜（FIM）1和扫描隧道显微镜（STM）2，和一系列的用于制造各种材料的尖锐尖端技术中使用已开发了3。这些尖头还可以通过施加高电压，以它们作为场致发射点（前置机）动作，并作为一个方便的电子束源。如源的一个应用是通过电子轰击电离（EII）离子的生产。该FEP是在由热发射体产生的温度波动是不期望的应用中是特别有利的。例如，通过背景气体或蒸气的EII离子生产高精度潘宁陷阱4,5。 用于制造前置机一个简单的方法是电化学蚀刻钨棒在氢氧化钠（NaOH）溶液。这种技术相对简单，以便实现具有适度的设备，并已被证明是相当重复，可靠。许多方法在文献中有描述和改进这些技术继续出现6。在这里，我们描述了钨提示在NaOH溶液中电化学腐蚀的方法。我们的方法是片晶落客技术7,8的变化和浮层技术9,10。这两种方法，如它能够生产的从单个蚀刻过程两个尖端。用于蚀刻的尖端的实验装置的图象示于图1。 <img alt="图1" src="/files/ftp_upload/54030/54030fig1.jpg" /> 图1.蚀刻设备。用于钨棒用NaOH溶液的电化学蚀刻的实验装置的照片。 <a href="https://www.jove.com/files/ftp_upload/54030/54030fig1large.jpg" target="_blank">请</a>此处查看该图的放大版本。 在NaOH水溶液碱钨的电化学蚀刻经由一个两阶段过程中发生。首先，中间氧化钨形成​​，并且第二，这些氧化物是非电化学溶解形成可溶性钨阴离子。这个过程的描述，以简化形式，由两个反应 （1）W + 6OH - →WO 3（s）+ 3H 2 O + 6e中- ，和 （2）WO 3（s）+ 2OH - →WO 4 2- + H 2 O 蚀刻电流和所用的NaOH溶液的摩尔浓度影响通过钨棒以蚀刻所需要的时间和电压。在这些效应的研究介绍和讨论。更重要的是，蚀刻参数有场发射模式上的提示的几何形状，并且作为这样的效果，对它们的操作。的几何<html>通过将它们与扫描型电子显微镜（SEM）成像，我们产生的提示进行了表征。这些图像可以被用来估计，例如，尖端半径。此外，该提示是在场致发射模式通过施加通常几百伏的负电压到几千伏给他们，并监测所产生的电子发射电流。场致发射电流之间的关系，I和施加的偏置电压V，可以通过福勒-诺德海姆方程11所描述 （3）I = AV 2ë-Cr EFF / V， 其中r eff是尖的有效半径，A是常数，C是所述第二福勒-诺德海姆恒定<img alt="公式9" src="/files/ftp_upload/54030/54030eq9.jpg" /> ，其中B = 6.83 eV的- 3/2 V /纳米，030eq11.jpg"/&gt;是钨的功函数（ <img alt="11式" src="/files/ftp_upload/54030/54030eq11.jpg" /> ≈4.5电子伏特），k为取决于几何因素（K≈5），和<img alt="12式" src="/files/ftp_upload/54030/54030eq15.jpg" />是诺德海姆图像校正项（ <img alt="12式" src="/files/ftp_upload/54030/54030eq15.jpg" /> ≈1）12。因此，前端的有效半径可以通过测量电子电流作为偏置电压的函数来确定。具体地，它可以从LN的一个所谓的福勒-诺德海姆（FN）情节（I / V 2）与1 / V的斜率来获得。

