Name: seedless growth of bismuth nanowire array via vacuum thermal evaporation
Uploaded: 2015-12-21T13:00:00.000+00:00
Duration: 8 min 58 s
Description: Watch this Scientific Journal Video about Seedless Growth of Bismuth Nanowire Array via Vacuum Thermal Evaporation at JoVE.com

Research is carried out at the Center for Functional Nanomaterials, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-SC0012704.

注意:使用前请咨询所有相关的材料安全数据表（MSDS）。相比，他们的大部分对手纳米材料可能有额外的危险。处理纳米材料覆盖的基板时，包括利用工程控制（通风柜）和个人防护装备的请使用一切适当的安全措施（安全眼镜，手套，实验室外套，全长长裤，闭趾鞋）。 1.准备工作<ol><li>气相沉积系统的制备<ol><li>泄沉积室到大气压力，并打开该室。排空是通过按压控制软件接口，它自动开始的序列泄腔室向大气压力的"启动PC放空"按钮来完成。在达到大气压拉动前访问门打开密室。 </li><li>一对热蒸发电极之间挂载的钨蒸发舟（氧化铝涂层）。将1摹铋颗粒进入蒸发舟。 </li><li>装入钒溅射靶的磁控管溅射源。参照步骤1.1.4）为没有配备有溅射源沉积系统。 </li><li> （ 可选的，为没有配备有溅射源沉积系统 ）安装的一对热蒸发电极之间的钨蒸发舟。将0.5克钒蛞蝓进入蒸发舟。 </li><li>闭环温度控制器的微型香蕉连接器（两个用于加热/冷却功率，两个用于温度探头）连接到淀积系统的电馈通。 </li></ol></li><li>生长基质制备 注意:铋纳米线的形成是不敏感的选择的生长衬底。类似的结果已经从载玻片，硅晶片，或金属片获得的。建议由衬底进行清洁之前立即蒸气的作者沉积过程中，为了达到钒垫层的一个一致的附着力。各种衬底清洗技术，包括等离子体清洗和湿化学清洗，可以应用并导致类似的结果。 <ol><li>清洁生长基质由氧等离子体<ol><li>将生长基质成等离子体清洁器和泵腔室，通过按"VAC ON"键，以10毫乇其基本压力。 </li><li>打开氧气阀和通过按"GAS ON"键面板上引入氧气至腔室并通过按下"INCR"和"DECR"按钮，用于气体流量控制，以保持腔室压力调节流量约100毫乇。 </li><li>通过按下"INCR"和"DECR"按钮用于功率控制设置等离子体功率在20瓦，并按下"RF ON"按钮点燃等离子体。 </li><li>关闭血浆按前等待5分钟"的RF开"。按钮放空室通过按"BLEED"按钮，检索衬底。 </li></ol></li><li>清洁生长基质通过湿化学法<ol><li>浸入包含在一个烧杯中丙酮的生长衬底。将烧杯到超声发生器和超声处理2分钟，在最大功率。 </li><li>从烧杯中取出基片，并与无水乙醇从洗瓶30秒的流冲洗。 </li><li>干燥基板在氮气气流。 </li></ol></li></ol></li><li>衬底装载和沉积系统抽<ol><li>将基板温度控制组件贴装到衬底支架。 </li><li>使用弹簧夹装入生长基质上的珀耳帖冷却器/加热器组件的顶部。 </li><li>完全组装的衬底保持器安装到蒸镀室，与面对淀积源的衬底。连接电馈送到佩尔蒂埃冷却器/加热器组件。 </li><li>关闭衬底挡板，以避免无意的沉积在基底上。 </li><li>启动抽真空沉积室中。泵送通过按下控制软件接口，它自动开始的序列泵室向它的基本压力"开始的PC泵送"按钮来完成。 </li></ol></li></ol> 2.成长铋纳米线注意:实验不移动到下一步骤，直至淀积室的底部压力达到2×10 -6乇或更低。 <ol><li>钒底层的沉积 注意:当钒垫层由磁控管溅射法淀积的最佳实验的再现性得以实现。在没有溅射源的，高重复性也可以仍然通过使用热蒸发法沉积钒垫层实现的，条件是该沉积系统公顷SA基数较低压力（≤5×10 -7托）。参照步骤3.1.2细节。 <ol><li>钒沉积用的磁控管溅射源。 <ol><li>开始在溅射源氩气流。设置流速为40 SCCM。 </li><li>调整涡轮分子泵的转速为2.5毫托的室压。 </li><li>虽然腔逐渐达到其稳定状态的压力，设置厚度校准因素对QCM。为钒，密度为5.96克/厘米3以及Z因子是0.530。 </li><li>打开DC溅射源，并设置在功率200-250 W的由作者操作的沉积系统，所述沉积速率为约0.4埃/秒，在此功率。无需打开衬底快门，保持源运行2分钟。 注:通过本步骤的钒源的天然氧化物除去，露出新鲜钒表面。 </li><li>打开基板快门启动钒沉积物等ñ。在此期间，重置QCM的累积厚度为零。 </li><li>继续沉积直到20nm的表观厚度累积，每QCM读数。关闭基板快门。 </li><li>逐渐减小溅射功率到零。关闭播放源。 </li><li>关闭氩气流。返回涡轮分子泵以充分发挥其威力。 </li></ol></li><li> （ 可选的，为没有配备有溅射源沉积系统 ）钒沉积与热蒸发源。 <ol><li>由于钒的熔点高（1910 ℃）和它准备氧化，所以建议以在5×10 -7乇或更低的基础压力下进行其热蒸发。 </li><li>设置厚度校准因素对QCM。为钒，密度为5.96克/厘米3以及Z因子是0.530。 </li><li>打开热蒸发电源到钒源。缓慢增加加热功率的钨舟，直到钒蛞蝓融化。 </li><li>与基板快门保持关闭，慢慢增加加热功率直到2埃/秒的沉积速率达到，每QCM读数。打开基板快门启动钒沉积。在此期间，重置QCM的累积厚度为零。 </li><li>继续沉积直到50nm的表观厚度被积累。关闭基板快门。 </li><li>逐渐减小热蒸发功率到零。关闭播放源。 </li></ol></li></ol></li><li>铋纳米线的沉积<ol><li>铋沉积在温度高于或低于室温，设置所需的值到温度控制器。等待，直到所需的温度为止。 </li><li>设置厚度校准因素对QCM。为铋，密度为9.78克/厘米3以及Z因子是0.790。 </li><li>打开热蒸发功率苏pply到铋源。慢慢增加加热功率的钨舟直到2埃/秒的沉积速率来实​​现，每QCM读数。 </li><li>打开基板快门启动铋沉积。在此期间，重置QCM的累积厚度为零。 </li><li>继续沉积直到50nm的表观厚度被积累。关闭基板快门。 </li><li>逐渐减小热蒸发功率到零。关闭播放源。 </li><li>关掉电源到热电冷却器/加热器。 </li><li>泄沉积室到大气压力，并打开该室。检索衬底支架和收集铋纳米线覆盖衬底。 </li></ol></li></ol>

