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

University Of Florida, Gainesville FL

Investigators

Abstract

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.