Name: precision milling of carbon nanotube forests using low pressure scanning electron microscopy
Uploaded: 2017-02-05T15:00:00.000+00:00
Duration: 8 min 10 s
Description: Watch this Scientific Journal Video about Precision Milling of Carbon Nanotube Forests Using Low Pressure Scanning Electron Microscopy at JoVE.com

This work was supported by the Air Force Office of Scientific Research grant FA9550-16-1-0011 and University of Missouri startup funds. The authors would like to thank the University of Missouri Electron Microscopy Core facility for assistance with SEM imaging and use of patterning equipment and software.

1. CNT样品森林铣削的制备<ol><li> CNT合成 <ol><li>使用原子层沉积13或其它物理气相沉积法的热氧化的硅晶片上沉积氧化铝（矾土）的10纳米。 </li><li>存款通过溅射14或其他物理蒸镀法铁氧化铝载体层上的1纳米。 </li><li>合成使用已建立的方法，如热化学气相沉积15的碳纳米管。 <ol><li>加热20毫米直径的管式炉中，以750℃在400标准立方厘米（sccm）的流动氦和100sccm的氢。引入100sccm的乙烯作为烃类原料气体为约50μm/ min的生长速率。 </li></ol></li></ol></li><li> SEM准备 <ol><li>应用碳纤维带，以一个标准的"直径1/2 SEM存根。如果倾斜的舞台我š需要，重叠在短截线的边缘被研磨的碳纳米管林样品的区域。如果软件控制的电子束光栅扫描将研磨过程中使用，固定CNT系试样的电子束光刻装入以类似的方式。 </li><li>如果铣削所述CNT的横截面，固定存根45°存根保持器与一组螺钉。 </li><li>从ESEM控制软件选择"发泄"图标放空ESEM。 </li><li>打开ESEM舞台门口，存根用一组螺丝固定到SEM阶段。 </li><li>关闭扫描电镜室，并在ESEM控制软件选择"高真空"。 </li><li>虽然扫描电镜室抽，选择使用控制软件中的光束控制选项卡中的3.0 5千伏和光斑尺寸的电子束参数。 </li><li>通过选择探测器选择二次电子检测仪| ETD（SE）在ESEM控制软件。 </li><li>选择在控制软件中的"梁开"图标。光束只能一次室真空小于10 -4乇被激活。使用手动对焦SEM控制旋钮聚焦样本。 </li><li>倾斜样品用手动倾斜阶段控制旋钮45°或通过输入在"倾斜"字段45°在ESEM软件的"坐标"标签。专注于最高的样本。通过选择阶段链接到工作距离焦距|链接Z到在ESEM软件菜单FWD。输入7毫米深处"Z"字段中的控制软件中的"坐标"选项卡。 </li><li>调整的重点，stigmation，亮度和用手动控制旋钮来解决倍受关注的图像对比度。 </li></ol></li><li> 光束调节高真空模式 <ol><li>找到使用导航控件铣削的区域。 SEM图像视图内或通过手动转动的SEM阶段控制导航的x和y控制旋钮双击。 </li><li>导航到相邻的升ocation大约100微米远离研磨区域。 </li><li>查阅图1来估计所述CNT林作为压力的函数，加速电压，每像素的驻留时间，和电子束电流的材料去除速率。 </li><li>使用扫描电镜控制软件调节加速电压为30千伏和光斑尺寸为5.0。使用ESEM旋钮调整图像对焦，亮度和对比度。对于个人或少数碳纳米管的纳米级铣，选择3.0 5千伏和光斑大小。 </li><li>选择手动光圈调整1毫米的小孔。调整焦点，stigmation，亮度和对比度以获得良好分辨图象，如前面详细说明。 </li><li>减少倍率&lt;1000倍。 </li></ol></li><li> SEM安装在低压水蒸汽 <ol><li>选择11帕的控制软件下拉框的压力。 </li><li>在ESEM softwa选择在"真空"设置"低压"模式重新引入水蒸气。 </li><li>在对压力的稳定控制软件，选择"梁开"。选择&lt;10μs的停留时间和1024×884的控制软件的下拉框的决议。 </li><li>调整图像的亮度，对比度，聚焦和stigmation如前面详细介绍。 </li><li>导航到所需的铣削区域。通过选择旋转扫描图像方向|扫描旋转的控制软件，如果需要的话。选择以SEM的天然垂直和水平扫描方向对准一合适的旋转角度。 </li><li>为1微米的量级铣削的特征尺寸中，选择40000的放大倍数。选择20000倍的倍率与尺寸磨机特征最多5微米。 </li><li>通过选择&#39;"图标暂停电子束。在CNT森林的图像将被显示，并且可以被用于同时光束被暂停选择减小的面积铣削的区域。&lt;/ LI&gt; </ol></li></ol> 2. CNT林铣<ol><li> 使用矩形区域选择的指令CNT林铣 <ol><li>选择在控制软件的"面积缩小"工具，或在软件菜单中选择扫描-面积减少。延伸一个减小的区域的矩形区域上方进行研磨。 </li><li>调整图像分辨率为2,048点¯x1,768。增加的停留时间为2毫秒。如果2毫秒不可用，浏览到扫描|首选项，然后选择"扫描"选项卡。选择一个现有的扫描时间，并输入"2.0毫秒"变成了"停留时间"字段。点击"确定"关闭菜单。 </li><li>选择在控制软件&#39;"图标，激活电子束。 </li><li>选择&#39;"&#39;图标，使得光束栅格上一次所选择的区域。步骤2.1.3之后立即选择该图标，扫描持续时间取决于所选择的大小面积，分辨率和停留时间，并且可以通过扫描区域和每像素的驻留时间内乘以像素的数目来近似。 </li><li>减小放大到&lt;1,000X一旦光束完成光栅所选择的区域。恢复到在步骤1.3，其中包括高真空中使用的参数。选择"梁开"梁接触。 </li></ol></li><li> 说明CNT森林铣削沿着水平线 <ol><li>导航到选择扫描线扫描功能|线控制软件。线宽是由电子束本身的大小决定。调整从控制软件下拉框图像分辨率为2,048点¯x1,768。增加的停留时间为2毫秒如在步骤2.1.2详述。 </li><li>暂停使用电子束前获得的静止图像，在放置该地区的线路进行研磨。 </li><li>选择视频内窥镜图标或导航到扫描菜单并选择"视频内窥镜"。用Videoscope工具提供相对于当行扫描已全面完成反馈。 </li><li>选择&#39;"&#39;图标跨线的宽度进行扫描电子束。 </li><li>选择"""图标的空白电子束。 </li></ol></li><li> 用软件控制的电子束光栅扫描说明CNT林铣 <ol><li>模式生成<ol><li>设计采用CAD软件包的利益格局铣如AutoCAD。 </li><li>使用"纳米图案生成系统"（植物种质资源系统）软件，导入CAD图形文件。 </li><li>通过在植物种质资源系统软件中选择"填充多边形"转换的形状实体特征。 </li><li>将绘图另存为在植物种质资源系统的指定项目文件夹一个&#39;.dc2&#39;文件。 </li><li>利用植物种质资源系统，导航到包含".dc2"文件中的项目文件夹。右键选择".dc2"文件，并选择"运行文件编辑或"该图转换为植物种质资源系统码在给定的条件下使用，以图案的CNT森林的典型参数如下表所示: 中心到中心距离= 5纳米 行间距= 5纳米 放大率= 1万倍 所需射束电流= 26 线剂量= 100 NC /厘米</li></ol></li><li>电子束铣削用植物种质资源系统光刻软件</li><li>选择植物种质资源系统的软件按钮，在"植物种质资源系统模式"所带来的SEM到植物种质资源系统的控制权。 </li><li>突出显示模式文件，并在植物种质资源系统选择"进程中运行文件"启动铣削。 </li><li>在植物种质资源系统软件时，图案完成后，选择"SEM模式"。选择在ESEM控制软件"高真空"。 </li><li>选择"梁开"以检查研磨区域。使用步骤1.3中详述的条件。 </li></ol></li></ol> 3.样本去除<ol><li>由ESEM控制软件中选择"发泄"发泄室。 </li><li>打开门的扫描电镜。松开固定螺丝拆下存根。 </li><li>关闭箱门。选择在控制软件"高真空"。 </li></ol>

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The authors declare that they have no competing financial interests.

