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&#160;</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>3.175mm (0.125in) dia x 6.35mm (0.25in) length, 99.8%&#160;</td>
		</tr>
		<tr>
			<td>Vanadium Sputtering Target</td>
			<td>Kurt J. Lesker</td>
			<td>EJTVXXX253A2</td>
			<td>3.00&#34; Dia. x 0.125&#34; Thick, 99.5%</td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>Sigma-Aldrich</td>
			<td>179124</td>
			<td>&#62;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

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

Molecular Beam Mass Spectrometry With Tunable Vacuum Ultraviolet (VUV) Synchrotron Radiation

Tunable soft ionization coupled to mass spectroscopy is a powerful method to investigate isolated molecules, complexes and clusters and their spectroscopy and dynamics1-4. Fundamental studies of photoionization processes of biomolecules provide information about the electronic structure of these systems. Furthermore determinations of ionization energies and other properties of biomolecules in the gas phase are not trivial, and these experiments provide a platform to generate these data. We have developed a thermal vaporization technique coupled with supersonic molecular beams that provides a gentle way to transport these species into the gas phase. Judicious combination of source gas and temperature allows for formation of dimers and higher clusters of the DNA bases. The focus of this particular work is on the effects of non-covalent interactions, i.e., hydrogen bonding, stacking, and electrostatic interactions, on the ionization energies and proton transfer of individual biomolecules, their complexes and upon micro-hydration by water1, 5-9.
We have performed experimental and theoretical characterization of the photoionization dynamics of gas-phase uracil and 1,3-dimethyluracil dimers using molecular beams coupled with synchrotron radiation at the Chemical Dynamics Beamline10 located at the Advanced Light Source and the experimental details are visualized here. This allowed us to observe the proton transfer in 1,3-dimethyluracil dimers, a system with pi stacking geometry and with no hydrogen bonds1. Molecular beams provide a very convenient and efficient way to isolate the sample of interest from environmental perturbations which in return allows accurate comparison with electronic structure calculations11, 12. By tuning the photon energy from the synchrotron, a photoionization efficiency (PIE) curve can be plotted which informs us about the cationic electronic states. These values can then be compared to theoretical models and calculations and in turn, explain in detail the electronic structure and dynamics of the investigated species 1, 3.

Molecular Beam Mass Spectrometry With Tunable Vacuum Ultraviolet VUV Synchrotron Radiation

A molecular beam coupled to tunable vacuum ultraviolet photoionization mass spectrometer at a synchrotron provides a convenient tool to explore the electronic structure of isolated gas phase molecules and clusters. Proton transfer mechanisms in DNA base dimers were elucidated with this technique.

可调式真空紫外（VUV）同步辐射分子束质谱分析

Tunable soft ionization coupled to mass spectroscopy is a powerful method to investigate isolated molecules, complexes and clusters and their spectroscopy ...

科研

工程学

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 ...

Characterization of Thermal Transport in One-dimensional Solid Materials

The TET (transient electro-thermal) technique is an effective approach developed to measure the thermal diffusivity of solid materials, including conductive, semi-conductive or nonconductive one-dimensional structures. This technique broadens the measurement scope of materials (conductive and nonconductive) and improves the accuracy and stability. If the sample (especially biomaterials, such as human head hair, spider silk, and silkworm silk) is not conductive, it will be coated with a gold layer to make it electronically conductive. The effect of parasitic conduction and radiative losses on the thermal diffusivity can be subtracted during data processing. Then the real thermal conductivity can be calculated with the given value of volume-based specific heat (&#961;cp), which can be obtained from calibration, noncontact photo-thermal technique or measuring the density and specific heat separately. In this work, human head hair samples are used to show how to set up the experiment, process the experimental data, and subtract the effect of parasitic conduction and radiative losses.

The TET (transient electro-thermal) technique is an effective approach developed to measure the thermal diffusivity of solid materials.

在一维固体材料的热传输的特性

The TET (transient electro-thermal) technique is an effective approach developed to measure the thermal diffusivity of solid materials, including ...

The Preparation of Electrohydrodynamic Bridges from Polar Dielectric Liquids

Horizontal and vertical liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields (8-20 kV/cm) and polar dielectric liquids. These bridges are unique from capillary bridges in that they exhibit extensibility beyond a few millimeters, have complex bi-directional mass transfer patterns, and emit non-Planck infrared radiation. A number of common solvents can form such bridges as well as low conductivity solutions and colloidal suspensions. The macroscopic behavior is governed by electrohydrodynamics and provides a means of studying fluid flow phenomena without the presence of rigid walls. Prior to the onset of a liquid bridge several important phenomena can be observed including advancing meniscus height (electrowetting), bulk fluid circulation (the Sumoto effect), and the ejection of charged droplets (electrospray). The interaction between surface, polarization, and displacement forces can be directly examined by varying applied voltage and bridge length. The electric field, assisted by gravity, stabilizes the liquid bridge against Rayleigh-Plateau instabilities. Construction of basic apparatus for both vertical and horizontal orientation along with operational examples, including thermographic images, for three liquids (e.g., water, DMSO, and glycerol) is presented.

