Graphene-and-Metal-Based Atomically Precise Nanoelectronics

Project Summary The goal of the project is to develop fabrication methods for graphene- and metal-based nanostructures with atomically precise edges and boundaries, and to perform comprehensive variable-temperature magnetotransport measurements on these samples for comparison with theoretical predictions. Other goals include the scientific exploration of graphene- and metal-based devices with all three spatial dimensions smaller than 10 nm, and phenomena derived from this quantum confinement, including the opening of an orientation- and width-dependent energy gap, unusual quantum confinement effects due to the massless graphene charge carriers, and half-metallic behavior of graphene of interest for spintronic applications. The long-term objectives of the project are 1) precise control over the fabrication of such samples so that the deleterious effects of edge defects (vacancies) and the like can be avoided, and 2) a detailed understanding of their physics so that the fUll power of their electronic properties can be harnessed. A second theme of the project is the use of mass transport processes due to applied currents, magnetic fields, temperature gradients, and vapor flow to achieve atomically precise nanofabrication. This detailed investigation of atomic- scale mass migration effects will have broad impact on the understanding of aging and failure of nanoscale devices, as the two are closely linked. Methods of atomically precise nanofabrication will be based on Feedback Controlled Electromigration of metal constrictions. This method will enable creation of metal etch with masks atomically smooth edges that will be used to define graphene nanostrips with all three dimensions smaller than 10 inn in size. Metal nanoparticles will be used to catalytically etch graphene along into nanoribbons whose edges run parallel to well defined crystal axes of the carbon lattice. (Iraphene point contacts will be formed by direct FCE. Metal nanowires with integrated contacts and atomically precise sidewalls will be fabricated by controlling the thermal gradients that develop during FCE. Micrometer-long nanowires with atomically smooth sidewalls will be produced by performing the FCE process with simultaneous independent control of thermal gradients provided by integrated heaters. Details of the thermal gradients and their evolution will be directly measured with nanoscale spatial resolution and 100 jis - 1 ms time resolution. The intellectual merit of program lies in its innovative approach to create fabrication methods combining the desirable characteristics of "top down" and "bottom up" methodologies, as well as its exploration of the frontiers of graphene- and metal-based nanoelectronic devices. The broader impact of the work lies in education and outreach, international collaboration, and impact on other fields in science and engineering. Training will be provided to graduate students, undergraduates, and high school students in a dynamic and interdisciplinary research environment. Outreach and education efforts by the PIs will include a partnership with the Penn Science Teachers Institute to provide research experiences for their teacher graduates and to develop short courses to increase the content knowledge of high school science teachers. Philadelphia's K- 12 community will be engaged through participation in the annual "NanoDay~PENN", including technical posters from the group and presentations appropriate for a general audience. Research infrastructure will be enhanced through an international partnership with NanoAFNET, the Nanosciences African Network; the group will host up to three scientists per year with research interests in the area of nanoelectronics and nanomaterials.