<table><tbody><tr><td>Tungsten Rod 0.020&quot; x 12&quot;</td><td>ESPI Metals</td><td>&lt;a href=&quot;http://www.espimetals.com/index.php/online-catalog/467-Tungsten&quot;&gt;http://www.espimetals.com/index.php/online-catalog/467-Tungsten&amp;nbsp;&lt;/a&gt;</td><td>3N8 Purity</td></tr><tr><td>50% by weight NaOH solution</td><td>Sigma-Aldrich</td><td>415413-500ML</td><td>500 ml</td></tr><tr><td>Separatory funnel</td><td>Cole-Parmer</td><td>Item#&amp;nbsp;WU-34506-03</td><td>250 ml</td></tr><tr><td>DC Power supply</td><td>BK Precision</td><td>1672</td><td>Triple Output 0 - 32 V, 0 - 3 A DC Power Supply</td></tr><tr><td>Acetone</td><td>Cole-Parmer</td><td>Item#&amp;nbsp;WU-88000-68</td><td>500 ml</td></tr><tr><td>Data Acquisition Card</td><td>National Instruments</td><td>NI PXI-6221</td><td>16 AI, 24 DIO, 2 AO</td></tr><tr><td>Relay</td><td>Magnecraft</td><td>276 XAXH-5D</td><td>7 A, 30 V DC Reed Relay</td></tr><tr><td>6-way 6&quot; conflat flange cross</td><td>Kurt J Lesker</td><td>C6-0600</td><td></td></tr><tr><td>6&quot; to 2-3/4&quot; conflat zero length reducer flange&amp;nbsp; (x3)</td><td>Kurt J Lesker</td><td>RF600X275</td><td></td></tr><tr><td>2-3/4&quot; conflat flange SHV feedthrough</td><td>Kurt J Lesker</td><td>IFTSG041033</td><td></td></tr><tr><td>2-3/4&quot; conflat flange BNC feedthrough</td><td>Kurt J Lesker</td><td>IFTBG042033</td><td></td></tr><tr><td>2-3/4&quot; conflat flange linear feedthrough</td><td>MDC</td><td>660006, REF# BLM-275-2</td><td></td></tr><tr><td>6&quot; conflat flange blankoff</td><td>Kurt J Lesker</td><td>F0600X000N</td><td></td></tr><tr><td>6&quot; conflat flange window</td><td>Kurt J Lesker</td><td>VPZL-600</td><td></td></tr><tr><td>HV Power supply</td><td>Keithley Instruments</td><td>Keithley Model #2290-5</td><td>0 - 5 kV DC HV Power Supply</td></tr><tr><td>Picoammeter</td><td>Keithley Instruments</td><td>Keithley Model #6485</td><td></td></tr><tr><td>Faraday Cup</td><td>Beam Imaging Solutions</td><td>Model FC-1 Faraday Cup</td><td></td></tr></tbody></table>

electrochemical etching and characterization of sharp field emission points for electron impact ionization

A new variation of the drop-off method for fabricating field emission points by electrochemically etching tungsten rods in a NaOH solution is described. The results of studies in which the etching current and the molarity of the NaOH solution used in the etching process were varied are presented. The investigation of the geometry of the tips, by imaging them with a scanning electron microscope, and by operating them in field emission mode is also described. The field emission tips produced are intended to be used as an electron beam source for ion production via electron impact ionization of background gas or vapor in Penning trap mass spectrometry applications.

研究腐蚀参数 在蚀刻工艺期间的电源是恒流模式操作。所需的电压作为钨棒蚀刻掉（由于在杆的阻力的增加），以略微保持这个恒定电流增大。目前几乎降到零当尖端通过蚀刻一路。一个小的电流继续由于流动的事实，上部前端仍然与蚀刻溶液接触。的电流和电压作为蚀刻工艺期间作为时间函数作图示于图...

Watch this Scientific Journal Video about Electrochemical Etching and Characterization of Sharp Field Emission Points for Electron Impact Ionization at JoVE.com

Electrochemical Etching and Characterization of Sharp Field Emission Points for Electron Impact Ionization

A method for electrochemically etching field emission tips is presented. Etching parameters are characterized and the operation of the tips in field emission mode is investigated.

电化学腐蚀和电子碰撞电离夏普场发射点的表征

A new variation of the drop-off method for fabricating field emission points by electrochemically etching tungsten rods in a NaOH solution is described. ...

electrochemical-etching-characterization-sharp-field-emission-points

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9.5K 次观看.  Central Michigan University. A method for electrochemically etching field emission tips is presented. Etching parameters are characterized and the operation of the tips in field emission mode is investigated.