<ol>
	<li>Hu, J. T., Odom, T. W., Lieber, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemistry+and+physics+in+one+dimension:+Synthesis+and+properties+of+nanowires+and+nanotubes.">Chemistry and physics in one dimension: Synthesis and properties of nanowires and nanotubes.</a> Acc. Chem. Res. 32, 435-445 (1999).</li><li>Akimov, A. V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Generation+of+single+optical+plasmons+in+metallic+nanowires+coupled+to+quantum+dots.">Generation of single optical plasmons in metallic nanowires coupled to quantum dots.</a> Nature. 450, 402-406 (2007).</li><li>Thurn-Albrecht, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrahigh-density+nanowire+arrays+grown+in+self-assembled+diblock+copolymer+templates.">Ultrahigh-density nanowire arrays grown in self-assembled diblock copolymer templates.</a> Science. 290, 2126-2129 (2000).</li><li>Xia, Y. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=One-dimensional+nanostructures:+Synthesis,+characterization,+and+applications.">One-dimensional nanostructures: Synthesis, characterization, and applications.</a> Adv. Mater. 15, 353-389 (2003).</li><li>Gudiksen, M. S., Lauhon, L. J., Wang, J., Smith, D. C., Lieber, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth+of+nanowire+superlattice+structures+for+nanoscale+photonics+and+electronics.">Growth of nanowire superlattice structures for nanoscale photonics and electronics.</a> Nature. 415, 617-620 (2002).</li><li>Yang, P. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlled+growth+of+ZnO+nanowires+and+their+optical+properties.">Controlled growth of ZnO nanowires and their optical properties.</a> Adv. Funct. Mater. 12, 323-331 (2002).</li><li>Allen, J. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-resolution+detection+of+Au+catalyst+atoms+in+Si+nanowires.">High-resolution detection of Au catalyst atoms in Si nanowires.</a> Nature Nanotech. 3, 168-173 (2008).</li><li>Lin, Y. M., Sun, X. Z., Dresselhaus, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Theoretical+investigation+of+thermoelectric+transport+properties+of+cylindrical+Bi+nanowires.">Theoretical investigation of thermoelectric transport properties of cylindrical Bi nanowires.</a> Phys. Rev. B. 62, 4610-4623 (2000).</li><li>Isaacson, R. T., Williams, G. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alfv&#233;n-Wave+propagation+in+solid-state+plasmas.+III.+Quantum+oscillations+of+the+Fermi+surface+of+bismuth.">Alfv&#233;n-Wave propagation in solid-state plasmas. III. Quantum oscillations of the Fermi surface of bismuth.</a> Phys Rev. 185, 682-688 (1969).</li><li>Sandomirskii, V. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantum+size+effect+in+a+semimetal+film.">Quantum size effect in a semimetal film.</a> Sov. Phys. JETP. 25, 101-106 (1967).</li><li>Huber, T. E., Nikolaeva, A., Gitsu, D., Konopko, L., Graf, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantum+confinement+and+surface-state+effects+in+bismuth+nanowires.">Quantum confinement and surface-state effects in bismuth nanowires.</a> Physica E. 37, 194-199 (2007).</li><li>Black, M. R., Lin, Y. M., Cronin, S. B., Rabin, O., Dresselhaus, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Infrared+absorption+in+bismuth+nanowires+resulting+from+quantum+confinement.">Infrared absorption in bismuth nanowires resulting from quantum confinement.</a> Phys. Rev. B. 65, 2921-2930 (2002).</li><li>Hofmann, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+surfaces+of+bismuth:+Structural+and+electronic+properties.">The surfaces of bismuth: Structural and electronic properties.</a> Prog. Surf. Sci. 81, 191-245 (2006).</li><li>Huber, T. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Confinement+effects+and+surface-induced+charge+carriers+in+Bi+quantum+wires.">Confinement effects and surface-induced charge carriers in Bi quantum wires.</a> Appl Phys Lett. 84, 1326-1328 (2004).</li><li>Huber, T. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+state+band+mobility+and+thermopower+in+semiconducting+bismuth+nanowires.">Surface state band mobility and thermopower in semiconducting bismuth nanowires.</a> Phys. Rev. B. 83, 235414-23 (2011).</li><li>Dresselhaus, M. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> 23, 129-140 (2003).</li><li>Cheng, Y. -. T., Weiner, A. M., Wong, C. A., Balogh, M. P., Lukitsch, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stress-induced+growth+of+bismuth+nanowires.">Stress-induced growth of bismuth nanowires.</a> Appl Phys Lett. 81, 3248-3250 (2002).</li><li>Volobuev, V. V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+mechanism+of+Bi+nanowire+growth+from+Bi/Co+immiscible+composite+thin+films.">The mechanism of Bi nanowire growth from Bi/Co immiscible composite thin films.</a> J. Nanosci. Nanotech. 12, 8624-8629 (2012).</li><li>Shim, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On-film+formation+of+Bi+nanowires+with+extraordinary+electron+mobility.">On-film formation of Bi nanowires with extraordinary electron mobility.</a> Nano Lett. 9, 18-22 (2009).</li><li>Berglund, S. P., Rettie, A. J. E., Hoang, S., Mullins, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Incorporation+of+Mo+and+W+into+nanostructured+BiVO4+films+for+efficient+photoelectrochemical+water+oxidation.">Incorporation of Mo and W into nanostructured BiVO4 films for efficient photoelectrochemical water oxidation.</a> Phys. Chem. Chem. Phys. 14, 7065-7075 (2012).</li><li>Liu, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface-Energy+Induced+Formation+of+Single+Crystalline+Bismuth+Nanowires+over+Vanadium+Thin+Film+at+Room+Temperature.">Surface-Energy Induced Formation of Single Crystalline Bismuth Nanowires over Vanadium Thin Film at Room Temperature.</a> Nano Lett. 14, 5630-5635 (2014).</li></ol>

