Name: synthesis of hierarchical zno/cdsse heterostructure nanotrees
Uploaded: 2016-11-29T12:30:00.000+00:00
Duration: 6 min 50 s
Description: Watch this Scientific Journal Video about Synthesis of Hierarchical ZnO/CdSSe Heterostructure Nanotrees at JoVE.com

作者感谢Svilen Bobev他与XRD谱图和K Booksh与溅射镀膜机设备援助的帮助。

1.合成树状ZnO /纳米结构CdSSe <ol><li> 蓝宝石衬底的预处理和金涂层 注:金膜作为在ZnO纳米线的生长的催化剂。 <ol><li>清洁蓝宝石幻灯片（a面，10×10×1毫米）在99.5％乙醇，5分钟超声处理以制备金溅射基板上。 </li><li>沉积10纳米（±2纳米）的金厚的薄膜上用溅射镀膜机和黄金目标蓝宝石幻灯片。 </li></ol></li><li>氧化锌纳米线的合成 注:超声处理步骤1.2.2结果在均相ZnO和碳（氧化锌/ C）的混合物。混合后，混合物变为灰色。压实步骤1.2.3确保没有空气存在于混合物和氧化锌和碳紧密接触。 CVD法后，ZnO纳米线的白色膜在基片上进行沉积，朝下朝向船。 <ol><li>混合1克氧化锌纳米粉体和ACTIV的ated碳（50:50质量分数）在10毫升99.5％乙醇并用刮铲搅拌均匀。 </li><li>超声处理水浴中的混合物在20°C 30分钟，然后在80ºC烘干的烘箱中约5小时。 </li><li>放置在ZnO / C的混合物在氧化铝舟用刮刀紧凑很好。 </li><li>放在氧化铝舟的顶部的金涂层蓝宝石载玻片，用金涂覆的一面朝下。放置氧化铝舟中的石英管在水平管式炉的中心。 </li><li>吹扫1小时用Ar的石英管中，在在室温下（RT）40 SCCM的流量。增加从室温至900ºC温度在80ºC/ min的速率，并保持氩气流速率常数。 </li><li>保持在900ºC该温度2小时。通过去除橡胶塞气体入口打开两端的石英管，并让空气进入管，为反应提供氧。 </li><li>保持在900ºC反应温度3小时与るBBER塞子取出。冷却至RT在10℃/分钟的速率。 </li><li>乘船和滑动出炉外。 </li></ol></li><li> CdSSe分行对氧化锌纳米线的沉积 注:硫化镉的氧化铝舟/硒被显示在中心处的石英管中。所制备的氧化锌纳米线被向上并为下游10厘米从船上。该第二CVD法后，为橙色/黄色膜，其是在ZnO / CdSSe纳米结构，应在幻灯片沉积。 <ol><li>混合0.5克硫化镉和硒化镉（硫化镉/硒）粉末以及（50:50质量分数），并放置所述混合物中的氧化铝舟。紧凑型混合好。 </li><li>放置的CdS /硒的氧化铝舟中的石英管中预先制备的氧化锌纳米线样品。 </li><li>吹扫用Ar的管中在室温40SCCm的流速为1小时。提高反应温度到820ºC在80ºC/ min的速率。保持在820ºC该温度下30分钟。 </li><li>冷却到室温以的10℃/分钟的速率。乘船和滑动出炉外。 </li></ol></li><li> ZnO和纳米线CdSSe:对照样品的合成 <ol><li>合成氧化锌纳米线如在相同的实验条件下，第1.2节。 </li><li>合成CdSSe纳米线在第1.3节，在相同的实验条件下，用相同量的硫化镉和硒化镉组成的，但有一个干净的，镀金蓝宝石幻灯片作为基材代替ZnO系沉积滑动。 </li></ol></li></ol> 2.形态和晶体表征<ol><li>安装在SEM阶段的样品与一夹钳，并放置在SEM仪器的真空室中的样品。采取高分辨率模式的SEM图像与在3千伏的电压为12.0毫米的工作距离和3,000倍和1万倍11,12之间的放大率。 </li><li>使用X射线检测器在同一工作距离取EDS数据具有相同的样本12.0毫米。设置仪器来分析模式和调整电压20千伏，导致20至40微安13的电流。 </li><li>收集过滤用Cu靶射线（λ= 1.5418）11,12的X射线粉末衍射仪XRD谱图。 </li></ol> 3，PL发射光谱和时间分辨PL寿命的测量注:PL光谱和时间相关单光子计数（TCSPC）的测量在RT进行了利用放大的钛后二次谐波产生（SHG）蓝宝石振荡器，产生的在400纳米波长为中心50 FSEC脉冲的列车和随着1.76的输出功率14毫瓦。 <ol><li>固定样品进入该位置的样本面到激光器和检测器的试样保持器。对准激光聚焦在样品上。测量样品从500纳米到使用纤维光谱仪900纳米波长下的PL发射光谱。 </li><li>使用单光子探测器（AVA拦车光电二极管或光电管）来测量时间分辨PL寿命有彩色玻璃过滤器和一个500-或650纳米的干扰带通滤波器。 </li><li>插入物的ZnO，CdSSe，或ZnO / CdSSe滑入样品架。测量纯ZnO纳米线与500纳米的带通滤波器和CdSSe或ZnO / CdSSe样品用650纳米的带通滤波器。 </li><li>使用时间相关的单光子计数器或快速示波器测量时间分辨荧光衰减寿命。 </li></ol>

