Name: flow-assisted dielectrophoresis: a low cost method for the fabrication of high performance solution-processable nanowire devices
Uploaded: 2017-12-07T14:00:00.000+00:00
Duration: 9 min 14 s
Description: Watch this Scientific Journal Video about Flow-assisted Dielectrophoresis: A Low Cost Method for the Fabrication of High Performance Solution-processable Nanowire Devices at JoVE.com

作者想感谢 ESPRC 和 BAE 系统的财政支持, 和 Prof. 布莱恩 a. Korgel 和他的小组供应的 SFLS 生长硅纳米线用于这项工作。

警告: 除非另有规定, 所有的程序都要在干净的房间环境中进行, 并进行风险评估, 以确保纳米线和化学品处理过程中的安全。纳米材料可能有许多健康方面的影响, 这是未知的, 所以应该处理适当的照顾21。
注: 该过程从基板的制备开始, 然后是第一个光刻和金属沉积步骤来定义 DEP 接触。然后通过 DEP 组装纳米线, 再选择一个可选的光刻和金属沉积步骤, 将顶端接触物沉积到纳米线上。纳米线晶体管器件的电流电压特性, 然后使用半导体表征套件测量。
1. 基板的制备
<ol><li>将掺杂的 n 型硅/二氧化硅晶片切割成合适的尺寸,例如, 2.5 厘米2。</li>
	<li>在切割过程中, 确保晶片的顶面不被触及或划伤。</li>
	<li>在一个连续的运动中, 用一个钻石划线在表面上进行切割。</li>
	<li>沿切口拆下晶片。</li>
	<li>将样品放在基板上, 在超音波浴中几种5分钟, 在100% 功率 (450 W), 先是在去离子水中, 然后是丙酮, 最后是异丙醇 (国际音标)。 注意: 请参阅 CAS 编号和供应商的材料表。</li>
	<li>用氮气枪擦干基板, 去除表面上的任何残留的国际音标或灰尘。</li>
	<li>血浆灰分在氧等离子体中的样品在 100 W 为5分钟, 除去任何残留的有机残渣。</li>
</ol>2. 接触用光刻双层工艺
注: 双层光刻工艺用于制造电极。光刻工艺在一个黄色的房间进行, 以防止光刻胶材料的衰变。
<ol><li>用板将样品在150° c 下加热15分钟, 从表面除去任何剩余的水分。 注: 这是为了保证光刻胶的附着力;然而化学底漆例如 HMDS 也可能使用。</li>
	<li>从热板中取出样品, 并将其放在旋转涂布机上。</li>
	<li>使用吸管, 下降约1毫升的光刻胶在表面上, 直到整个样品被统一覆盖。 注: 有关所用的精确光刻胶, 请参见材料表。</li>
	<li>旋转样品在 4000 rpm 为四十五年代, 生产大约250毫微米的影片厚度。如果要沉积的电极厚度大于 150 nm, 请更改此配方。</li>
	<li>将样品从自旋涂布机上取出, 放在150° c 的板上5分钟。</li>
	<li>从板中取出样品, 并将样品留在50% 湿度箱中休息5分钟。这是为了确保抗蚀剂的复水性22。 注: 如果实验室的湿度大于 50%, 则可以将样品留在空气中休息。</li>
	<li>将样品放回自旋涂布机上, 将大约1毫升的抗蚀剂 B 放在基板表面。</li>
	<li>旋转样品在 3500 rpm 为四十五年代, 给影片厚度大约500毫微米。</li>
	<li>将样品放在120° c 的板上2分钟。</li>
	<li>从板中取出样品, 在50% 的湿度箱中休息5分钟。</li>
	<li>暴露样品使用面罩-器和掩紫外线的6.7 秒, 共180兆焦耳的曝光。 注意: 确切的曝光剂量可能需要根据特定型号的面膜器进行调整。</li>
	<li>从面具器中取出样品, 并在三十年代将其浸入光刻胶显影液中进行开发。 注意: 有关确切的开发人员, 请参见材料表。</li>
	<li>从显影液中取出样品, 将样品浸入去离子水中, 冲洗, 以停止开发过程。</li>
	<li>使用光学显微镜检查影印。偏光片可以用来检查双层咬边, 它应该出现在通道周围的微弱线上。如果达到太多或两个小的缺口, 则可以调整时间。</li>