Authors have nothing to disclose.

铋纳米线的生长是要在物理气相沉积系统具有至少两个沉积源，一个用于铋，另一个用于钒进行的。所以建议的来源之一是一个磁控管溅射源，钒的沉积。高真空是通过干式涡旋泵的支持一个分子泵实现。的气相沉积系统， 在原地膜厚监控配备校准的石英晶体微天平（QCM）为。的气相沉积系统具有电馈送对于生长衬底闭环温度控制。热电温度控制器提供加热/冷却到衬底上，通过被热粘合?...

纳米线限制电荷载体和其他的准粒子，诸如光子和等离子体的传输在一个方面。因此，纳米线通常表现新颖的电，磁，光，化学性能，这对于微/纳米电子学，光子学，生物医学，环境和能源相关技术的应用赋予他们几乎无限的潜力。1,2在过去的二十年中，无数顶向下和自底向上方法已经发展到合成各种高品质的金属或半导体纳米线的在实验室规模3-6尽管这些进展，每一种方法依赖于对于其成功的最终产品的某些独特性质。例如，流行的气-液-固（VLS）的方法是更适合用于具有较高的熔点，并与相应的催化"种子"形成共晶合金。7作为结果，半导体材料，纳米线的合成特别令人感兴趣的材料可能不被包括在现有的技术。 作为一种半金属小间接带重叠（-38兆电子伏在0 K）和不寻常的光电荷载体，铋就是这样一个例子。相比，其体积的材料表现在降低的尺寸完全不同，因为量子约束可以把铋纳米线或薄膜成窄带隙半导体8-12在此期间，铋形成表面上的准二维金属比其体积显著多种金属。13,14-结果表明铋的表面达到2×10 4厘米2 V -1 秒 -1的电子迁移率和强烈有助于其热电功率在纳米线的形式。15作为这样，有钻研铋纳米线为电子，特别热电应用显著利益12-16然而，由于铋的非常低的熔点（544 K）和准备用于氧化，但仍然为合成高品质和使用传统的汽相或溶液相技术单晶铋纳米线是一个挑战。 此前，已经报道由几组，在铋薄膜，这是由于应力的内置于膜中的释放的真空沉积单晶铋纳米线生长在低收率17-20最近，我们发现了一种新技术，它是基于在高真空下铋的热蒸发，并导致高收率可伸缩形成单晶铋纳米线。21相较于先前报道的方法，该技术的最独特的特征是，在生长衬底是新鲜涂覆有一层薄薄的铋沉积之前纳米多孔钒。在后者的热蒸发，铋蒸汽渗透到车的纳米多孔结构Adium的电影和凝结那里作为纳米畴。因为钒未被冷凝的铋润湿，渗透的域随后从钒矩阵逐出释放其表面能。它是铋纳米畴形成垂直铋纳米线的连续驱逐。由于铋域只有1-2纳米的直径，他们是受显著熔点抑制，这使得他们几乎熔化在室温。其结果是，纳米线的生长与在室温保持的基板进行。另一方面，作为铋畴的迁移被热激活时，纳米线的长度和宽度，可以通过简单地控制生长衬底的温度调谐在宽范围内。该详细视频协议的目的是帮助新从业人员在实地避免与薄膜中的高真空，无氧的环境中的物理汽相沉积相关联的各种常见的问题。