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本文数据和数字是从纳米技术文献Li 等17引用。

ZnO纳米线（茎）的垂直取向是基于在基板上外延生长。 ZnO纳米线沿着与蓝宝石12的一个平面的周期性匹配的&lt;0001&gt;方向优先生长。因此，类型和基片的质量是非常重要的。金涂层的衬底上，从5nm至20nm的厚度不同，已经过测试并表明在ZnO纳米线的生长没有显著差异。的ZnO纳米线的长度可以通过改变在ZnO / C的混合物被使用时，Ar流量率，和空气暴露时间的量来调节。对于具有一致长度合成ZnO纳米线，具有良好定义的比率或人造空气（氧/氮混合物）的氧/氩混合物，建议作为载气。到目前为止，已经在我们的实验室使用这种方法已生长最长ZnO纳米线分别为30微米，并在最短的分别为5微米。 <p class="jove_content"&gt;期间CdSSe沉积，在衬底位置上的温度是控制三元合金组合物中的关键参数。石英管内，从炉朝向端部的中心的温度梯度是由炉设置，管长度和直径，和载气的流率来控制。衬底的位置决定了生长温度，因此，该组合物。因为我们有强烈的迹象表明，CdSSe分支在ZnO茎的生长是外延，如下面所讨论的，发现在用正确的温度为50:50 S的生长在石英管中的位置是很重要的:硒摩尔比（约720℃）14。用于调谐S和Se的摩尔比，多次试验可能是必要的，以找到在管中的正确的设置和位置。所得的ZnO / CdSSe营养素的颜色是是否达到适当的比例的第一指示符;它应该是橙色。明亮的黄色表示高的硫含量，而暗红色表示在CdSSe太多硒。实际比率可以通过EDS或X射线衍射进行测量。 其原因CdSSe分支代替CdSSe /氧化锌核 - 壳结构的形成可通过在晶体结构的测定进行说明。 X射线衍射显示了在26.5°的肩部被识别为CdSSe的闪锌矿相的（111）面（ 图3）16。所述CdSSe枝条的生长可能是由点缺陷的六方晶系的ZnO干的（1010）表面上的启动。闪锌矿相的发生可以通过立方CdSSe的ZnO的（1010）面，通过整数在它们的晶格参数不同，并且能够产生外延生长的生长进行说明。作为枝生长时间越长，晶体结构合并成占在XRD强（101）的信号的更稳定的六方晶相。由于晶格参数是determi由摩尔比定义，和的摩尔比取决于该影响温度是非常关键的所有参数的生长温度，仔细调整。 这是不同的材料在树枝和树干组成树状纳米结构的一个示范。该方法应该在其他材料组合的原则工作。然而，需要以生长枝而非芯 - 壳结构的茎的晶格参数和分支之间的一些关系。此外，该分支材料的沉积温度必须低于该干材料制成，以防止杆的破坏中的最后制备步骤。用于纳米颗粒合成的另一种方法涉及溶剂热增长。已经有大约溶剂热合成方法类似树的复合营养素报告了一把。与溶剂热方法相比，无溶剂CVD是更加环保，使m的准备材料板具有较高的纯度。然而，CVD法也有一些限制。 CVD法通常是在高温度下操作蒸发前体，并制备的样品可具有在升高的温度不同的组合物。 总之，我们制备了一种新的ZnO / CdSSe垂直对准树状纳米结构。无论是氧化锌茎和CdSSe分支机构纤锌矿结构是主要。 TCSPC测量显示从CdSSe分支快速电荷转移到在ZnO茎。所述CdSSe分支的可调谐的BG，在透明的ZnO茎，和两者之间的有效的电荷转移使氧化锌/ CdSSe营养素用于光学，光电和光电应用的有前途的材料。