</ol>3. 金属接触物的沉积
注: 电子束 (电子束) 沉积用于将电极沉积在所制备的光刻胶上。这个过程也可以使用热蒸发器或其他类型的金属薄膜沉积技术。
<ol><li>将样品放在电子束室中;把它抽下去直到达到高真空。在这种情况下, 达到了大约 1 x 10-6 mTorr 的真空。</li>
	<li>沉积 2-6 纳米钛, 作为一个黏附层, 其次为30纳米黄金的 DEP 接触。</li>
	<li>从电子束室中取出样品。</li>
	<li>通过去除大部分的光刻胶和多余的金属来执行升降过程。这是通过把样品放入一烧杯的光刻胶卸妆15分钟。</li>
	<li>从光刻胶的烧杯中取出样品, 再将其放入另一干净的光刻胶中15分钟。这是为了防止任何大型金属微粒沉淀在样品上。</li>
	<li>完成 sonicating 的烧杯5分钟, 在50% 功率。</li>
	<li>从浴缸中取出样品, 确保用国际音标冲洗掉任何材料, 防止金属微粒在电极间沉淀。 注: 电极现在为纳米线的 DEP 校准做好准备。</li>
</ol>4. 纳米线的 DEP
<ol><li>在大约1µg/毫升浓度的甲醚中制备硅或其他纳米线的溶液。在这个实验中, 解决方案是简要声十五年代在最低功率设置可能消除任何絮凝。其他溶剂可以使用, 如甲苯和 n, n-胺 (DMF)1。</li>
	<li>通过将纳米线配方的10µL 放在牺牲基底上来检查溶液。</li>
	<li>使用偏光显微镜 (POM) 检查基板的沉积纳米线。硅纳米线是双折射的, 因此可以很容易地在 POM 中看到。如果没有纳米线的团簇可见, 并且大部分的纳米导线在基体上都有很好的分散, 那么下一阶段就可以开始, 否则溶液是重新声的, 并且可能需要调整纳米丝的浓度。它可能需要几次尝试, 以实现正确的纳米线分散。</li>
	<li>将准备好的样品与电极放置在30° (vs. 地平线) 倾斜平台上, 设备通道水平对齐。色散流方向需要垂直于电极边缘, 以使纳米线对齐更加有效。</li>
	<li>使用连接到频率发生器1的微探针与电极接触。</li>
	<li>设置所需的频率和电压在频率发生器上。在本实验中, 使用10伏峰值和 1 MHz 正弦波的 DEP 信号电压。 注: 增加20兆赫的频率可以帮助收集高电导率和低阱密度的纳米线1,2。有关详细讨论, 请参见参考1 。本文所述的 DEP 信号频率范围是通过导电 SFLS 硅纳米线阻抗谱和收集时间分析得到的, 如参考1所示。其他类型的高或低电荷载流子移动性纳米线, 掺杂纳米线, 或其他生长方法获得的纳米线, 可以有不同的 DEP 信号频率范围, 导致收集高质量的纳米线。</li>
	<li>开关-在频率发生器和下降约10µL 纳米线解决方案使用微到设备区域。 注: 将样品置于一个角度 (30 °) 有助于产生重力辅助的液体缓慢流动。或者, 使用玻璃幻灯片的毛细管操作可以使用6。</li>
	<li>应用三十年代的 DEP 信号, 然后关掉频率发生器。</li>
	<li>取出样品, 用国际音标轻轻冲洗。</li>
	<li>用氮气枪轻轻地把样品干掉。偏振光学显微镜可用于检测样品和调整参数 注: DEP 信号的电压、频率和纳米线的色散密度可进行调整, 以实现可重现的纳米导线密度, 从数个纳米线到每设备1,2。</li>
</ol>5. 二次金属层的沉积
<ol><li>为了在 NW fet 中获得改进的电流注入, 在纳米线的顶端应用第二个金属接触。 注: 此接触沉积过程遵循与2和3节完全相同的步骤, 在光刻和金属沉积, 但只有一个金层的沉积。</li>
</ol>6. 纳米线器件的 i-v 特性
注: 样品现已完成, 可用于后续实验或其 i-v 特性可以测量, 以建立纳米线 FET 的电性能。所制备的器件为后门式 fet, 掺杂硅晶片作为共用栅极, 而2层则充当栅极电介质。
<ol><li>要与栅极建立电接点, 请使用菱形划线在试样边缘移除一个小面积的氧化硅。</li>
	<li>使用氮气枪清除任何不需要的二氧化硅粒子。</li>
	<li>安置三探针 (来源、流失和门) 在金子来源-流失电极联络, 与门探针在区域与被去除的一点的2。</li>
	<li>使用半导体表征系统进行 i-v 测量。</li>
	<li>测量传输和输出扫描的 NW fet, 因为这些提供有关设备性能的信息和纳米线的电气性能1,17,23。请注意, 传输测量涉及步进源-漏电压和扫门电压。通过扫源电压和步进门电压来测量输出特性。</li>
</ol>