<table><tbody><tr><td>Bismuth</td><td>Sigma-Aldrich</td><td>556130</td><td>Granular, 99.999%</td></tr><tr><td>Vanadium Slug</td><td>Alfa Aesar</td><td>42829</td><td>3.175&amp;nbsp;mm (0.125&amp;nbsp;in) dia x 6.35&amp;nbsp;mm (0.25&amp;nbsp;in) length, 99.8%</td></tr><tr><td>Vanadium Sputtering Target</td><td>Kurt J. Lesker</td><td>EJTVXXX253A2</td><td>3.00&quot; Dia. x 0.125&quot; Thick, 99.5%</td></tr><tr><td>Acetone</td><td>Sigma-Aldrich</td><td>179124</td><td>&gt;99.5%</td></tr><tr><td>Ethanol</td><td>Alfa Aesar</td><td>33361</td><td>Anhydrous</td></tr><tr><td>Silicon Wafer</td><td>University Wafers</td><td></td><td>300 microns in thickness, (100) orientation</td></tr><tr><td>Silver Filled Epoxy</td><td>Circuit Works</td><td>CW2400</td><td>Two part conductive epoxy resin</td></tr><tr><td>Tungsten Boat, Alumina Coated</td><td>R. D. Mathis</td><td>S9B-AO-W</td><td>For bismuth thermal evaporation</td></tr><tr><td>Tungsten Boat</td><td>R. D. Mathis</td><td>S4-.015W</td><td>For vanadium thermal evaporation</td></tr><tr><td>RIE Plasma</td><td>Nordson March</td><td>CS-1701</td><td></td></tr><tr><td>PVD 75 Vapor Deposition Platform</td><td>Kurt J. Lesker</td><td>PEDP75FTCLT001</td><td>Equipped with three thermal evaporation source and one DC magnetron sputtering source</td></tr><tr><td>Thermoelectric Temperature Controller</td><td>LairdTech</td><td>MTTC-1410</td><td></td></tr><tr><td>PT1000 RGD</td><td>LairdTech</td><td>340912-01</td><td>Temperature sensor for MTTC-1410</td></tr><tr><td>Thermoelectric Module</td><td>LairdTech</td><td>56910-502</td><td></td></tr><tr><td>Ultrasonicator</td><td>Crest Ultrasonics</td><td>Tru-Sweep 175</td><td></td></tr></tbody></table>

seedless growth of bismuth nanowire array via vacuum thermal evaporation

这里一个无籽和无模板技术被证明可伸缩在高真空中在RT生长铋纳米线，通过热蒸发。为金属薄膜，热蒸发沉积的制造铋成垂直单晶纳米线以上的钒在室温保持一个平坦的薄膜，这是新鲜的磁控溅射或热蒸发沉积的阵列通常保留。通过控制生长衬底的温度的纳米线的长度和宽度可以调节在宽范围内。负责这种新颖的技术是一种以前未知的纳米线生长机理，在钒薄膜的孔隙率温和根。渗入毛孔钒，铋域（约1纳米）进行过度的表面能，抑制它们的熔点，不断驱逐出来的钒基体形成纳米线。这一发现证明了可扩展的气相合成器的可行性高纯度纳米材料ESIS不使用任何催化剂。

通过磁控溅射和热蒸发方法形成的钒底层的横截面SEM图像示于图2。扫描电子显微镜（SEM）图像呈现为形成在不同的衬底温度铋纳米线（图3）。该晶体的铋纳米线结构是通过透射电子显微镜（TEM），选择区域电子衍射（SAED），和X射线衍射（XRD）研究（ 图4）来确定。通过能量色散X射线光谱仪的元素分析表明，铋纳米线未 ​​合金化的钒底层（ <s...

Watch this Scientific Journal Video about Seedless Growth of Bismuth Nanowire Array via Vacuum Thermal Evaporation at JoVE.com

Seedless Growth of Bismuth Nanowire Array via Vacuum Thermal Evaporation

A protocol for seedless and high yield growth of bismuth nanowire arrays through vacuum thermal evaporation technique is presented.

铋纳米线阵列通过真空热蒸发无核增长

Here a seedless and template-free technique is demonstrated to scalably grow bismuth nanowires, through thermal evaporation in high vacuum at RT. ...

seedless-growth-bismuth-nanowire-array-via-vacuum-thermal

Universidad San Sebastian

Research

JoVE Journal

Engineering

8.3K 次观看.  Brookhaven National Laboratory. A protocol for seedless and high yield growth of bismuth nanowire arrays through vacuum thermal evaporation technique is presented. 