氧化锌是一种II-VI族半导体，具有3.3电子伏特的带隙（BG），一个高电子迁移率，和一个大的激子结合能1,2。它是具有在光学装置现在和将来的应用，太阳能电池，和光催化登塔丰富半导体材料。然而，氧化锌都是透明的，这限制了它在可见光谱范围内的应用程序。因此，材料吸收可见光，如窄间隙半导体3，染料分子4和光敏聚合物5，经常被用于敏化的ZnO对可见光的吸收。 硫化镉（BG 2.43 EV）和硒化镉（BG 1.76电子伏特）是常见的II-VI族窄禁带半导体，并已深入研究。三元合金CdSSe的BG和晶格参数可以通过改变VI组件6,7的摩尔比进行调整。的ZnO / CdSSe纳米复合材料已被报告导致高效photovoltaic能量转换8,9。 朝着与CdSSe分支的改进的可见光吸收的基板结合垂直取向的ZnO纳米线的有效电子传递途径导致茎和树枝9,10之间有效的电子转移。因此，我们合成了一种新的树状的ZnO / CdSSe纳米结构，其中垂直排列的氧化锌纳米线都装饰有CdSSe分支机构。该复合材料可以作为构建块新颖太阳能转换装置。 这个协议描述如何氧化锌纳米线阵列由由ZnO和C粉末一步法化学气相沉积（CVD）在蓝宝石衬底上生长，之后以前已发表11的过程。以下ZnO纳米线的生长，采用CVD法的第二步骤，以在ZnO纳米线生长CdSSe分支。我们采用X射线粉末衍射（XRD），扫描电子显微镜（SEM），和能量色散X射线谱（EDS）测量晶体结构，形态和在ZnO / CdSSe nanotrees（NTS）的组合物。分支和杆之间的光学性质和电荷载体传输机制已经由光致发光（PL）光谱和时间分辨的PL寿命测量的影响。