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作者证实没有利益冲突。

器件的成功制造和性能取决于几个关键因素。这些包括纳米线的密度和在配方中的分布, 溶剂的选择, DEP 的频率, 以及对器件电极上存在的纳米导线数量的控制1。
实现可重复工作装置的关键步骤之一是制备无簇或块状的纳米线配方。该配方可声前, 以减少团簇数量和保持纳米线分散。一个溶液的密度一旦被制造, 也很难控制, 特别是如果纳米线可能凝固, 这可?...

纳米粒子在预先定义的基底位置的可控性和可再生性组装是利用半导体或导电纳米粒子的解决方案处理的电子和光子器件的主要挑战之一。对于高性能器件来说, 能够选择具有优先尺寸的纳米粒子, 以及特殊的电子特性, 包括高导电性和低密度的表面陷阱状态, 也是非常有益的。尽管纳米线和纳米管材料的发展有了很大的进展, 但纳米粒子的某些特性始终存在, 选择步骤可以显著改善纳米粒子的性能1 ,2。
在这项工作中演示的流辅助 DEP 方法的目的是通过向高性能纳米线场效应晶体管显示可控的半导体纳米导线组装到金属触点上来解决上述挑战。dep 解决了纳米线器件制造中的几个问题, 包括纳米导线的定位、纳米线的对准/定位、以及所需性能的纳米线的选择via dep 信号频率选择1。DEP 已用于许多其他设备, 从气体传感器3, 晶体管1, 和 RF 开关4,5, 到细菌的定位分析7。
DEP 是通过非均匀电场的应用来操纵极化粒子, 从而使纳米线在电极上的自组装成为8。该方法最初是为操作细菌而开发的9,10 , 但此后已扩展到对纳米线和纳米材料的操作。
纳米粒子的 DEP 解决方案使半导体器件的制造与传统的基于多 photomasking、离子注入、高温14、退火和蚀刻的顶向下技术截然不同。步骤.由于 DEP 操作已经合成的纳米粒子, 所以它是一种低温、自下而上的制作技术11。这种方法允许大型纳米线器件在几乎任何基板上组装, 包括温度敏感、柔性塑料衬底6、12、13。
在这项工作中, 使用流辅助 DEP 制作高性能 p 型硅纳米线场效应晶体管, 并进行 FET 电流电压特性表征。这项工作中使用的硅纳米线是通过超级流体固体 (SFLS) 方法15,16来发展的。纳米线被有意掺杂, 直径约 10-50 µm, 长度为 30-40 nm。SFLS 的生长方法是非常诱人的, 因为它可以提供行业可伸缩的数量的纳米线材料15。所提出的纳米线组装方法直接适用于其他半导体纳米线材料, 如 InAs13、诺23和 GaN18。该技术还可以扩展到对齐导电纳米线19 , 并将纳米粒子置于电极间隙位置20。

