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，但功能越来越强，能够制造出非常微小的金属结构，其物理和化学性质可以为特定应用量身定制，这一点非常重要。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，正在开发利用化学试剂和电子将金属制成纳米级物体的方法。参与该项目的学生在科学会议上展示他们的工作，并在同行评审的期刊上发表论文。他们也有机会在橡树岭国家实验室进行实验，扩大他们的教育经验，同时增加未来职业安置的机会。为了向公众传达科学的兴奋，该项目的参与者正在制作一系列90秒的“微型科技”广播模块和播客，以化学和基于化学的纳米科学的真实应用为特色。聚焦电子束诱导沉积（FEBID）是一种很有前途的纳米制造技术，可以在光子学、催化、传感和等离子体学等领域制造含金属的纳米结构。在这项技术中，电子被用来诱导在真空环境中吸附在固体衬底上的有机金属前体的局部分解。FEBID结合了直写光刻工艺的优点（例如，高空间分辨率，位点特异性，无掩膜，无电阻）和在非平面表面沉积材料的灵活性，允许创建空间和几何上定义良好的三维，含金属的纳米结构。然而，为了使FEBID成为一种广泛应用的纳米制造技术，不仅要控制纳米结构的大小和形状，还要控制纳米结构的化学成分。目前的做法是使用为热过程设计的前驱体，例如化学气相沉积（CVD）。这些CVD前体通常产生FEBID沉积物，具有高水平的有机污染，限制了潜在的应用。该项目旨在解决FEBID材料中的污染问题。本研究对专门为FEBID设计的新型有机金属前驱体进行了合成和评价。这些努力是由表面科学的机械见解指导的。通过开发新的FEBID纳米结构纯化策略，它们也得到了改进。这些结果通过生成电子-分子反应的详细机理信息，提高了对FEBID的理解。反应化学的精心设计可以控制纯度，而电子束聚焦的能力可以控制金属结构的大小和形状，类似于塑料物体的3D打印过程。

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.