视频: Electrochemical Etching and Characterization of Sharp Field Emission Points for Electron Impact Ionization

Electron Channeling Contrast Imaging for Rapid III-V Heteroepitaxial Characterization

Misfit dislocations in heteroepitaxial layers of GaP grown on Si(001) substrates are characterized through use of electron channeling contrast imaging (ECCI) in a scanning electron microscope (SEM). ECCI allows for imaging of defects and crystallographic features under specific diffraction conditions, similar to that possible via plan-view transmission electron microscopy (PV-TEM). A particular advantage of the ECCI technique is that it requires little to no sample preparation, and indeed can use large area, as-produced samples, making it a considerably higher throughput characterization method than TEM. Similar to TEM, different diffraction conditions can be obtained with ECCI by tilting and rotating the sample in the SEM. This capability enables the selective imaging of specific defects, such as misfit dislocations at the GaP/Si interface, with high contrast levels, which are determined by the standard invisibility criteria. An example application of this technique is described wherein ECCI imaging is used to determine the critical thickness for dislocation nucleation for GaP-on-Si by imaging a range of samples with various GaP epilayer thicknesses. Examples of ECCI micrographs of additional defect types, including threading dislocations and a stacking fault, are provided as demonstration of its broad, TEM-like applicability. Ultimately, the combination of TEM-like capabilities &#8211; high spatial resolution and richness of microstructural data &#8211; with the convenience and speed of SEM, position ECCI as a powerful tool for the rapid characterization of crystalline materials.

The use of electron channeling contrast imaging in a scanning electron microscope to characterize defects in III-V/Si heteroexpitaxial thin films is described. This method yields similar results to plan-view transmission electron microscopy, but in significantly less time due to lack of required sample preparation.

电子通道造影的快速III-V异质特征

Misfit dislocations in heteroepitaxial layers of GaP grown on Si(001) substrates are characterized through use of electron channeling contrast imaging ...

科研

工程学

Atomically Traceable Nanostructure Fabrication

Reducing the scale of etched nanostructures below the 10 nm range eventually will require an atomic scale understanding of the entire fabrication process being used in order to maintain exquisite control over both feature size and feature density. Here, we demonstrate a method for tracking atomically resolved and controlled structures from initial template definition through final nanostructure metrology, opening up a pathway for top-down atomic control over nanofabrication. Hydrogen depassivation lithography is the first step of the nanoscale fabrication process followed by selective atomic layer deposition of up to 2.8 nm of titania to make a nanoscale etch mask. Contrast with the background is shown, indicating different mechanisms for growth on the desired patterns and on the H passivated background. The patterns are then transferred into the bulk using reactive ion etching to form 20 nm tall nanostructures with linewidths down to ~6 nm. To illustrate the limitations of this process, arrays of holes and lines are fabricated. The various nanofabrication process steps are performed at disparate locations, so process integration is discussed. Related issues are discussed including using fiducial marks for finding nanostructures on a macroscopic sample and protecting the chemically reactive patterned Si(100)-H surface against degradation due to atmospheric exposure.

We report a protocol for combining the atomic metrology of the Scanning Tunneling Microscope for surface patterning with selective Atomic Layer Deposition and Reactive Ion Etching. Using a robust process involving numerous atmospheric exposures and transport, 3D nanostructures with atomic metrology are fabricated.

原子纳米结构可追溯制造

Reducing the scale of etched nanostructures below the 10 nm range eventually will require an atomic scale understanding of the entire fabrication process ...

Comprehensive Characterization of Extended Defects in Semiconductor Materials by a Scanning Electron Microscope

Extended defects such as dislocations and grain boundaries have a strong influence on the performance of microelectronic devices and on other applications of semiconductor materials. However, it is still under debate how the defect structure determines the band structure, and therefore, the recombination behavior of electron-hole pairs responsible for the optical and electrical properties of the extended defects. The present paper is a survey of procedures for the spatially resolved investigation of structural and of physical properties of extended defects in semiconductor materials with a scanning electron microscope (SEM). Representative examples are given for crystalline silicon. The luminescence behavior of extended defects can be investigated by cathodoluminescence (CL) measurements. They are particularly valuable because spectrally and spatially resolved information can be obtained simultaneously. For silicon, with an indirect electronic band structure, CL measurements should be carried out at low temperatures down to 5 K due to the low fraction of radiative recombination processes in comparison to non-radiative transitions at room temperature. For the study of the electrical properties of extended defects, the electron beam induced current (EBIC) technique can be applied. The EBIC image reflects the local distribution of defects due to the increased charge-carrier recombination in their vicinity. The procedure for EBIC investigations is described for measurements at room temperature and at low temperatures. Internal strain fields arising from extended defects can be determined quantitatively by cross-correlation electron backscatter diffraction (ccEBSD). This method is challenging because of the necessary preparation of the sample surface and because of the quality of the diffraction patterns which are recorded during the mapping of the sample. The spatial resolution of the three experimental techniques is compared.

