Collaborative Research: Designing Organometallic Precursors for Focused Electron Beam Induced Deposition of Metal Nanostructures

随着智能手机等电子设备变得越来越小，但功能越来越多，能够创建非常微小的金属结构非常重要，这些金属结构的物理和化学特性可以为特定应用量身定做。这不仅需要控制结构、大小和形状，还需要控制化学成分。在这个项目中，正在开发使用化学试剂和电子将金属图案化成纳米级物体的方法。参与这个项目的学生在科学会议上展示他们的工作，并在同行评议的期刊上发表论文。他们还有机会在橡树岭国家实验室进行实验，拓宽了他们的教育经验，同时增加了未来职业安置的机会。为了向公众传播科学的兴奋，该项目的参与者正在制作一系列90秒的“微小科技”无线电模块和播客，以化学和基于化学的纳米科学在现实世界中的应用为特色。聚焦电子束诱导沉积(FEBID)是一种很有前途的纳米加工技术，它可以制造出用于光子学、催化、传感和等离子体等领域的含金属纳米结构。在这项技术中，电子被用来诱导吸附在固体衬底上的有机金属前体在真空环境中的局部分解。FEBID将直写光刻工艺的优点(例如，高空间分辨率、位置专一性、无掩膜、无抗蚀剂)与在非平面表面沉积材料的灵活性结合在一起，从而能够创建空间和几何上定义良好的三维含金属纳米结构。然而，为了使FEBID成为一种广泛适用的纳米制造技术，不仅必须对纳米结构的大小和形状进行控制，还必须对纳米结构的化学成分进行控制。目前的做法是使用为化学气相沉积(CVD)等热过程设计的前体。这些CVD前体通常会产生有机污染水平较高的FEBID沉积物，限制了潜在的应用。该项目正在解决FEBID材料中的污染问题。这项研究合成并评价了专门为FEBID设计的新的有机金属前驱体。这些努力是由表面科学的机械论见解指导的。通过开发新的FEBID纳米结构纯化策略，它们也得到了改进。这些结果通过产生关于电子-分子反应的详细机制信息，提高了对FEBID的理解。精心设计的反应化学可以控制纯度，而聚焦电子束的能力可以控制金属结构的大小和形状，这类似于塑料物体的3D打印。

As electronic devices such as smartphones become smaller but have more capability, it is important to be able to create very tiny metal structures whose physical and chemical properties can be tailored for specific applications. This requires control over not only structure, size and shape but also chemical composition. In this project, methods are being developed for patterning metals into nanoscale objects by using chemical reagents and electrons. Students involved in this project present their work at scientific meetings and publish papers in peer reviewed journals. They also have the opportunity to conduct experiments at Oak Ridge National Laboratory, broadening their educational experience while enhancing opportunities for future career placement. To communicate the excitement of science to the general public, participants in the project are generating a series of 90-second "Tiny Tech" radio modules and podcasts that feature real world applications of chemistry and chemistry-based nanoscience. Focused electron beam induced deposition (FEBID) is a promising nanofabrication technique that can create metal-containing nanostructures for photonics, catalysis, sensing and plasmonics. In this technique, electrons are used to induce local decomposition of organometallic precursors adsorbed onto solid substrates in a vacuum environment. FEBID combines the advantages of direct-write lithographic processes (e.g., high spatial resolution, site-specificity, mask-less, resist-less) with the flexibility to deposit materials on non-planar surfaces, allowing creation of spatially and geometrically well-defined three-dimensional, metal-containing nanostructures. For FEBID to emerge as a broadly applicable nanofabrication technique, however, control must be exerted over not just the size and shape, but also the chemical composition of the nanostructures. The current practice is to use precursors designed for thermal processes, such as chemical vapor deposition (CVD). These CVD precursors generally create FEBID deposits with high levels of organic contamination, limiting potential applications. This project is addressing the issue of contamination in FEBID materials. This research synthesizes and evaluates new organometallic precursors designed specifically for FEBID. The efforts are guided by mechanistic insights from surface science. They are also improved by developing new purification strategies for FEBID nanostructures. The results are improving the understanding of FEBID by generating detailed mechanistic information on the electron-molecule reactions. Careful design of the reaction chemistry allows control of the purity while the ability to focus electron beams allows control of the size and shape of the metal structure in a process analogous to 3D printing of plastic objects.