协议细节的最佳实践铣削比较大的（微米级）酒店在CNT森林。在一般情况下，材料移除速率可以通过降低加速电压，光斑尺寸以及孔直径被减小。到一个森林内修剪特定的CNT，推荐的条件包括5千伏，为3的光斑尺寸，和孔径是50微米或更小的直径。注意，使用减少了面积的矩形的研磨技术中详细说明，使得电子束栅格封闭区域仅一次。如果附加的切削深度需要降低的区域可被扫描多次;然而，我们?...

碳纳米管（CNT）和石墨烯是基于碳的纳米材料已经引起因其优越的强度，耐用性，热和电性能显著关注。碳纳米材料的精密加工成为一个新兴的研究课题，并提供给设计并朝各种工程应用操纵这些材料的潜力。加工碳纳米管和石墨烯需要纳米级的空间精度首先定位感兴趣的纳米区域，然后以选择性的感兴趣的区域内仅去除材料。作为一个例子，考虑垂直取向的碳纳米管林的加工（也称为碳纳米管阵列）。碳纳米管林的横截面可以通过催化剂膜的光刻图案形成精确限定。的垂直取向的森林的顶面，但是，经常具有非均匀的高度有序很差。对于表面敏感的应用，如热界面材料，叔他不规则表面可能会阻碍最佳表面接触并降低器件的性能。不规则表面以产生均匀的平坦表面的精度微调可以通过最大化可用的接触面积可能提供更好，更可重复的性能。 纳米材料的精密加工技术经常不象传统的宏观机械加工技术，例如钻孔，铣削和抛光由硬化模具的装置。迄今为止，使用能束技术已经最成功的碳纳米部位选择性铣削。这些技术包括激光，电子束和聚焦离子束（FIB）照射。这些中，激光加工技术提供了最快速的材料去除速率1,2;然而，激光系统的光点尺寸是许多微米的量级和过大以分离纳米级实体，例如一个碳Ñ一个人口稠密的林内anotube段。与此相反，电子和离子束系统产生可以聚焦到一个点是几纳米或更小直径的光束。 FIB系统是专门为纳米级铣削和材料沉积而设计的。这些系统利用气态金属离子的能量束（通常为镓）以从选定的区域溅射材料。 CNT的FIB研磨是可以实现的，但常常有意想不到的副产物，包括在围绕森林3,4的区域镓和碳的再沉积。当该技术被用于CNT森林，再沉积材料掩模和/或改变选择的研磨区域的形态，改变该CNT森林的天然外观和行为。镓也可以在CNT内植入，提供电子掺杂。这样的后果往往使基于FIB铣削望而却步CNT的森林。 5，通过TEM产生的电子能量足以直接从CNT晶格删除原子和诱导高度本地化的铣削。该技术钢厂碳纳米管具有潜在亚纳米精度5，6，7;然而，这个过程是很慢的 - 通常需要几分钟到磨机单个的CNT。重要的是，基于TEM-铣削方法需要首先从生长衬底移除并分散在TEM网格进行处理的CNT。其结果是，基于TEM-方法一般不与碳纳米管林铣削，其中碳纳米管必须保持刚性基板上兼容。 CN铣削<html> ŧ森林通过扫描电子显微镜（中小型企业）也受到了关注。相反，TEM-基础的技术，SEM工具通常无法加速有足够能量的电子传授给直接删除碳原子所需的连锁能量。相反，基于SEM-技术利用在低压的气态氧化剂的存在下的电子束。该电子束有选择地损害该CNT晶格，并且可以离解的气体环境为更反应性物质如H 2 O 2和羟基自由基。水蒸气和氧气是最常见的气体来实现选择性区域蚀刻。因为基于SEM-技术依赖于多步化学处理，大量的加工变量可能影响该方法的研磨速率和精度。先前已观察到增加的加速电压和电子束电流直接增加，因为增加的能量通量的研磨速率，如预期"外部参照"&gt; 11。室压力的效果不太明显。过低的压力从氧化剂的缺乏症，降低研磨速度。此外，气态物质的过度丰富散射的电子束并降低电子通量在铣削区域，也减少了材料去除速率。 估算碳去除率，一种方法类似于由拉西特用于和架12被采用，由此电子与表面附近的前体分子相互作用以产生蚀刻衬底表面反应性物质。从这个模型，蚀刻速率被估计为<img alt="方程" src="/files/ftp_upload/55149/55149eq1.jpg" />其中N A是蚀刻剂物种的表面浓度，Z是可用的反应位点的表面浓度，x是与挥发性蚀刻化学计量因子相对于反应物生成的产物中，Aσ表示从电子水蒸汽碰撞产生所需的蚀刻物种的概率，并γE是在表面的电子通量。 X和Aσ的因素被假定为统一，而Z为假定为几乎恒定并且比NA显著大。进一步的细节可以在我们以前的工作中找到。 11 在这篇文章中，过程进行了探讨，使用低压水蒸汽的SEM内磨区，从个人到碳纳米管体积大（几十立方微米）的材料去除。在这里，我们证明用于使用通过使用减小的面积的矩形，水平行扫描和电子束的软件控制的光栅扫描的ESEM磨碳纳米管林的技术。附加的软件和硬件都需要图案生成，如在材料清单中概述。重点放在相对移除LY大（立方微米的100的）由CNT森林材料体积，所以下面的加工条件相对激进。 当处理样品并把样品存根，它穿一次性腈手套是重要的。这将防止油被传递到存根或样品并因此恶化了泵的效率。