视频: Seedless Growth of Bismuth Nanowire Array via Vacuum Thermal Evaporation

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

Dry Oxidation and Vacuum Annealing Treatments for Tuning the Wetting Properties of Carbon Nanotube Arrays

In this article, we describe a simple method to reversibly tune the wetting properties of vertically aligned carbon nanotube (CNT) arrays. Here, CNT arrays are defined as densely packed multi-walled carbon nanotubes oriented perpendicular to the growth substrate as a result of a growth process by the standard thermal chemical vapor deposition (CVD) technique.1,2 These CNT arrays are then exposed to vacuum annealing treatment to make them more hydrophobic or to dry oxidation treatment to render them more hydrophilic. The hydrophobic CNT arrays can be turned hydrophilic by exposing them to dry oxidation treatment, while the hydrophilic CNT arrays can be turned hydrophobic by exposing them to vacuum annealing treatment. Using a combination of both treatments, CNT arrays can be repeatedly switched between hydrophilic and hydrophobic.2 Therefore, such combination show a very high potential in many industrial and consumer applications, including drug delivery system and high power density supercapacitors.3-5
The key to vary the wettability of CNT arrays is to control the surface concentration of oxygen adsorbates. Basically oxygen adsorbates can be introduced by exposing the CNT arrays to any oxidation treatment. Here we use dry oxidation treatments, such as oxygen plasma and UV/ozone, to functionalize the surface of CNT with oxygenated functional groups. These oxygenated functional groups allow hydrogen bond between the surface of CNT and water molecules to form, rendering the CNT hydrophilic. To turn them hydrophobic, adsorbed oxygen must be removed from the surface of CNT. Here we employ vacuum annealing treatment to induce oxygen desorption process. CNT arrays with extremely low surface concentration of oxygen adsorbates exhibit a superhydrophobic behavior.

This article describes a simple method to fabricate vertically aligned carbon nanotube arrays by CVD and to subsequently tune their wetting properties by exposing them to vacuum annealing or dry oxidation treatment.

干式氧化及真空退火处理调整的润湿性能的碳纳米管阵列

In this article, we describe a simple method to reversibly  tune the wetting properties of vertically aligned carbon nanotube (CNT) arrays.  Here, CNT ...

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, ...

Analysis of Contact Interfaces for Single GaN Nanowire Devices

Single GaN nanowire (NW) devices fabricated on SiO2 can exhibit a strong degradation after annealing due to the occurrence of void formation at the contact/SiO2 interface. This void formation can cause cracking and delamination of the metal film, which can increase the resistance or lead to a complete failure of the NW device. In order to address issues associated with void formation, a technique was developed that removes Ni/Au contact metal films from the substrates to allow for the examination and characterization of the contact/substrate and contact/NW interfaces of single GaN NW devices. This procedure determines the degree of adhesion of the contact films to the substrate and NWs and allows for the characterization of the morphology and composition of the contact interface with the substrate and nanowires. This technique is also useful for assessing the amount of residual contamination that remains from the NW suspension and from photolithographic processes on the NW-SiO2 surface prior to metal deposition. The detailed steps of this procedure are presented for the removal of annealed Ni/Au contacts to Mg-doped GaN NWs on a SiO2 substrate.

A technique was developed that removes Ni/Au contact metal films from their substrate to allow for the examination and characterization of the contact/substrate and contact/NW interfaces of single GaN nanowire devices.

单氮化镓纳米线设备分析接触界面

Single GaN nanowire (NW) devices fabricated on SiO2 can exhibit  a strong degradation after annealing due to the  occurrence of void formation at the ...

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 ...

Atomically Defined Templates for Epitaxial Growth of Complex Oxide Thin Films

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain such surfaces are described. The first approach is the preparation of single terminated perovskite SrTiO3 (001) and DyScO3 (110) substrates. Wet etching was used to selectively remove one of the two possible surface terminations, while an annealing step was used to increase the smoothness of the surface. The resulting single terminated surfaces allow for the heteroepitaxial growth of perovskite oxide thin films with high crystalline quality and well-defined interfaces between substrate and film. In the second approach, seed layers for epitaxial film growth on arbitrary substrates were created by Langmuir-Blodgett (LB) deposition of nanosheets. As model system Ca2Nb3O10- nanosheets were used, prepared by delamination of their layered parent compound HCa2Nb3O10. A key advantage of creating seed layers with nanosheets is that relatively expensive and size-limited single crystalline substrates can be replaced by virtually any substrate material.