<table><tbody><tr><td>ZnO</td><td>Sigma Aldrich</td><td>1314-13-2</td><td></td></tr><tr><td>Activated Carbon</td><td>Alfa</td><td>231-153-3</td><td></td></tr><tr><td>CdSe</td><td>Sigma Aldrich</td><td>1306-24-7</td><td></td></tr><tr><td>CdS</td><td>Sigma Aldrich</td><td>1306-23-6</td><td></td></tr><tr><td>Sapphire</td><td>MTI</td><td>2SP</td><td>a-plane, 10 &amp;times; 10 &amp;times; 1 mm</td></tr><tr><td>Furnace</td><td>Lindberg Blue M</td><td>SSP</td><td></td></tr><tr><td>Scanning electron microscope</td><td>Hitachi</td><td>S5700</td><td>assembled with an Oxford Inca X-act detector</td></tr><tr><td>X-ray powder diffractometer</td><td>Rigaku</td><td>MiniFlex</td><td>filtered Cu K&amp;alpha; radiation (&amp;lambda;=1.5418&amp;nbsp;&amp;Aring;)</td></tr><tr><td>Amplified Ti:sapphire oscillator</td><td>Coherent Mantis</td><td>Coherent Legend-Elite</td><td></td></tr><tr><td>Single photon detection module</td><td>ID Quantique</td><td>ID-100</td><td></td></tr><tr><td>Sputter coater</td><td>Cressington</td><td>308</td><td>assembled with gold target</td></tr><tr><td>Fiber probe spectrometer</td><td>Photon Control</td><td>SPM-002</td><td></td></tr><tr><td>Colored Glass Filter</td><td>Thorlabs</td><td>FGB37-A - &amp;Oslash;25 mm BG40</td><td>AR Coated: 350 - 700&amp;nbsp;nm</td></tr><tr><td>Compressed argon gas</td><td>Keen</td><td>7440-37-1</td><td></td></tr></tbody></table>

synthesis of hierarchical zno/cdsse heterostructure nanotrees

两步化学气相沉积过程是此处使用以制备树状分层的ZnO / CdSSe杂纳米结构。其结构是由CdSSe树枝上生长氧化锌纳米线被一个透明的蓝宝石衬底上垂直排列的。形态是通过扫描电子显微镜测定。晶体结构通过X射线粉末衍射分析来确定。两者的ZnO茎和CdSSe分支具有一个主要为纤维锌矿晶体结构。 S和Se中的CdSSe分支的摩尔比是由能量色散X射线光谱仪进行测定。该CdSSe树枝造成强烈的可见光吸收。光致发光（PL）光谱表明，茎和树枝形成II型异质结。相比于从单个氧化锌茎排放或CdSSe分支时并注明CdSSe和ZnO之间的快速电荷转移PL寿命测量显示，从树上排放的寿命减少。该VERTI卡利对齐的ZnO茎提供一个直接的电子传递途径到基板，并允许由可见光激发后有效的电荷分离。上述特性相结合，使氧化锌/ CdSSe nanotrees有希望的候选人在太阳能电池，光催化，和光电设备的应用程序。

