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Interaction of highly charged ions with 2D materials
Wilhelm, R. A.ORC
Slow highly charged ions (HCI) provide an efficient toolkit for surface modifications at the nanoscale [1]. Due to the potential energy of HCIs, nanoscale surface melting or atom sputtering can be ob- served in susceptible materials with an efficiency of about 100% (one surface feature per ion). The neutralization of the HCIs driving the potential energy deposition is typically considered to be finished in ’a shallow region’ in the surface, i.e. ’on the first nanometers’. To further quantify the HCI neutral- ization dynamics we recently took a new approach and used freestanding 2D materials as the target. Due to the atomic thickness of the materials, ions are not stopped in the materials and are available for spectroscopic analysis. At the same time the 2D materials are available for post-irradiation microscopic analysis, which finally al- lows us to determine (1) the kinetic and potential energy lost by the ion, (2) the energy dissipated by emission of secondary particles (electrons and photons), and (3) the en- ergy spend in the nanostructure formation process.
By applying our ion beam spectroscopy, we performed charge state and kinetic energy analysis of ions transmit- ted through freestanding single layer graphene (SLG) [2], amorphous 1nm thick Carbon Nanomembranes (CNM) [3], freestanding single layer MoS2, SLG/MoS2 het- erostructures and others. As a first result we found an ultrafast (sub-10 fs ∼ 1 monolayer) neutralization taking place, much faster than established models would have an- ticipated [4]. Furthermore, kinetic energy loss is signifi- cantly enhanced compared to the value of singly charged ions under the same conditions.
To facilitate a comprehensive understanding of the plethora of observed phenomena and their interplay, we use an en- ergy, angle, and charge state resolved spectroscopy in co- incidence with yield and energy resolved measurement of emitted secondary particles [5]. We further developed an exchange and electronic decay taking the time-dependent atomistic model for ion stopping, charge ion charge state explicitly into account [6].
In this contribution I will give an overview about our recent progress in the field of ion scattering from 2D materials and put the results in perspective to nanostructure formation.
  • Invited lecture (Conferences)
    Nanopatterning Workshop, 07.-10.07.2019, Guildford, United Kingdom

Publ.-Id: 29671 - Permalink