Horizontal and vertical electrohydrodynamic liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields and polar dielectric liquids. The construction of basic apparatus and operational examples, including thermographic images, for three liquids (e.g., water, DMSO, and glycerol) is presented.

高压直流电桥从极地介电液的制备

Horizontal and vertical liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields (8-20 kV/cm) and ...

Making Record-efficiency SnS Solar Cells by Thermal Evaporation and Atomic Layer Deposition

Tin sulfide (SnS) is a candidate absorber material for Earth-abundant, non-toxic solar cells. SnS offers easy phase control and rapid growth by congruent thermal evaporation, and it absorbs visible light strongly. However, for a long time the record power conversion efficiency of SnS solar cells remained below 2%. Recently we demonstrated new certified record efficiencies of 4.36% using SnS deposited by atomic layer deposition, and 3.88% using thermal evaporation. Here the fabrication procedure for these record solar cells is described, and the statistical distribution of the fabrication process is reported. The standard deviation of efficiency measured on a single substrate is typically over 0.5%. All steps including substrate selection and cleaning, Mo sputtering for the rear contact (cathode), SnS deposition, annealing, surface passivation, Zn(O,S) buffer layer selection and deposition, transparent conductor (anode) deposition, and metallization are described. On each substrate we fabricate 11 individual devices, each with active area 0.25 cm2. Further, a system for high throughput measurements of current-voltage curves under simulated solar light, and external quantum efficiency measurement with variable light bias is described. With this system we are able to measure full data sets on all 11 devices in an automated manner and in minimal time. These results illustrate the value of studying large sample sets, rather than focusing narrowly on the highest performing devices. Large data sets help us to distinguish and remedy individual loss mechanisms affecting our devices.

Tin sulfide (SnS) is a candidate material for Earth-abundant, non-toxic solar cells. Here, we demonstrate the fabrication procedure of the SnS solar cells employing atomic layer deposition, which yields 4.36% certified power conversion efficiency, and thermal evaporation which yields 3.88%.

通过热蒸发和原子层沉积使记录效率的SnS太阳能电池

Tin sulfide (SnS) is a candidate absorber material for Earth-abundant, non-toxic solar cells. SnS offers easy phase control and rapid growth by congruent ...

Thermal Measurement Techniques in Analytical Microfluidic Devices

Thermal measurement techniques have been used for many applications such as thermal characterization of materials and chemical reaction detection. Micromachining techniques allow reduction of the thermal mass of fabricated structures and introduce the possibility to perform high sensitivity thermal measurements in the micro-scale and nano-scale devices. Combining thermal measurement techniques with microfluidic devices allows performing different analytical measurements with low sample consumption and reduced measurement time by integrating the miniaturized system on a single chip. The procedures of thermal measurement techniques for particle detection, material characterization, and chemical detection are introduced in this paper.

Here, we present three protocols for thermal measurements in microfluidic devices.

在分析微流体装置的热测量技术

Thermal measurement techniques have been used for many applications such as thermal characterization of materials and chemical reaction detection. ...

Development of an Experimental Setup for the Measurement of the Coefficient of Restitution under Vacuum Conditions

The Discrete Element Method is used for the simulation of particulate systems to describe and analyze them, to predict and afterwards optimize their behavior for single stages of a process or even an entire process. For the simulation with occurring particle-particle and particle-wall contacts, the value of the coefficient of restitution is required. It can be determined experimentally. The coefficient of restitution depends on several parameters like the impact velocity. Especially for fine particles the impact velocity depends on the air pressure and under atmospheric pressure high impact velocities cannot be reached. For this, a new experimental setup for free-fall tests under vacuum conditions is developed. The coefficient of restitution is determined with the impact and rebound velocity which are detected by a high-speed camera. To not hinder the view, the vacuum chamber is made of glass. Also a new release mechanism to drop one single particle under vacuum conditions is constructed. Due to that, all properties of the particle can be characterized beforehand.