The optical, electrical, and structural properties of dislocations and of grain boundaries in semiconductor materials can be determined by experiments performed in a scanning electron microscope. Electron microscopy has been used to investigate cathodoluminescence, electron beam induced current, and diffraction of backscattered electrons.

通过扫描电子显微镜在半导体材料的扩展缺陷的全面表征

Extended defects such as dislocations and grain boundaries have a strong influence on the performance of microelectronic devices and on other applications ...

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and forging. Adoption of this technique is proceeding despite disagreement concerning the underlying mechanism responsible for EAD. The experimental procedure described herein enables a more explicit study compared to previous EAD research by removing thermal effects, which are responsible for disagreement in interpreting previous EAD results. Furthermore, as the procedure described here enables EAD observation in situ and in real time in a transmission electron microscope (TEM), it is superior to existing post-mortem methods that observe EAD effects post-test. Test samples consist of a single crystal copper (SCC) foil having a free-standing tensile test section of nanoscale thickness, fabricated using a combination of laser and ion beam milling. The SCC is mounted to an etched silicon base that provides mechanical support and electrical isolation while serving as a heat sink. Using this geometry, even at high current density (~3,500 A/mm2), the test section experiences a negligible temperature increase (&#60;0.02 &#176;C), thus eliminating Joule heating effects. Monitoring material deformation and identifying the corresponding changes to microstructures, e.g. dislocations, are accomplished by acquiring and analyzing a series of TEM images. Our sample preparation and in situ experiment procedures are robust and versatile as they can be readily utilized to test materials with different microstructures, e.g., single and polycrystalline copper.

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Isolating electrical and thermal effects on electrically assisted deformation (EAD) is very difficult using macroscopic samples. Metallic sample micro- and nanostructures together with a custom test procedure have been developed to evaluate the impact of applied current on the formation without joule heating and evolution of dislocations on these samples.

一种新的方法<em&gt;原位</em&gt;纳米级样品的机电表征

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and ...

Atom Probe Tomography Analysis of Exsolved Mineral Phases

Element diffusion rates and temperature/pressure control a range of fundamental volcanic and metamorphic processes. Such processes are often recorded in lamellae exsolved from host mineral phases. Thus, the analysis of the orientation, size, morphology, composition and spacing of exsolution lamellae is an area of active research in the geosciences. The conventional study of these lamellae has been conducted by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and more recently with focused ion beam (FIB)-based nanotomography, yet with limited chemical information. Here, we explore the use of atom probe tomography (APT) for the nanoscale analysis of ilmenite exsolution lamellae in igneous titanomagnetite from ash deposits erupted from the active Soufri&#232;re Hills Volcano (Montserrat, British West Indies). APT allows the precise calculation of interlamellar spacings (14&#8211;29 &#177; 2 nm) and reveals smooth diffusion profiles with no sharp phase boundaries during the exchange of Fe and Ti/O between the exsolved lamellae and the host crystal. Our results suggest that this novel approach permits nanoscale measurements of lamellae composition and interlamellar spacing that may provide a means to estimate the lava dome temperatures necessary to model extrusion rates and lava dome failure, both of which play a key role in volcanic hazard mitigation efforts.

Analysis of the morphology, composition, and spacing of exsolution lamellae can provide essential information to understand geological processes related to volcanism and metamorphism. We present a novel application of APT for the characterization of such lamellae and compare this approach to the conventional use of electron microscopy and FIB-based nanotomography.

原子探针断层扫描分析的解脱矿物相

Element diffusion rates and temperature/pressure control a range of fundamental volcanic and metamorphic processes. Such processes are often recorded in ...

