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

佛罗里达大学的丽莎·麦克尔维-怀特教授和约翰·霍普金斯大学的霍华德·费尔布罗泽教授得到化学系大分子、超分子和纳米化学项目的支持，研究通过化学试剂与聚焦电子束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所获得的洞察力和理解为将金属图案化为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，重要的是能够创建非常微小的金属结构，其物理和化学特性可以针对特定应用进行定制。这不仅需要控制结构、尺寸和形状，还需要控制化学成分。 成功实现该项目的既定目标将导致纳米电子学、催化和传感器开发方面的技术进步。 参与这个固有的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互动，从而提高他们未来职业生涯的机会。 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“微小技术”无线电模块和播客，其中包括化学和基于化学的纳米科学的真实的世界应用。聚焦带电粒子（电子或离子）束诱导沉积是一种重要的纳米纤维技术，用于创建三维含金属纳米结构。 通过在低压环境中将有机金属前体分解到衬底上来实现纳米纤维。 这种纳米制造方法已被用于修复光致抗蚀剂，修改集成电路的原型和制造纳米光子，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（例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，优化这些纳米结构的化学组成也很重要。 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。 原因在于市售有机金属前体被设计用于热沉积工艺，例如化学气相沉积。 该项目通过合成和评估新的定制有机金属前体来解决缺乏合适的FEBID前体以及FEBID纳米结构材料中的纯度和金属含量的问题。 合成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正在开始。 这是出于初步的发现，表明与电子相比，金属有机配合物与离子的表面反应的差异。 通过开展该项目产生的新知识为新一代有机金属配合物的合理合成提供了信息，并提高了性能。 此外，新开发的前体被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NSF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.