<table><tbody><tr><td>100 mm diameter silicon wafer with 1 micron thermal oxide</td><td>University Wafer</td><td></td><td>Beginning substrate</td></tr><tr><td>Iron sputter target</td><td>Kurt J. Lesker</td><td>EJTFEXX351A2</td><td>Sputter target&amp;nbsp;</td></tr><tr><td>Savannah 200</td><td>Cambridge</td><td></td><td>For atomic layer deposition of alumina</td></tr><tr><td>Quanta 600F Environmental SEM</td><td>FEI</td><td></td><td>Environmental scanning electron microscope used to support a low-pressure water vapor ambient environment for CNT forest milling</td></tr><tr><td>xT Microscope Control software</td><td>FEI</td><td>4.1.7</td><td>Control software used on Quanta 600F ESEM</td></tr><tr><td>Nanometer Pattern Generation System - Software</td><td>JC Nabity Lithography Systems</td><td>Version 9</td><td>Software used for electron-beam lithography</td></tr><tr><td>Dedicated computer with PCI516 Lithography board</td><td></td><td></td><td>Equipment used for electron-beam lithography</td></tr><tr><td>DesignCAD software</td><td></td><td>V 21.2</td><td>Optional equipment used to generate patterns for electron-beam lithography</td></tr><tr><td>E-beam lithography mount</td><td>Ted Pella</td><td>16405</td><td>Electron beam lithography mount with a Faraday cup and gold nanoparticles on carbon tape</td></tr><tr><td>Picoammeter</td><td>Keithley</td><td>6485</td><td>Used with the Faraday cup to quantify beam current</td></tr><tr><td>12.7 mm diameter SEM stub</td><td>Ted Pella</td><td>16111</td><td>SEM stub</td></tr><tr><td>45 degree pin stub holder</td><td>Ted Pella</td><td>15329</td><td>Optional equipment used to mill the cross section of a CNT forest</td></tr></tbody></table>

precision milling of carbon nanotube forests using low pressure scanning electron microscopy

A nanoscale fabrication technique appropriate for milling carbon nanotube (CNT) forests is described. The technique utilizes an environmental scanning electron microscope (ESEM) operating with a low pressure water vapor ambient. In this technique, a portion of the electron beam interacts with the water vapor in the vicinity of the CNT sample, dissociating the water molecules into hydroxyl radicals and other species by radiolysis. The remainder of the electron beam interacts with the CNT forest sample, making it susceptible to oxidation from the chemical products of radiolysis. This technique may be used to trim a selected region of an individual CNT, or it may be used to remove hundreds of cubic microns of material by adjusting ESEM parameters. The machining resolution is similar to the imaging resolution of the ESEM itself. The technique produces only small quantities of carbon residue along the boundaries of the cutting zone, with minimal effect on the native structural morphology of the CNT forest.