图1显示了氧化锌/ CdSSe营养素的生长机理。该过程涉及催化气 - 液 - 固（VLS）的过程，随后通过非催化汽固体（VS）的增长。在第一VLS步骤，氧化锌和C在Ar气氛中反应，导致金属Zn和碳氧化物。锌随后溶解在蓝宝石基板上的金前体。氧化锌纳米线自溶锌和残留的氧气增长。在第二步骤中，暴露于长ZnO纳米线的通过VLS-VS在短的ZnO种子顶部生长空气的结果。在VLS-VS机制已经详细先前11,12进行了讨论。在最后的步骤中，CdSSe分支直接生长，没有催化剂，在ZnO纳米线。 在第一步骤后获得的ZnO纳米线（协议1.2）的SEM图像示于图2（a）。树状nanostruct的SEM图像（协议1.3）第二步骤之后获得的数目字示于图2（b）和（c）。我们采用EDS来确定营养素的成分。树枝包含S和SE，拥有约0.53摩尔百分比率:0.47。 EDS元素扫描，在与NT三个不同位置进行的，在如图2（c）表示。 图2（D），（e）和（f）示出杆的组合物，分支，和盖，分别。沿图2（G）的行的元素线扫描的映射如图2（H）。元件的扫描显示了端帽和杆可以在示出的杆的区域选自Zn和O的仅贡献扫描清楚区分。通过X射线衍射测定了营养素的晶体结构。他们相比，纯的ZnO和CdSSe纳米线， 图3中所示的晶体结构。纯ZnO和CdSSe纳米线的sh流的预期六方纤锌矿结构，具有的特征峰在（100），（002），（101），和（102）13,15。在（002）氧化锌一个非常强的和窄的峰可以通过垂直排列的ZnO纳米线的一个方向生长进行说明。该营养素的XRD测量结果显示ZnO和CdSSe纤锌矿结构的组合。根据Vegard定律，S的摩尔比:硒从X射线衍射数据确定为0.54:0.46，对应于EDS结果。该CdSSe在营养素表明被分配了闪锌矿相的（111）面和后面讨论的额外的峰。 PL光谱和采用TCSPC时间分辨PL测量分别示于图4（a）和（b）中 ，。在图4（a）中 ，氧化锌，CdSSe和ZnO / CdSSe的荧光发射分别在514纳米，646纳米，627纳米，有最大值。一个500纳米带通滤波器<html>选择用于氧化锌PL寿命测量，而用于测量从CdSSe和ZnO / CdSSe营养素的发射650纳米过滤器。时间分辨PL测量使用单或双指数函数拟合。在图2（b），氧化锌/ CdSSe营养素（0.11纳秒）的PL寿命比任一氧化锌（3.67纳秒）或CdSSe（1.06纳秒）在400纳米激发的寿命短。这可以通过从导带CdSSe的（CB）快速电子转移到ZnO的CB进行说明。在孤立的纳米线，激发电子辐射性重组在纳秒的时间尺度。如果CdSSe分支都与氧化锌的干接触，激发的电子可以从CdSSe传送非辐射的ZnO，以取决于所述接口上，并且可以比辐射寿命快得多时间尺度。因此，氧化锌/ CdSSe营养素的PL寿命被跨越接口的电子转移还原。 "SRC ="/文件/ ftp_upload / 54675 / 54675fig1.jpg"/&gt; 图1. 氧化锌/ CdSSe营养素的合成示意图，炉内的设立显示在左侧。下面的图像示出了三个步骤NT制备涉及:在氩的VLS过程中，空气中的VLS-VS过程，CdSSe分支的沉积。从参考转载。 17. <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54675/54675fig1large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图2" src="/files/ftp_upload/54675/54675fig2.jpg" /> 图2. SEM图像和EDS谱。一 ），通过化学气相沉积制备的ZnO纳米线的SEM图像; b）和c）通过化学气相沉积制备的ZnO / CdSSe营养素的SEM图像;氧化锌干，CdSSe帽，和ZnO / CdSSe营养素的CdSSe分公司的EDS光谱显示在D </强&gt;），e）和f）中 ，分别; H）沿以g所示的线），从参考再现的元素线扫描。 17. <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54675/54675fig2large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图3" src="/files/ftp_upload/54675/54675fig3.jpg" /> 图3 的ZnO，CdSSe，氧化锌/ CdSSe营养素的X射线衍射光谱。（100），（002），（101），和（102）峰，在ZnO和CdSSe纤锌矿结构的裸露纳米线的特性，被示出。从营养素的另外的峰可以在闪锌矿结构CdSSe的（111）面被识别，如文中讨论。从参考转载。 17. <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54675/54675fig3large.jpg" target="_blank">请Ç</a>舔此处查看该图的放大版本。 <img alt="图4" src="/files/ftp_upload/54675/54675fig4.jpg" /> 氧化锌，CdSSe和ZnO / CdSSe营养素兴奋与400纳米波长激光的图4. PL光谱和TSCPC测量。PL光谱（a）和TSCPC测量装有单指数衰减（b）中 。氧化锌，CdSSe和ZnO / CdSSe的PL光谱显示荧光分别为514纳米，646纳米，和627纳米。氧化锌，CdSSe和ZnO / CdSSe的寿命分别为3.67纳秒，1.32纳秒，和0.72纳秒。从参考转载。 17. <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54675/54675fig4large.jpg" target="_blank">请点击此处查看该图的放大版本。</a>

