Collaborative Research: Surface Reactivity of Organometallic Precursors in Electron- and Ion-Induced Deposition of Metal Nanostructures

佛罗里达大学的Lisa McElwee-White教授和约翰霍普金斯大学的Howard Fairbrother教授得到了化学系大分子、超分子和纳米化学项目的支持，研究了通过化学试剂与聚焦电子和离子束的反应制造金属纳米结构的过程。通过进行拟议的研究获得的洞察力和理解为将金属图案化成各种纳米级物体的方法的发展提供了信息。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。成功实现这个项目的既定目标将导致纳米电子学、催化和传感器发展方面的技术进步。参与这个跨学科研究项目的研究生有机会与行业合作伙伴和国际合作者进行互动，从而增加他们未来就业的机会。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。聚焦带电粒子（电子或离子）束诱导沉积是一种重要的三维金属纳米结构制备技术。纳米制造是通过在低压环境中将有机金属前体分解到基板上实现的。这种纳米制造方法已被用于修复光刻胶、修改集成电路原型以及制造纳米光子、纳米等离子体和纳米磁性器件。控制纳米材料的结构和组成的能力对于它们在纳米器件（如半导体和纳米光电机械系统）中的功能至关重要。除了尺寸和形状控制外，优化这些纳米结构的化学成分也很重要。对于含金属的纳米结构，这通常意味着最大化金属含量。不幸的是，通过带电粒子沉积的纳米结构很少是纯金属的。在聚焦电子束诱导沉积（FEBID）的情况下尤其如此。其原因是商业上可用的有机金属前体是设计用于热沉积过程，如化学气相沉积。本项目通过合成和评价新的定制有机金属前体来解决FEBID前体缺乏的问题，以及FEBID纳米结构材料的纯度和金属含量。这种综合是由表面科学的机械见解指导的。使用低能离子束的研究也已开始。这是由于初步发现表明有机金属配合物与离子的表面反应与电子的表面反应不同。通过开展该项目产生的新知识为新一代性能增强的有机金属配合物的合理合成提供了信息。此外，新开发的前驱体用于研究新型纳米材料的沉积，如氧化物和氮化物。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Professor Lisa McElwee-White of the University of Florida and Professor Howard Fairbrother of Johns Hopkins University are supported by the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry to investigate the process of fabrication of metallic nanostructures through the reactions of chemical reagents with focused electron and ion beams. The insight and understanding gained through conducting the proposed research inform the development of approaches for patterning metals into a variety of nanoscale objects. 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. Success in achieving the stated objectives of this project lead to technological advances in nanoelectronics, catalysis and sensor development. Graduate students involved in this inherently cross-disciplinary research project are afforded opportunities to interact with industry partners and international collaborators, thus enhancing their chances 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 charged particles (electrons or ions) beam induced deposition is an important nanofabrication technique for the creation of three-dimensional metal containing nanostructures. Nanofabrication is enabled by decomposing organometallic precursors onto substrates in a low-pressure environment. This nanofabrication methodology has been used to repair photoresists, modify prototypes of integrated circuits and fabricate nanophotonic, nanoplasmonic and nanomagnetic devices. The ability to control the structure and composition of nanoscale materials is critical for their function in nanodevices, such as semiconductors and nano-opto-electro-mechanical systems. In addition to size and shape control, it is also important to optimize the chemical composition of these nanostructures. For metal-containing nanostructures this typically means maximizing metal content. Unfortunately, nanostructures deposited by means of charged particles are rarely if ever purely metallic. This is particularly true in the case of focused electron beam induced deposition (FEBID). The reason is that the commercially available organometallic precursors are designed for use in thermal deposition processes, such as chemical vapor deposition. This project is addressing the lack of suitable FEBID precursors and the purity and metallic content in FEBID nanostructured materials through synthesis and evaluation of new custom organometallic precursors. The synthesis is guided by mechanistic insights from surface science. Studies using low energy ion beams are also being initiated. This is motivated by preliminary findings that suggest a difference in the surface reactions of organometallic complexes with ions compared to electrons. The new knowledge generated through conducting this project informs the rational synthesis of new generation of organometallic complexes with enhanced performance. In addition, the newly developed precursors are used to investigate the deposition of new classes of nanomaterials, such as oxides and nitrides.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.