<table><tbody><tr><td>Silicon/silicon dioxide wafer, CZ method growth, 100mm diameter,&amp;nbsp; 300 nm oxide thermal growth,&amp;nbsp; n-doped phosphorus</td><td>Si-Mat (Silicon materials)</td><td>-</td><td>http://si-mat.com/</td></tr><tr><td>Acetone (200ml)</td><td>Sigma Aldrich</td><td>W332615</td><td>-</td></tr><tr><td>Isopropanol (200ml)</td><td>Sigma Aldrich</td><td>W292907</td><td>-</td></tr><tr><td>Deionised water (150ml)</td><td>On site supply</td><td>-</td><td>-</td></tr><tr><td>Photoresist (A) SF6 PMGI under etch photoresit (approx 1 ml per sample)</td><td>Microchem&amp;nbsp;</td><td>-</td><td>http://microchem.com/pdf/PMGI-Resists-data-sheetV-rhcedit-102206.pdf</td></tr><tr><td>Photoresist (B) S1805 photoresit) (approx 1 ml per sample)</td><td>Microchem&amp;nbsp;</td><td>-</td><td>http://www.microchem.com/PDFs_Dow/S1800.pdf</td></tr><tr><td>Photoresist developer Microposit&amp;nbsp; MF319&amp;nbsp; (100ml)</td><td>Microchem&amp;nbsp;</td><td>-</td><td>http://microchem.com/products/images/uploads/MF_319_Data_Sheet.pdf</td></tr><tr><td>Photoresist remover Microposit remover 1165 (300ml (2 baths 150 each))</td><td>Microchem&amp;nbsp;</td><td>-</td><td>http://micromaterialstech.com/wp-content/dow_electronic_materials/datasheets/1165_Remover.pdf</td></tr></tbody></table>

flow-assisted dielectrophoresis: a low cost method for the fabrication of high performance solution-processable nanowire devices

流辅助介 (DEP) 是一种高效的自组装方法, 可用于纳米线的可控、可重复定位、对准和选择。DEP 用于纳米线的分析、表征以及基于溶液的半导体器件的制造。该方法的工作原理是在金属电极之间应用交流电场。纳米线的配方, 然后下降到电极上, 在一个倾斜的表面, 以创造一个流动的配方使用重力。然后, 纳米线沿着电场的梯度和液体流动的方向排列。该场的频率可以调整, 以选择具有优越的导电率和较低的陷阱密度纳米线。
在这项工作中, 流辅助 DEP 用于创建纳米线场效应晶体管。流动辅助 DEP 有几个优点: 它允许选择纳米线的电学性质;纳米线长度的控制;纳米线在特定区域的放置;纳米线定向的控制;和控制纳米线密度的装置。
该技术可以扩展到许多其他应用, 如气体传感器和微波开关。该技术效率高、速度快、重现性好, 使用了少量的稀溶液, 使其适合于新型纳米材料的测试。纳米线器件的晶片规模组装也可以使用这种技术实现, 允许大量的样品用于测试和大面积电子应用。

双层光刻结果在清洁尖锐定义的电极。在示例 (图 1A) 中, digitated 的手指结构使用了10µm 的通道长度。当应用 DEP 力时, 这些结构允许大面积的纳米线的最大数目聚集。图 1B显示了底部栅纳米线 FET 装置的示意图。
不正确的纳米线分散浓度, 以及不足的超声可能导致质量较差的分散体, ...

Watch this Scientific Journal Video about Flow-assisted Dielectrophoresis: A Low Cost Method for the Fabrication of High Performance Solution-processable Nanowire Devices at JoVE.com

Flow-assisted Dielectrophoresis: A Low Cost Method for the Fabrication of High Performance Solution-processable Nanowire Devices

本文对纳米线器件的自组装进行了流动辅助介。以硅纳米线场效应晶体管的制备为例。

流动辅助介: 一种低成本的制备高性能溶液可纳米线器件的方法

Flow-assisted dielectrophoresis (DEP) is an efficient self-assembly method for the controllable and reproducible positioning, alignment, and selection of ...