Watch this Scientific Journal Video about Synthesis of Hierarchical ZnO/CdSSe Heterostructure Nanotrees at JoVE.com

Synthesis of Hierarchical ZnO/CdSSe Heterostructure Nanotrees

在这里，我们准备和特点新颖树形层次的ZnO /纳米结构CdSSe，其中CdSSe分支上垂直排列的ZnO纳米线生长。所得nanotrees是用于将太阳能转换和其他光电器件的潜在材料。

分层的ZnO / CdSSe异质Nanotrees的合成

A two-step chemical vapor deposition procedure is here employed to prepare tree-like hierarchical ZnO/CdSSe hetero-nanostructures. The structures are ...

synthesis-of-hierarchical-znocdsse-heterostructure-nanotrees

Nanyang Technological University

Research

JoVE Journal

Chemistry

10.0K 次观看.  University of Delaware. 在这里，我们准备和特点新颖树形层次的ZnO /纳米结构CdSSe，其中CdSSe分支上垂直排列的ZnO纳米线生长。所得nanotrees是用于将太阳能转换和其他光电器件的潜在材料。 

视频: Synthesis of Hierarchical ZnO/CdSSe Heterostructure Nanotrees

Harvesting Solar Energy by Means of Charge-Separating Nanocrystals and Their Solids

Conjoining different semiconductor materials in a single nano-composite provides synthetic means for the development of novel optoelectronic materials offering a superior control over the spatial distribution of charge carriers across material interfaces. As this study demonstrates, a combination of donor-acceptor nanocrystal (NC) domains in a single nanoparticle can lead to the realization of efficient photocatalytic1-5 materials, while a layered assembly of donor- and acceptor-like nanocrystals films gives rise to photovoltaic materials.
Initially the paper focuses on the synthesis of composite inorganic nanocrystals, comprising linearly stacked ZnSe, CdS, and Pt domains, which jointly promote photoinduced charge separation. These structures are used in aqueous solutions for the photocatalysis of water under solar radiation, resulting in the production of H2 gas. To enhance the photoinduced separation of charges, a nanorod morphology with a linear gradient originating from an intrinsic electric field is used5. The inter-domain energetics are then optimized to drive photogenerated electrons toward the Pt catalytic site while expelling the holes to the surface of ZnSe domains for sacrificial regeneration (via methanol). Here we show that the only efficient way to produce hydrogen is to use electron-donating ligands to passivate the surface states by tuning the energy level alignment at the semiconductor-ligand interface. Stable and efficient reduction of water is allowed by these ligands due to the fact that they fill vacancies in the valence band of the semiconductor domain, preventing energetic holes from degrading it. Specifically, we show that the energy of the hole is transferred to the ligand moiety, leaving the semiconductor domain functional. This enables us to return the entire nanocrystal-ligand system to a functional state, when the ligands are degraded, by simply adding fresh ligands to the system4.
To promote a photovoltaic charge separation, we use a composite two-layer solid of PbS and TiO2 films. In this configuration, photoinduced electrons are injected into TiO2 and are subsequently picked up by an FTO electrode, while holes are channeled to a Au electrode via PbS layer6. To develop the latter we introduce a Semiconductor Matrix Encapsulated Nanocrystal Arrays (SMENA) strategy, which allows bonding PbS NCs into the surrounding matrix of CdS semiconductor. As a result, fabricated solids exhibit excellent thermal stability, attributed to the heteroepitaxial structure of nanocrystal-matrix interfaces, and show compelling light-harvesting performance in prototype solar cells7.

A general strategy for the development of charge-separating semiconductor nanocrystal composites deployable for solar energy production is presented. We show that assembly of donor-acceptor nanocrystal domains in a single nanoparticle geometry gives rise to a photocatalytic function, while bulk-heterojunctions of donor-acceptor nanocrystal films can be used for photovoltaic energy conversion.