环境科学

Electrochemical Roughening of Thin-Film Platinum Macro and Microelectrodes

This protocol demonstrates a method for electrochemical roughening of thin-film platinum electrodes without preferential dissolution at grain boundaries of the metal. Using this method, a crack free, thin-film macroelectrode surface with up to 40 times increase in active surface area was obtained. The roughening is easy to do in a standard electrochemical characterization laboratory and incudes the application of voltage pulses followed by extended application of a reductive voltage in a perchloric acid solution. The protocol includes the chemical and electrochemical preparation of both a macroscale (1.2 mm diameter) and microscale (20 &#181;m diameter) platinum disc electrode surface, roughening the electrode surface and characterizing the effects of surface roughening on electrode active surface area. This electrochemical characterization includes cyclic voltammetry and impedance spectroscopy and is demonstrated for both the macroelectrodes and the microelectrodes. Roughening increases electrode active surface area, decreases electrode impedance, increases platinum charge injection limits to those of titanium nitride electrodes of same geometry and improves substrates for adhesion of electrochemically deposited films.

This protocol demonstrates a method for electrochemical roughening of thin-film platinum electrodes without preferential dissolution at grain boundaries. The electrochemical techniques of cyclic voltammetry and impedance spectroscopy are demonstrated to characterize these electrode surfaces.

薄膜铂金宏观和微电极的电化学粗加工

This protocol demonstrates a method for electrochemical roughening of thin-film platinum electrodes without preferential dissolution at grain boundaries ...

化学

Sample Preparation and Experimental Design for In Situ Multi-Beam Transmission Electron Microscopy Irradiation Experiments

There is a need to understand materials exposed to overlapping extreme environments such as high temperature, radiation, or mechanical stress. When these stressors are combined there may be synergistic effects that enable unique microstructural evolution mechanisms to activate. Understanding of these mechanisms is necessary for the input and refinement of predictive models and critical for engineering of next generation materials. The basic physics and underlying mechanisms require advanced tools to be investigated. The in situ ion irradiation transmission electron microscope (I&#179;TEM) is designed to explore these principles.
To quantitatively probe the complex dynamic interactions in materials, careful preparation of samples and consideration of experimental design is required. Particular handling or preparation of samples can easily introduce damage or features that obfuscate the measurements. There is no one correct way to prepare a sample; however, many mistakes can be made. The most common errors and things to consider are highlighted within. The I&#179;TEM has many adjustable variables and a large potential experimental space, therefore it is best to design experiments with a specific scientific question or questions in mind.
Experiments have been performed on large number of sample geometries, material classes, and with many irradiation conditions. The following are a subset of examples that demonstrate unique in situ capabilities utilizing the I3TEM. Au nanoparticles prepared by drop casting have been used to investigate the effects of single ion strikes. Au thin films have been used in studies on the effects of multibeam irradiation on microstructure evolution. Zr films have been exposed to irradiation and mechanical tension to examine creep. Ag nanopillars were subjected to simultaneous high temperature, mechanical compression, and ion irradiation to study irradiation induced creep as well. These results impact fields including: structural materials, nuclear energy, energy storage, catalysis, and microelectronics in space environments.

Sample preparation techniques are outlined with specific considerations for in situ ion irradiation TEM experiments. Ion species, energy, and fluence are discussed with methods for how to select and compute them. Finally, procedures for conducting an experiment are described and accompanied by the representative results.

There is a need to understand materials exposed to overlapping extreme environments such as high temperature, radiation, or mechanical stress. When these ...