该ESEM技术被用来磨使用热CVD 15,16的CNT林合成。从森林内选定区域去除一些CNT的示于图2 11。对于这个示范，参数包括5千伏，3点尺寸，11帕，170,000X放大率，2毫秒的停留时间，和30微米的孔。 表现出较大规模的区域去除，被选定的CNT森林微柱的顶面进行?...

Watch this Scientific Journal Video about Precision Milling of Carbon Nanotube Forests Using Low Pressure Scanning Electron Microscopy at JoVE.com

Precision Milling of Carbon Nanotube Forests Using Low Pressure Scanning Electron Microscopy

Low pressure scanning electron microscopy in a water vapor ambient is used to machine nanoscale to microscale features in carbon nanotube forests.

碳纳米管森林精密铣床使用低压扫描电子显微镜

A nanoscale fabrication technique appropriate for milling carbon nanotube (CNT) forests is described. The technique utilizes an environmental scanning ...

precision-milling-carbon-nanotube-forests-using-low-pressure-scanning

Research

JoVE Journal

Engineering

7.4K 次观看.  University of Missouri. Low pressure scanning electron microscopy in a water vapor ambient is used to machine nanoscale to microscale features in carbon nanotube forests.

视频: Precision Milling of Carbon Nanotube Forests Using Low Pressure Scanning Electron Microscopy

Fabrication, Densification, and Replica Molding of 3D Carbon Nanotube Microstructures

The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, lab-on-a-chip devices, and their applications. In particular, capabilities for cost-effective fabrication of polymer microstructures were transformed by the advent of soft lithography and other micromolding techniques 1, 2, and this led a revolution in applications of microfabrication to biomedical engineering and biology. Nevertheless, it remains challenging to fabricate microstructures with well-defined nanoscale surface textures, and to fabricate arbitrary 3D shapes at the micro-scale. Robustness of master molds and maintenance of shape integrity is especially important to achieve high fidelity replication of complex structures and preserving their nanoscale surface texture. The combination of hierarchical textures, and heterogeneous shapes, is a profound challenge to existing microfabrication methods that largely rely upon top-down etching using fixed mask templates. On the other hand, the bottom-up synthesis of nanostructures such as nanotubes and nanowires can offer new capabilities to microfabrication, in particular by taking advantage of the collective self-organization of nanostructures, and local control of their growth behavior with respect to microfabricated patterns. 
Our goal is to introduce vertically aligned carbon nanotubes (CNTs), which we refer to as CNT "forests", as a new microfabrication material. We present details of a suite of related methods recently developed by our group: fabrication of CNT forest microstructures by thermal CVD from lithographically patterned catalyst thin films; self-directed elastocapillary densification of CNT microstructures; and replica molding of polymer microstructures using CNT composite master molds. In particular, our work shows that self-directed capillary densification ("capillary forming"), which is performed by condensation of a solvent onto the substrate with CNT microstructures, significantly increases the packing density of CNTs. This process enables directed transformation of vertical CNT microstructures into straight, inclined, and twisted shapes, which have robust mechanical properties exceeding those of typical microfabrication polymers. This in turn enables formation of nanocomposite CNT master molds by capillary-driven infiltration of polymers. The replica structures exhibit the anisotropic nanoscale texture of the aligned CNTs, and can have walls with sub-micron thickness and aspect ratios exceeding 50:1. Integration of CNT microstructures in fabrication offers further opportunity to exploit the electrical and thermal properties of CNTs, and diverse capabilities for chemical and biochemical functionalization 3.

We present methods for fabrication of patterned microstructures of vertically aligned carbon nanotubes (CNTs), and their use as master molds for production of polymer microstructures with organized nanoscale surface texture. The CNT forests are densified by condensation of solvent onto the substrate, which significantly increases their packing density and enables self-directed formation of 3D shapes.

制备，致密，副本三维碳纳米管微结构成型

The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, lab-on-a-chip ...