flow-assisted-dielectrophoresis-low-cost-method-for-fabrication-high

Universidad de Cartagena UDEC

Research

JoVE Journal

Engineering

7.6K 次观看.  University of Surrey. 本文对纳米线器件的自组装进行了流动辅助介。以硅纳米线场效应晶体管的制备为例。

视频: Flow-assisted Dielectrophoresis: A Low Cost Method for the Fabrication of High Performance Solution-processable Nanowire Devices

Fabricating Nanogaps by Nanoskiving

There are several methods of fabricating nanogaps with controlled spacings, but the precise control over the sub-nanometer spacing between two electrodes-and generating them in practical quantities-is still challenging. The preparation of nanogap electrodes using nanoskiving, which is a form of edge lithography, is a fast, simple and powerful technique. This method is an entirely mechanical process which does not include any photo- or electron-beam lithographic steps and does not require any special equipment or infrastructure such as clean rooms. Nanoskiving is used to fabricate electrically addressable nanogaps with control over all three dimensions; the smallest dimension of these structures is defined by the thickness of the sacrificial layer (Al or Ag) or self-assembled monolayers. These wires can be manually positioned by transporting them on drops of water and are directly electrically-addressable; no further lithography is required to connect them to an electrometer.

The fabrication of electrically addressable, high-aspect-ratio (> 1000:1) metal nanowires separated by gaps of single nanometers using either sacrificial layers of aluminum and silver or self-assembled monolayers as templates is described. These nanogap structures are fabricated without a clean room or any photo- or electron-beam lithographic processes by a form of edge lithography known as nanoskiving.

制造由Nanoskiving Nanogaps的

There are several methods of fabricating nanogaps with controlled spacings, but the precise control over the sub-nanometer spacing between two ...

科研

化学

Ultrahigh Density Array of Vertically Aligned Small-molecular Organic Nanowires on Arbitrary Substrates

In recent years &pi;-conjugated organic semiconductors have emerged as the active material in a number of diverse applications including large-area, low-cost displays, photovoltaics, printable and flexible electronics and organic spin valves. Organics allow (a) low-cost, low-temperature processing and (b) molecular-level design of electronic, optical and spin transport characteristics. Such features are not readily available for mainstream inorganic semiconductors, which have enabled organics to carve a niche in the silicon-dominated electronics market. The first generation of organic-based devices has focused on thin film geometries, grown by physical vapor deposition or solution processing. However, it has been realized that organic nanostructures can be used to enhance performance of above-mentioned applications and significant effort has been invested in exploring methods for organic nanostructure fabrication.	
A particularly interesting class of organic nanostructures is the one in which vertically oriented organic nanowires, nanorods or nanotubes are organized in a well-regimented, high-density array. Such structures are highly versatile and are ideal morphological architectures for various applications such as chemical sensors, split-dipole nanoantennas, photovoltaic devices with radially heterostructured "core-shell" nanowires, and memory devices with a cross-point geometry. Such architecture is generally realized by a template-directed approach. In the past this method has been used to grow metal and inorganic semiconductor nanowire arrays. More recently &pi;-conjugated polymer nanowires have been grown within nanoporous templates. However, these approaches have had limited success in growing nanowires of technologically important &pi;-conjugated small molecular weight organics, such as tris-8-hydroxyquinoline aluminum (Alq3), rubrene and methanofullerenes, which are commonly used in diverse areas including organic displays, photovoltaics, thin film transistors and spintronics.	
Recently we have been able to address the above-mentioned issue by employing a novel "centrifugation-assisted" approach. This method therefore broadens the spectrum of organic materials that can be patterned in a vertically ordered nanowire array. Due to the technological importance of Alq3, rubrene and methanofullerenes, our method can be used to explore how the nanostructuring of these materials affects the performance of aforementioned organic devices. The purpose of this article is to describe the technical details of the above-mentioned protocol, demonstrate how this process can be extended to grow small-molecular organic nanowires on arbitrary substrates and finally, to discuss the critical steps, limitations, possible modifications, trouble-shooting and future applications.

