Interaction Between Energetic Ions and Freestanding 2D Materials

Ivan Shorubalko
August 8th, 2018 IVAN SHORUBALKO Empa, Dübendorf

A large part of graphene and related 2D materials research is devoted to its nanostructuring or modification on atomistic scale. The field is driven by numerous novel properties and practical applications. Sputtering by energetic focused ion beams (FIBs) has been envisioned and to a large extend demonstrated as a powerful method to create nanostructures in graphene. Here we summarize our activities of the last few years on pushing the limits of this technique in several aspects: resolution, reproducibility, homogeneity, and throughput. Sputtering yields of free-standing graphene by He- and Ga- FIBs are experimentally determined. Defect density is measured by irradiation dose and compared to the extracted from Raman D to G peaks ratio. Few-nm-small pores in graphene are demonstrated by He- and Ga-FIBs sputtering. We show that essential understanding of the graphene (or any other 2D material) sputtering by FIBs can be done by rather simple binary collision theory. The main pecu liarity of the FIBs interaction with 2D membranes is absence of collision cascades, eventually no interaction volume. Thus, the patterning resolution is directly set by the beam diameters. Pore diameter as function of exposure dose reveals the ion-beams profiles. Compared to transmission electron microscope (TEM) the high throughput of nano-pore formation in 2D membranes by FIBs makes the method as precise but much more practical for fabrication of large amount of pores. A million of few-nm-small pores with narrow size distribution were fabricated in free-standing graphene. Such perforated ultrathin membranes find their applications in the field of quick and energy efficient filtration.

Seminar, August 8, 2018, 14:00. Seminar Room

Hosted by Prof Frank Koppens