3D Depth Profile Reconstruction of Segregated Impurities Using Secondary Ion Mass Spectrometry

The presented protocol combines excellent detection limits (1 ppm to 1 ppb) using secondary ion mass spectrometry (SIMS) with reasonable spatial resolution (~1 &#181;m). Furthermore, it describes how to obtain realistic three-dimensional (3D) distributions of segregated impurities/dopants in solid state materials. Direct 3D depth profile reconstruction is often difficult to achieve due to SIMS-related measurement artifacts. Presented here is a method to identify and solve this challenge. Three major issues are discussed, including the i) nonuniformity of the detector being compensated by flat-field correction; ii) vacuum background contribution (parasitic oxygen counts from residual gases present in the analysis chamber) being estimated and subtracted; and iii)&#160;performance of all steps within a stable timespan of the primary ion source. Wet chemical etching is used to reveal the position and types of dislocation in a material, then the SIMS result is superimposed on images obtained via scanning electron microscopy (SEM). Thus, the position of agglomerated impurities can be related to the position of certain defects. The method is fast and does not require sophisticated sample preparation stage; however, it requires a high-quality, stable ion source, and the entire measurement must be performed quickly to avoid deterioration of the primary beam parameters.

The presented method describes how to identify and solve measurement artifacts related to secondary ion mass spectrometry as well as obtain realistic 3D distributions of impurities/dopants in solid state materials.

使用二次离子质谱法重建分离杂质的 3D 深度剖面

The presented protocol combines excellent detection limits (1 ppm to 1 ppb) using secondary ion mass spectrometry (SIMS) with reasonable spatial ...

Nanoscale Characterization of Liquid-Solid Interfaces by Coupling Cryo-Focused Ion Beam Milling with Scanning Electron Microscopy and Spectroscopy

Physical and chemical processes at solid-liquid interfaces play a crucial role in many natural and technological phenomena, including catalysis, solar energy and fuel generation, and electrochemical energy storage. Nanoscale characterization of such interfaces has recently been achieved using cryogenic electron microscopy, thereby providing a new path to advancing our fundamental understanding of interface processes.
This contribution provides a practical guide to mapping the structure and chemistry of solid-liquid interfaces in materials and devices using an integrated cryogenic electron microscopy approach. In this approach, we pair cryogenic sample preparation which allows stabilization of solid-liquid interfaces with cryogenic focused ion beam (cryo-FIB) milling to create cross-sections through these complex buried structures. Cryogenic scanning electron microscopy (cryo-SEM) techniques performed in a dual-beam FIB/SEM enable direct imaging as well as chemical mapping at the nanoscale. We discuss practical challenges, strategies to overcome them, as well as protocols for obtaining optimal results. While we focus in our discussion on interfaces in energy storage devices, the methods outlined are broadly applicable to a range of fields where solid-liquid interface play a key role.

Cryogenic Focused Ion Beam (FIB) and Scanning Electron Microscopy (SEM) techniques can provide key insights into the chemistry and morphology of intact solid-liquid interfaces. Methods for preparing high quality Energy Dispersive X-ray (EDX) spectroscopic maps of such interfaces are detailed, with a focus on energy storage devices.

通过冷冻聚焦离子束铣削与扫描电子显微镜和光谱学耦合，对液固界面进行纳米级表征

Physical and chemical processes at solid-liquid interfaces play a crucial role in many natural and technological phenomena, including catalysis, solar ...

Quantitative Atomic-Site Analysis of Functional Dopants/Point Defects in Crystalline Materials by Electron-Channeling-Enhanced Microanalysis

A novel elemental and chemical analysis scheme based on electron-channeling phenomena in crystalline materials is introduced, where the incident high-energy electron beam is rocked with the submicrometric pivot point fixed on a specimen. This method enables us to quantitatively derive the site occupancies and site-dependent chemical information of impurities or intentionally doped functional elements in a specimen, using energy-dispersive X-ray spectroscopy and electron energy-loss spectroscopy attached to a scanning transmission electron microscope, which is of significant interest to current materials science, particularly related to nanotechnologies. This scheme is applicable to any combination of elements even when the conventional Rietveld analysis by X-ray or neutron diffraction occasionally fails to provide the desired results because of limited sample sizes and close scattering factors of neighboring elements in the periodic table. In this methodological article, we demonstrate the basic experimental procedure and analysis method of the present beam-rocking microanalysis.

We provide a general outline of quantitative microanalysis methods for estimating the site occupancies of impurities and their chemical states by taking advantage of electron-channeling phenomena under incident electron beam-rocking conditions, which reliably extract information from minority species, light elements, oxygen vacancies, and other point/line/planar defects.

电化学腐蚀和电子碰撞电离夏普场发射点的表征

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