We report a simple method for fabricating an ultrahigh density array of vertically ordered small-molecular organic nanowires. This method allows for synthesis of complex heterostructured hybrid nanowire geometries, which can be inexpensively grown on arbitrary substrates. These structures have potential applications in organic electronics, optoelectronics, chemical sensing, photovoltaics and spintronics.

超高密度垂直对齐的任意基质的小分子有机纳米线阵列

In  recent years &pi;-conjugated  organic semiconductors have emerged as the active material in a number of  diverse applications including large-area, ...

工程学

Monolayer Contact Doping of Silicon Surfaces and Nanowires Using Organophosphorus Compounds

Monolayer Contact Doping (MLCD) is a simple method for doping of surfaces and nanostructures1. MLCD results in the formation of highly controlled, ultra shallow and sharp doping profiles at the nanometer scale. In MLCD process the dopant source is a monolayer containing dopant atoms.
In this article a detailed procedure for surface doping of silicon substrate as well as silicon nanowires is demonstrated. Phosphorus dopant source was formed using tetraethyl methylenediphosphonate monolayer on a silicon substrate. This monolayer containing substrate was brought to contact with a pristine intrinsic silicon target substrate and annealed while in contact. Sheet resistance of the target substrate was measured using 4 point probe. Intrinsic silicon nanowires were synthesized by chemical vapor deposition (CVD) process using a vapor-liquid-solid (VLS) mechanism; gold nanoparticles were used as catalyst for nanowire growth. The nanowires were suspended in ethanol by mild sonication. This suspension was used to dropcast the nanowires on silicon substrate with a silicon nitride dielectric top layer. These nanowires were doped with phosphorus in similar manner as used for the intrinsic silicon wafer. Standard photolithography process was used to fabricate metal electrodes for the formation of nanowire based field effect transistor (NW-FET). The electrical properties of a representative nanowire device were measured by a semiconductor device analyzer and a probe station.

A detailed procedure for surface doping of Silicon interfaces is provided. The ultra-shallow surface doping is demonstrated by using phosphorus containing monolayers and rapid annealing process. The method can be used for doping of macroscopic area surfaces as well as nanostructures.

Monolayer Contact Doping (MLCD) is a simple method for doping of surfaces and nanostructures1. MLCD results in the formation of highly controlled, ultra ...

Evaluating Plasmonic Transport in Current-carrying Silver Nanowires

Plasmonics is an emerging technology capable of simultaneously transporting a plasmonic signal and an electronic signal on the same information support1,2,3. In this context, metal nanowires are especially desirable for realizing dense routing networks4. A prerequisite to operate such shared nanowire-based platform relies on our ability to electrically contact individual metal nanowires and efficiently excite surface plasmon polaritons5 in this information support. In this article, we describe a protocol to bring electrical terminals to chemically-synthesized silver nanowires6 randomly distributed on a glass substrate7. The positions of the nanowire ends with respect to predefined landmarks are precisely located using standard optical transmission microscopy before encapsulation in an electron-sensitive resist. Trenches representing the electrode layout are subsequently designed by electron-beam lithography. Metal electrodes are then fabricated by thermally evaporating a Cr/Au layer followed by a chemical lift-off. The contacted silver nanowires are finally transferred to a leakage radiation microscope for surface plasmon excitation and characterization8,9. Surface plasmons are launched in the nanowires by focusing a near infrared laser beam on a diffraction-limited spot overlapping one nanowire extremity5,9. For sufficiently large nanowires, the surface plasmon mode leaks into the glass substrate9,10. This leakage radiation is readily detected, imaged, and analyzed in the different conjugate planes in leakage radiation microscopy9,11. The electrical terminals do not affect the plasmon propagation. However, a current-induced morphological deterioration of the nanowire drastically degrades the flow of surface plasmons. The combination of surface plasmon leakage radiation microscopy with a simultaneous analysis of the nanowire electrical transport characteristics reveals the intrinsic limitations of such plasmonic circuitry.