科研

工程学

Simultaneous Synthesis of Single-walled Carbon Nanotubes and Graphene in a Magnetically-enhanced Arc Plasma

Carbon nanostructures such as single-walled carbon nanotubes (SWCNT) and graphene attract a deluge of interest of scholars nowadays due to their very promising application for molecular sensors, field effect transistor and super thin and flexible electronic devices1-4. Anodic arc discharge supported by the erosion of the anode material is one of the most practical and efficient methods, which can provide specific non-equilibrium processes and a high influx of carbon material to the developing structures at relatively higher temperature, and consequently the as-synthesized products have few structural defects and better crystallinity.
 To further improve the controllability and flexibility of the synthesis of carbon nanostructures in arc discharge, magnetic fields can be applied during the synthesis process according to the strong magnetic responses of arc plasmas. It was demonstrated that the magnetically-enhanced arc discharge can increase the average length of SWCNT 5, narrow the diameter distribution of metallic catalyst particles and carbon nanotubes 6, and change the ratio of metallic and semiconducting carbon nanotubes 7, as well as lead to graphene synthesis 8. 
 Furthermore, it is worthwhile to remark that when we introduce a non-uniform magnetic field with the component normal to the current in arc, the Lorentz force along the J&times;B direction can generate the plasmas jet and make effective delivery of carbon ion particles and heat flux to samples. As a result, large-scale graphene flakes and high-purity single-walled carbon nanotubes were simultaneously generated by such new magnetically-enhanced anodic arc method. Arc imaging, scanning electron microscope (SEM), transmission electron microscope (TEM) and Raman spectroscopy were employed to analyze the characterization of carbon nanostructures. These findings indicate a wide spectrum of opportunities to manipulate with the properties of nanostructures produced in plasmas by means of controlling the arc conditions.

Anodic arc discharge is one of the most practical and efficient methods to synthesize various carbon nanostructures. To increase the arc controllability and flexibility, a non-uniform magnetic field was introduced to process the one-step synthesis of large-scale graphene flakes and high-purity single-walled carbon nanotubes.

同时合成单壁碳纳米管和石墨在电弧等离子体磁增强

Carbon nanostructures such as single-walled carbon nanotubes (SWCNT) and graphene attract a deluge of interest of scholars nowadays due to their very ...

生物工程

Atomic Force Microscopy of Red-Light Photoreceptors Using PeakForce Quantitative Nanomechanical Property Mapping

Atomic force microscopy (AFM) uses a pyramidal tip attached to a cantilever to probe the force response of a surface. The deflections of the tip can be measured to ~10 pN by a laser and sectored detector, which can be converted to image topography. Amplitude modulation or &#8220;tapping mode&#8221; AFM involves the probe making intermittent contact with the surface while oscillating at its resonant frequency to produce an image. Used in conjunction with a fluid cell, tapping-mode AFM enables the imaging of biological macromolecules such as proteins in physiologically relevant conditions. Tapping-mode AFM requires manual tuning of the probe and frequent adjustments of a multitude of scanning parameters which can be challenging for inexperienced users. To obtain high-quality images, these adjustments are the most time consuming.
PeakForce Quantitative Nanomechanical Property Mapping (PF-QNM) produces an image by measuring a force response curve for every point of contact with the sample. With ScanAsyst software, PF-QNM can be automated. This software adjusts the set-point, drive frequency, scan rate, gains, and other important scanning parameters automatically for a given sample. Not only does this process protect both fragile probes and samples, it significantly reduces the time required to obtain high resolution images. PF-QNM is compatible for AFM imaging in fluid; therefore, it has extensive application for imaging biologically relevant materials.
The method presented in this paper describes the application of PF-QNM to obtain images of a bacterial red-light photoreceptor, RpBphP3 (P3), from photosynthetic R. palustris in its light-adapted state. Using this method, individual protein dimers of P3 and aggregates of dimers have been observed on a mica surface in the presence of an imaging buffer. With appropriate adjustments to surface and/or solution concentration, this method may be generally applied to other biologically relevant macromolecules and soft materials.

A method for investigating the structure of a protein photoreceptor using atomic force microscopy (AFM) is described in this paper. PeakForce Quantitative Nanomechanical Property Mapping (PF-QNM) reveals intact protein dimers on a mica surface.