通过电荷分离纳米晶及其固体收获太阳能

Conjoining different semiconductor materials in a single nano-composite provides synthetic means for the development of novel optoelectronic materials ...

科研

工程学

Seeded Synthesis of CdSe/CdS Rod and Tetrapod Nanocrystals

We demonstrate a method for the synthesis of multicomponent nanostructures consisting of CdS and CdSe with rod and tetrapod morphologies. A seeded synthesis strategy is used in which spherical seeds of CdSe are prepared first using a hot-injection technique. By controlling the crystal structure of the seed to be either wurtzite or zinc-blende, the subsequent hot-injection growth of CdS off of the seed results in either a rod-shaped or tetrapod-shaped nanocrystal, respectively. The phase and morphology of the synthesized nanocrystals are confirmed using X-ray diffraction and transmission electron microscopy, demonstrating that the nanocrystals are phase-pure and have a consistent morphology. The extinction coefficient and quantum yield of the synthesized nanocrystals are calculated using UV-Vis absorption spectroscopy and photoluminescence spectroscopy. The rods and tetrapods exhibit extinction coefficients and quantum yields that are higher than that of the bare seeds. This synthesis demonstrates the precise arrangement of materials that can be achieved at the nanoscale by using a seeded synthetic approach.

A protocol for the seeded synthesis of rod-shaped and tetrapod-shaped multicomponent nanostructures consisting of CdS and CdSe is presented.

硒化镉/硫化镉棒和纳米四脚合成种子

We demonstrate a method for the synthesis of multicomponent nanostructures consisting of CdS and CdSe with rod and tetrapod morphologies. A seeded ...

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, ...

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 ...

Preparation of ZnO Nanorod/Graphene/ZnO Nanorod Epitaxial Double Heterostructure for Piezoelectrical Nanogenerator by Using Preheating Hydrothermal

Well-aligned ZnO nanostructures have been intensively studied over the last decade for remarkable physical properties and enormous applications. Here, we describe a one-step fabrication technique to synthesis freestanding ZnO nanorod/graphene/ZnO nanorod double heterostructure. The preparation of the double heterostructure is performed by using thermal chemical vapor deposition (CVD) and preheating hydrothermal technique. In addition, the morphological properties were characterized by using the scanning electron microscopy (SEM). The utility of freestanding double heterostructure is demonstrated by fabricating the piezoelectric nanogenerator. The electrical output is improved up to 200% compared to that of a single heterostructure owing to the coupling effect of the piezoelectricity between the arrays of ZnO nanorods on the top and bottom of graphene. This unique double heterostructure have a tremendous potential for applications of electrical and optoelectrical devices where the high number density and specific surface area of nanorod are needed, such as pressure sensor, immuno-biosensor and dye-sensitized solar cells.

One-step fabrication method for obtaining freestanding epitaxial double heterostructure is presented. This approach could achieve ZnO coverage with a higher number density than that of the epitaxial single heterostructure, leading to a piezoelectric nanogenerator with an increased output electrical performance.

利用预热水热氧化锌纳米棒/石墨烯/氧化锌纳米棒外延双异质结的机压电纳米发电机的研制

Well-aligned ZnO nanostructures have been intensively studied over the last decade for remarkable physical properties and enormous applications. Here, we ...