Various procedures are outlined to prepare atomically defined templates for epitaxial growth of complex oxide thin films. Chemical treatments of single crystalline SrTiO3 (001) and DyScO3 (110) substrates were performed to obtain atomically smooth, single terminated surfaces. Ca2 Nb3 O10- nanosheets were used to create atomically defined templates on arbitrary substrates.

原子定义模板复合氧化物薄膜的外延生长

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain ...

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 ...

生物工程

Synthesis of Substrate-Bound Au Nanowires Via an Active Surface Growth Mechanism

Advancing synthetic capabilities is important for the development of nanoscience and nanotechnology. The synthesis of nanowires has always been a challenge, as it requires asymmetric growth of symmetric crystals. Here, we report a distinctive synthesis of substrate-bound Au nanowires. This template-free synthesis employs thiolated ligands and substrate adsorption to achieve the continuous asymmetric deposition of Au in solution at ambient conditions. The thiolated ligand prevented the Au deposition on the exposed surface of the seeds, so the Au deposition only occurs at the interface between the Au seeds and the substrate. The side of the newly deposited Au nanowires is immediately covered with the thiolated ligand, while the bottom facing the substrate remains ligand-free and active for the next round of Au deposition. We further demonstrate that this Au nanowire growth can be induced on various substrates, and different thiolated ligands can be used to regulate the surface chemistry of the nanowires. The diameter of the nanowires can also be controlled with mixed ligands, in which another &#34;bad&#34; ligand could turn on the lateral growth. With the understanding of the mechanism, Au nanowire-based nanostructures can be designed and synthesized.

We report a solution-based method to synthesize substrate-bound Au nanowires. By tuning the molecular ligands used during the synthesis, the Au nanowires can be grown from various substrates with different surface properties. Au nanowire-based nanostructures can also be synthesized by adjusting the reaction parameters.

通过活性表面生长机制合成基片束缚金纳米线

Advancing synthetic capabilities is important for the development of nanoscience and nanotechnology. The synthesis of nanowires has always been a ...

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 ...

Fabrication of Schottky Diodes on Zn-polar BeMgZnO/ZnO Heterostructure Grown by Plasma-assisted Molecular Beam Epitaxy

Heterostructure field effect transistors (HFETs) utilizing a two dimensional electron gas (2DEG) channel have a great potential for high speed device applications. Zinc oxide (ZnO), a semiconductor with a wide bandgap (3.4 eV) and high electron saturation velocity has gained a great deal of attention as an attractive material for high speed devices. Efficient gate modulation, however, requires high-quality Schottky contacts on the barrier layer. In this article, we present our Schottky diode fabrication procedure on Zn-polar BeMgZnO/ZnO heterostructure with high density 2DEG which is achieved through strain modulation and incorporation of a few percent Be into the MgZnO-based barrier during growth by molecular beam epitaxy (MBE). To achieve high crystalline quality, nearly lattice-matched high-resistivity GaN templates grown by metal-organic chemical vapor deposition (MOCVD) are used as the substrate for the subsequent MBE growth of the oxide layers. To obtain the requisite Zn-polarity, careful surface treatment of GaN templates and control over the VI/II ratio during the growth of low temperature ZnO nucleation layer are utilized. Ti/Au electrodes serve as Ohmic contacts, and Ag electrodes deposited on the O2 plasma pretreated BeMgZnO surface are used for Schottky contacts.

Attainment of high-quality Schottky contacts is imperative for achieving efficient gate modulation in heterostructure field effect transistors (HFETs). We present the fabrication methodology and characteristics of Schottky diodes on Zn-polar BeMgZnO/ZnO heterostructures with high-density two dimensional electron gas (2DEG), grown by plasma-assisted molecular beam epitaxy on GaN templates.

等离子体辅助分子束外延法制备的锌极性 BeMgZnO/氧化锌异质结构肖特基二极管的制备

Heterostructure field effect transistors (HFETs) utilizing a two dimensional electron gas (2DEG) channel have a great potential for high speed device ...