Silver nanowires can simultaneously transport electrons and optical information in the form of surface plasmons. A procedure is described here to realize such a shared circuitry and the limitations at propagating both information carriers are evaluated.

Plasmonics is an emerging technology capable of simultaneously transporting a plasmonic signal and an electronic signal on the same information ...

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 ...

生物工程

Creating Sub-50 Nm Nanofluidic Junctions in PDMS Microfluidic Chip via Self-Assembly Process of Colloidal Particles

Polydimethylsiloxane (PDMS) is the prevailing building material to make microfluidic devices due to its ease of molding and bonding as well as its transparency. Due to the softness of the PDMS material, however, it is challenging to use PDMS for building nanochannels. The channels tend to collapse easily during plasma bonding. In this paper, we present an evaporation-driven self-assembly method of silica colloidal nanoparticles to create nanofluidic junctions with sub-50 nm pores between two microchannels. The pore size as well as the surface charge of the nanofluidic junction is tunable simply by changing the colloidal silica bead size and surface functionalization outside of the assembled microfluidic device in a vial before the self-assembly process. Using the self-assembly of nanoparticles with a bead size of 300 nm, 500 nm, and 900 nm, it was possible to fabricate a porous membrane with a pore size of ~45 nm, ~75 nm and ~135 nm, respectively. Under electrical potential, this nanoporous membrane initiated ion concentration polarization (ICP) acting as a cation-selective membrane to concentrate DNA by ~1,700 times within 15 min. This non-lithographic nanofabrication process opens up a new opportunity to build a tunable nanofluidic junction for the study of nanoscale transport processes of ions and molecules inside a PDMS microfluidic chip.

We propose a simple self-assembly technique of silica colloidal nanoparticles to create a nanofluidic junction between two microchannels in polydimethylsiloxane (PDMS). Using this technique, a nanoporous bead membrane with a pore size down to ~45 nm was built inside a microchannel and applied to electrokinetic preconcentration of DNA samples.

通过胶体粒子自组装过程创建在PDMS微流控芯片分50纳米的纳米流体结

Polydimethylsiloxane (PDMS) is the prevailing building material to make microfluidic devices due to its ease of molding and bonding as well as its ...

Fabrication of Fully Solution Processed Inorganic Nanocrystal Photovoltaic Devices

We demonstrate a method for the preparation of fully solution processed inorganic solar cells from a spin and spray coating deposition of nanocrystal inks. For the photoactive absorber layer, colloidal CdTe and CdSe nanocrystals (3-5 nm) are synthesized using an inert hot injection technique and cleaned with precipitations to remove excess starting reagents. Similarly, gold nanocrystals (3-5 nm) are synthesized under ambient conditions and dissolved in organic solvents. In addition, precursor solutions for transparent conductive indium tin oxide (ITO) films are prepared from solutions of indium and tin salts paired with a reactive oxidizer. Layer-by-layer, these solutions are deposited onto a glass substrate following annealing (200-400 &#176;C) to build the nanocrystal solar cell (glass/ITO/CdSe/CdTe/Au). Pre-annealing ligand exchange is required for CdSe and CdTe nanocrystals where films are dipped in NH4Cl:methanol to replace long-chain native ligands with small inorganic Cl- anions. NH4Cl(s) was found to act as a catalyst for the sintering reaction (as a non-toxic alternative to the conventional CdCl2(s) treatment) leading to grain growth (136&#177;39 nm) during heating. The thickness and roughness of the prepared films are characterized with SEM and optical profilometry. FTIR is used to determine the degree of ligand exchange prior to sintering, and XRD is used to verify the crystallinity and phase of each material. UV/Vis spectra show high visible light transmission through the ITO layer and a red shift in the absorbance of the cadmium chalcogenide nanocrystals after thermal annealing. Current-voltage curves of completed devices are measured under simulated one sun illumination. Small differences in deposition techniques and reagents employed during ligand exchange have been shown to have a profound influence on the device properties. Here, we examine the effects of chemical (sintering and ligand exchange agents) and physical treatments (solution concentration, spray-pressure, annealing time and annealing temperature) on photovoltaic device performance.