冲红灯光感受器原子力显微镜使用PeakForce定量纳米机械性能映射

Atomic force microscopy (AFM) uses a pyramidal tip attached to a cantilever to probe the force response of a surface. The deflections of the tip can be ...

Fabrication of Low Temperature Carbon Nanotube Vertical Interconnects Compatible with Semiconductor Technology

We demonstrate a method for the low temperature growth (350 &#176;C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive thin-films. Due to the low growth temperature, the process allows integration with modern low-&#954; dielectrics and some flexible substrates. The process is compatible with standard semiconductor fabrication, and a method for the fabrication of electrical 4-point probe test structures for vertical interconnect test structures is presented. Using scanning electron microscopy the morphology of the CNT bundles is investigated, which demonstrates vertical alignment of the CNT and can be used to tune the CNT growth time. With Raman spectroscopy the crystallinity of the CNT is investigated. It was found that the CNT have many defects, due to the low growth temperature. The electrical current-voltage measurements of the test vertical interconnects displays a linear response, indicating good ohmic contact was achieved between the CNT bundle and the top and bottom metal electrodes. The obtained resistivities of the CNT bundle are among the average values in the literature, while a record-low CNT growth temperature was used.

A method for the growth of low temperature vertically-aligned carbon nanotubes, and the subsequent fabrication of vertical interconnect electrical test structures using semiconductor fabrication is presented.

低温碳纳米管垂直互连的制作兼容半导体技术

We demonstrate a method for the low temperature growth (350 &#176;C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive ...

Functionalization of Single-walled Carbon Nanotubes with Thermo-reversible Block Copolymers and Characterization by Small-angle Neutron Scattering

We demonstrate a protocol for single-walled carbon nanotube functionalization using thermo-sensitive PEO-PPO-PEO triblock copolymers in an aqueous solution. In a carbon nanotube/PEO105-PPO70-PEO105 (poloxamer 407) aqueous solution, the amphiphilic poloxamer 407 adsorbs onto the carbon nanotube surfaces and self-assembles into continuous layers, driven by intermolecular interactions between constituent molecules. The addition of 5-methylsalicylic acid changes the self-assembled structure from spherical-micellar to a cylindrical morphology. The fabricated poloxamer 407/carbon nanotube hybrid particles exhibit thermo-responsive structural features so that the density and thickness of poloxamer 407 layers are also reversibly controllable by varying temperature. The detailed structural properties of the poloxamer 407/carbon nanotube particles in suspension can be characterized by small-angle neutron scattering experiments and model fit analyses. The distinct curve shapes of the scattering intensities depending on temperature control or addition of aromatic additives are well described by a modified core-shell cylinder model consisting of a carbon nanotube core cylinder, a hydrophobic shell, and a hydrated polymer layer. This method can provide a simple but efficient way for the fabrication and in-situ characterization of carbon nanotube-based nano particles with a structure-tunable encapsulation.

A method for the functionalization of carbon nanotubes with structure-tunable polymeric encapsulation layers and structural characterization using small-angle neutron scattering is presented.

单壁碳纳米管与热可逆嵌段共聚物及表征功能化小角度中子散射

We demonstrate a protocol for single-walled carbon nanotube functionalization using thermo-sensitive PEO-PPO-PEO triblock copolymers in an aqueous ...

化学

Fabrication of Carbon Nanotube High-Frequency Nanoelectronic Biosensor for Sensing in High Ionic Strength Solutions

