Low energy ion irradiation of 2D-materials

• Applicant: Professor Dr. Thomas Werner Michely
• Subject Area: Experimental Condensed Matter Physics ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: from 2015 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 282318026

The objective of the research within this follow-up proposal is to discover and investigate ion irradiation induced phenomena in supported 2D-materials. On the one hand, we will complete research that started already in the first project phase by investigating topics from new viewpoints that developed meanwhile, by supplementing existing data sets, as well as through publication of results in order to advance and stimulate further research. On the other hand, we will build on significant findings and achievements that emerged during the first funding period to explore scientific new ground.I. Nanomesh: Driven by the rising interest in application of 2D-materials as membranes, we will exploit the unique moiré-based ion beam approach for the realization of such membranes. We will refine and develop our work on the vacancy cluster nanomeshes in graphene and hexagonal boron nitride supported by Ir(111) or Pt(111). On the fundamental side we will conduct additional experiments, calculations and modelling to understand the formation of the magic vacancy cluster sizes discovered and the mechanism giving rise to a bimodal vacancy cluster size distribution. On the practical side, we intend to optimize the recipes for nanomesh formation in terms of regularity, uniform and tunable size, as well as the absence of larger vacancy islands that would deteriorate an application as filtering membrane. Moreover, we will establish the transfer of these nanomesh layers and characterize them by transmission electron microscopy. II. Phase transitions in transition metal disulfides: With the availability of transition metal disulfide monolayers as quasi-freestanding layers on graphene on Ir(111) it becomes possible to investigate how ion beams can induce phase transitions in these materials. As a paradigm, we will fully characterize the reversible ion beam induced crystalline-to-amorphous transition of MoS2 including scanning tunneling spectroscopy and microscopy, photoluminescence, as well as Raman spectroscopy. We will furthermore investigate how ion beams can be used to induce other structural phase transitions in such layers. III. High pressure chemistry and isotope separation: Finally, we will utilize our finding that implanted gases are trapped in blisters underneath graphene or hexagonal boron nitride monolayers on Ir(111) at GPa pressures, even when these layers are highly defective. This finding implies a potential for high pressure chemistry, if blisters can be filled with reactive gases. Moreover, as we found that the temperature dependent gas retention also depends on the gas species, we will explore whether this effect may also be used for isotope separation, e.g. for the separation of hydrogen and deuterium.

• DFG Programme: Research Grants