This protocol describes the synthesis and solution deposition of inorganic nanocrystals layer by layer to produce thin film electronics on non-conductive surfaces. Solvent-stabilized inks can produce complete photovoltaic devices on glass substrates via spin and spray coating following post-deposition ligand exchange and sintering.

全面解决方案处理的无机纳米晶体光伏器件的制造

We demonstrate a method for the preparation of fully solution processed inorganic solar cells from a spin and spray coating deposition of nanocrystal ...

Electric-field Control of Electronic States in WS2 Nanodevices by Electrolyte Gating

A method of carrier number control by electrolyte gating is demonstrated. We have obtained WS2 thin flakes with atomically flat surface via scotch tape method or individual WS2 nanotubes by dispersing the suspension of WS2 nanotubes. The selected samples have been fabricated into devices by the use of the electron beam lithography and electrolyte is put on the devices. We have characterized the electronic properties of the devices under applying the gate voltage. In the small gate voltage region, ions in the electrolyte are accumulated on the surface of the samples which leads to the large electric potential drop and resultant electrostatic carrier doping at the interface. Ambipolar transfer curve has been observed in this electrostatic doping region. When the gate voltage is further increased, we met another drastic increase of source-drain current which implies that ions are intercalated into layers of WS2 and electrochemical carrier doping is realized. In such electrochemical doping region, superconductivity has been observed. The focused technique provides a powerful strategy for achieving the electric-filed-induced quantum phase transition.

Electric-field Control of Electronic States in WS2 Nanodevices by Electrolyte Gating

Here, we present a protocol to control the carrier number in solids by using the electrolyte.

用电解质浇注法对 WS2纳米器件电子态的电场控制

A method of carrier number control by electrolyte gating is demonstrated. We have obtained WS2 thin flakes with atomically flat surface via scotch tape ...

A Standard and Reliable Method to Fabricate Two-Dimensional Nanoelectronics

Two-dimensional (2D) materials have attracted huge attention due to their unique properties and potential applications. Since wafer scale synthesis of 2D materials is still in nascent stages, scientists cannot fully rely on traditional semiconductor techniques for related research. Delicate processes from locating the materials to electrode definition need to be well controlled. In this article, a universal fabrication protocol required in manufacturing nanoscale electronics, such as 2D quasi-heterojunction bipolar transistors (Q-HBT), and 2D back-gated transistors are demonstrated. This protocol includes the determination of material position, electron beam lithography (EBL), metal electrode definition, et al. A step by step narrative of the fabrication procedures for these devices are also presented. Furthermore, results show that each of the fabricated devices has achieved high performance with high repeatability. This work reveals a comprehensive description of process flow for preparing 2D nano-electronics, enables the research groups to access this information, and pave the way toward future electronics.

The article aims to introduce a standard and reliable fabrication procedure for the development of future low dimensional nanoelectronics.

制造二维电子学的标准可靠方法

Two-dimensional (2D) materials have attracted huge attention due to their unique properties and potential applications. Since wafer scale synthesis of 2D ...

Iron Nanowire Fabrication by Nano-Porous Anodized Aluminum and its Characterization

Magnetic nanowires possess unique properties that have attracted the interest of different fields of research, including basic physics, biomedicine, and data storage. We demonstrate a fabrication method for iron (Fe) nanowires&#160;via electrochemical deposition into anodic&#160;alumina oxide (AAO) templates. The templates are fabricated by anodization of aluminum (Al) discs, and the pore length and diameter are controlled by changing the anodizing conditions. Pores with an average diameter of around 120 nm are created using oxalic acid as the electrolyte. Using this method, cylindrical nanowires are synthesized, which are released by dissolving the alumina using a selective chemical etchant.

In this work, we describe a&#160;protocol to fabricate iron nanowires, including the formation of the porous alumina membrane that is used as the template, electrodeposition into templates using electrolyte solution, and the release of the nanowires into the solution.

纳米孔阳极氧化铝的铁纳米线制造及其特性

Magnetic nanowires possess unique properties that have attracted the interest of different fields of research, including basic physics, biomedicine, and ...