The unique electronic properties and high surface-to-volume ratios of single-walled carbon nanotubes (SWNT) and semiconductor nanowires (NW) 1-4 make them good candidates for high sensitivity biosensors. When a charged molecule binds to such a sensor surface, it alters the carrier density5 in the sensor, resulting in changes in its DC conductance. However, in an ionic solution a charged surface also attracts counter-ions from the solution, forming an electrical double layer (EDL). This EDL effectively screens off the charge, and in physiologically relevant conditions ~100 millimolar (mM), the characteristic charge screening length (Debye length) is less than a nanometer (nm). Thus, in high ionic strength solutions, charge based (DC) detection is fundamentally impeded6-8.
We overcome charge screening effects by detecting molecular dipoles rather than charges at high frequency, by operating carbon nanotube field effect transistors as high frequency mixers9-11. At high frequencies, the AC drive force can no longer overcome the solution drag and the ions in solution do not have sufficient time to form the EDL. Further, frequency mixing technique allows us to operate at frequencies high enough to overcome ionic screening, and yet detect the sensing signals at lower frequencies11-12. Also, the high transconductance of SWNT transistors provides an internal gain for the sensing signal, which obviates the need for external signal amplifier.
Here, we describe the protocol to (a) fabricate SWNT transistors, (b) functionalize biomolecules to the nanotube13, (c) design and stamp a poly-dimethylsiloxane (PDMS) micro-fluidic chamber14 onto the device, and (d) carry out high frequency sensing in different ionic strength solutions11.

We describe the device fabrication and measurement protocol for carbon nanotube based high frequency biosensors. The high frequency sensing technique mitigates the fundamental ionic (Debye) screening effect and allows nanotube biosensor to be operated in high ionic strength solutions where conventional electronic biosensors fail. Our technology provides a unique platform for point-of-care (POC) electronic biosensors operating in physiologically relevant conditions.

制备碳纳米管高频纳电子生物传感器的传感高离子强度的解决方案

The unique electronic properties and high surface-to-volume ratios of single-walled carbon nanotubes (SWNT) and semiconductor nanowires (NW) 1-4 make them ...

Single-Digit Nanometer Electron-Beam Lithography with an Aberration-Corrected Scanning Transmission Electron Microscope

We demonstrate extension of electron-beam lithography using conventional resists and pattern transfer processes to single-digit nanometer dimensions by employing an aberration-corrected scanning transmission electron microscope as the exposure tool. Here, we present results of single-digit nanometer patterning of two widely used electron-beam resists: poly (methyl methacrylate) and hydrogen silsesquioxane. The method achieves sub-5 nanometer features in poly (methyl methacrylate) and sub-10 nanometer resolution in hydrogen silsesquioxane. High-fidelity transfer of these patterns into target materials of choice can be performed using metal lift-off, plasma etch, and resist infiltration with organometallics.

We use an aberration-corrected scanning transmission electron microscope to define single-digit nanometer patterns in two widely-used electron-beam resists: poly (methyl methacrylate) and hydrogen silsesquioxane. Resist patterns can be replicated in target materials of choice with single-digit nanometer fidelity using liftoff, plasma etching, and resist infiltration by organometallics.

用畸变校正扫描透射电镜进行单数字纳米电子束光刻

We demonstrate extension of electron-beam lithography using conventional resists and pattern transfer processes to single-digit nanometer dimensions by ...

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 ...

Microscopic Visualization of Porous Nanographenes Synthesized through a Combination of Solution and On-Surface Chemistry

On-surface synthesis has recently been regarded as a promising approach for the generation of new molecular structures. It has been particularly successful in the synthesis of graphene nanoribbons, nanographenes and intrinsically reactive and instable, yet attractive species. It is based on the combination of solution chemistry aimed at preparation of appropriate molecular precursors for further ultra-high vacuum surface assisted transformations. This approach also owes its success to an incredible development of characterization techniques, such as scanning tunneling/atomic force microscopy and related methods, which allow detailed, local characterization at atomic scale. While the surface-assisted synthesis can provide molecular nanostructures with outstanding precision, down to single atoms, it suffers from basing on metallic surfaces and often limited yield. Therefore, the extension of the approach away from metals and the struggle to increase productivity seem to be significant challenges toward wider applications. Herein, we demonstrate the on-surface synthesis approach for generation of non-planar nanographenes, which are synthesized through a combination of solution chemistry and sequential surface-assisted processes, together with the detailed characterization by scanning probe microscopy methods.

<meta charset="utf8"></head><body>通过溶液和表面化学相结合合成的多孔纳米石墨烯的微观可视化

A combination of solution and surface assisted synthesis opens new directions in the atomically precise synthesis of nanostructures. Scanning tunneling microscopy (STM) supplemented by non-contact atomic force microscopy (nc-AFM) enables detailed characterization of newly designed and generated carbon-based nano-objects.