Well-aligned Vertically Oriented ZnO Nanorod Arrays and their Application in Inverted Small Molecule Solar Cells

This manuscript describes how to design and fabricate efficient inverted solar cells, which are based on a two-dimensional conjugated small molecule (SMPV1) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM), by utilizing ZnO nanorods (NRs) grown on a high quality Al-doped ZnO (AZO) seed layer. The inverted SMPV1:PC71BM solar cells with ZnO NRs that grew on both a sputtered and sol-gel processed AZO seed layer are fabricated. Compared with the AZO thin film prepared by the sol-gel method, the sputtered AZO thin film exhibits better crystallization and lower surface roughness, according to X-ray diffraction (XRD) and atomic force microscope (AFM) measurements. The orientation of the ZnO NRs grown on a sputtered AZO seed layer shows better vertical alignment, which is beneficial for the deposition of the subsequent active layer, forming better surface morphologies. Generally, the surface morphology of the active layer mainly dominates the fill factor (FF) of the devices. Consequently, the well-aligned ZnO NRs can be used to improve the carrier collection of the active layer and to increase the FF of the solar cells. Moreover, as an anti-reflection structure, it can also be utilized to enhance the light harvesting of the absorption layer, with the power conversion efficiency (PCE) of solar cells reaching 6.01%, higher than the sol-gel based solar cells with an efficiency of 4.74%.

This manuscript describes how to design and fabricate efficient inverted SMPV1:PC71BM solar cells with ZnO nanorods (NRs) grown on a high quality Al-doped ZnO (AZO) seed layer. The well-aligned vertically oriented ZnO NRs exhibit high crystalline properties. The power conversion efficiency of solar cells can reach 6.01%.

定向定向 ZnO 纳米阵列及其在倒小分子太阳电池中的应用

This manuscript describes how to design and fabricate efficient inverted solar cells, which are based on a two-dimensional conjugated small molecule ...

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 ...

Growth of Gold Dendritic Nanoforests on Titanium Nitride-coated Silicon Substrates

In this study, a high-power impulse magnetron sputtering system is used to coat a flat and firm titanium nitride (TiN) film on silicon (Si) wafers, and a fluoride-assisted galvanic replacement reaction (FAGRR) is employed for the rapid and easy deposition of gold dendritic nanoforests (Au DNFs) on the TiN/Si substrates. Scanning electron microscopy (SEM) images and energy-dispersive X-ray spectroscopy patterns of TiN/Si and Au DNFs/TiN/Si samples validate that the synthesis process is accurately controlled. Under the reaction conditions in this study, the thickness of the Au DNFs increases linearly to 5.10 &#177; 0.20 &#181;m within 15 min of the reaction. Therefore, the employed synthesis procedure is a simple and rapid approach for preparing Au DNFs/TiN/Si composites.

This study presents a feasible procedure for synthesizing gold dendritic nanoforests on titanium nitride/silicon substrates. The thickness of gold dendritic nanoforests increases linearly within 15 min of a synthesis reaction.

氮化钛涂层硅基板上金石榴石的生长

In this study, a high-power impulse magnetron sputtering system is used to coat a flat and firm titanium nitride (TiN) film on silicon (Si) wafers, and a ...

Probe Type II Band Alignment in One-Dimensional Van Der Waals Heterostructures Using First-Principles Calculations

Computational tools based on density-functional theory (DFT) enable the exploration of the qualitatively new, experimentally attainable nanoscale compounds for a targeted application. Theoretical simulations provide a profound understanding of the intrinsic electronic properties of functional materials. The goal of this protocol is to search for photocatalyst candidates by computational dissection. Photocatalytic applications require suitable band gaps, appropriate band edge positions relative to the redox potentials. Hybrid functionals can provide accurate values of these properties but are computationally expensive, whereas the results at the Perdew-Burke-Ernzerhof (PBE) functional level could be effective for suggesting strategies for band structure engineering via electric field and tensile strain aiming to enhance the photocatalytic performance. To illustrate this, in the present manuscript, the DFT based simulation tool VASP is used to investigate the band alignment of nanocomposites in combinations of nanotubes and nanoribbons in the ground state. To address the lifetime of photogenerated holes and electrons in the excited state, nonadiabatic dynamics calculations are needed.

Calculations performed by the Vienna Ab initio Simulation Package can be used to identify the intrinsic electronic properties of nanoscale materials and predict the potential water-splitting photocatalysts.