The coefficient of restitution is a parameter that describes the loss of kinetic energy during collision. Here, a free-fall setup under vacuum conditions is developed to be able to determine the coefficient of restitution parameter for particles in micrometer range with high impact velocities.

实验装置的研制归还系数在真空条件下测量

The Discrete Element Method is used for the simulation of particulate systems to describe and analyze them, to predict and afterwards optimize their ...

How to Build a Vacuum Spring-transport Package for Spinning Rotor Gauges

The spinning rotor gauge (SRG) is a high-vacuum gauge often used as a secondary or transfer standard for vacuum pressures in the range of 1.0 x 10-4 Pa to 1.0 Pa. In this application, the SRGs are frequently transported to laboratories for calibration. Events can occur during transportation that change the rotor surface conditions, thus changing the calibration factor. To assure calibration stability, a spring-transport mechanism is often used to immobilize the rotor and keep it under vacuum during transport. It is also important to transport the spring-transport mechanism using packaging designed to minimize the risk of damage during shipping. In this manuscript, a detailed description is given on how to build a robust spring-transport mechanism and shipping container. Together these form a spring-transport package. The spring-transport package design was tested using drop-tests and the performance was found to be excellent. The present spring-transport mechanism design keeps the rotor immobilized when experiencing shocks of several hundred g (g = 9.8 m/sec2 and is the acceleration due to gravity), while the shipping container assures that the mechanism will not experience shocks greater than about 100 g during common shipping mishaps (as defined by industry standards).

Here we describe how to build a robust spring-transport mechanism for a spinning rotor gauge. This device securely immobilizes the rotor and keeps it under vacuum during transportation. We also describe packaging that minimizes the risk of damage during transport. Tests show our design works for typical shocks during transport.

如何建立一个真空Spring的运输包装为纺转子规

The spinning rotor gauge (SRG) is a high-vacuum gauge often used as a secondary or transfer standard for vacuum pressures in the range of 1.0 x 10-4 Pa to ...

A High Performance Impedance-based Platform for Evaporation Rate Detection

This paper describes the method of a novel impedance-based platform for the detection of the evaporation rate. The model compound hyaluronic acid was employed here for demonstration purposes. Multiple evaporation tests on the model compound as a humectant with various concentrations in solutions were conducted for comparison purposes. A conventional weight loss approach is known as the most straightforward, but time-consuming, measurement technique for evaporation rate detection. Yet, a clear disadvantage is that a large volume of sample is required and multiple sample tests cannot be conducted at the same time. For the first time in literature, an electrical impedance sensing chip is successfully applied to a real-time evaporation investigation in a time sharing, continuous and automatic manner. Moreover, as little as 0.5 ml of test samples is required in this impedance-based apparatus, and a large impedance variation is demonstrated among various dilute solutions. The proposed high-sensitivity and fast-response impedance sensing system is found to outperform a conventional weight loss approach in terms of evaporation rate detection.

This paper presents an impedance-based apparatus for evaporation rate detection of solutions. It offers clear advantages over a conventional weight loss approach: a fast response, high-sensitivity detection, a small sample requirement, multiple sample measurements, and easy disassembly for cleaning and reuse purposes.

蒸发速率检测一种基于阻抗高性能平台

This paper describes the method of a novel impedance-based platform for the detection of the evaporation rate. The model compound hyaluronic acid was ...

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

Flow-assisted dielectrophoresis (DEP) is an efficient self-assembly method for the controllable and reproducible positioning, alignment, and selection of nanowires. DEP is used for nanowire analysis, characterization, and for solution-based fabrication of semiconducting devices. The method works by applying an alternating electric field between metallic electrodes. The nanowire formulation is then dropped onto the electrodes which are on an inclined surface to create a flow of the formulation using gravity. The nanowires then align along the gradient of the electric field and in the direction of the liquid flow. The frequency of the field can be adjusted to select nanowires with superior conductivity and lower trap density. 
In this work, flow-assisted DEP is used to create nanowire field effect transistors. Flow-assisted DEP has several advantages: it allows selection of nanowire electrical properties; control of nanowire length; placement of nanowires in specific areas; control of orientation of nanowires; and control of nanowire density in the device. 
The technique can be expanded to many other applications such as gas sensors and microwave switches. The technique is efficient, quick, reproducible, and it uses a minimal amount of dilute solution making it ideal for the testing of novel nanomaterials. Wafer scale assembly of nanowire devices can also be achieved using this technique, allowing large numbers of samples for testing and large-area electronic applications.

In this paper, flow assisted dielectrophoresis is demonstrated for the self-assembly of nanowire devices. The fabrication of a silicon nanowire field effect transistor is shown as an example.

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 ...