Physikalisches Kolloquium: Prof. Dr. Friedrich Aumayr (TU Wien)

Probing 2D-materials by slow highly charged ions

19.02.2019 ab 16:15

Leibnizstr. 13, 24118 Kiel, Hans-Geiger Hörsaal

Abstract

Highly charged ions - along with femto- and attosecond light sources - provide a unique tool for
probing the electronic response of solid materials to an extremely strong electric field, the
Coulomb field of an approaching highly charged ion [1, 2]. In our experiments we study the ultra-
short time response of different 2D-materials like graphene and MoS 2 to an incoming highly
charged ion (typically Xe 40+ ). In a multi-coincidence setup [3] we measure the charge state and
energy of highly charged ions transmitted through suspended 2D-membranes in coincidence
with the number of emitted electrons. This allows us to derive the relevant time scales for charge
transfer along the 2D-layer, the resulting current densities in the material and lower bounds for
the breakdown currents. Depending on electron mobility some 2D materials fail to resupply the
lost charges and/or fail to dissipate the absorbed energy on a timescale small compared to lattice
vibrations. The resulting Coulomb explosion tears holes of the order of some nanometers into the
2D membrane [4], which are observed in high resolution (S)TEM investigations. The results of our
studies are therefore of interest for engineering two-dimensional materials with electrons, ions,
and lasers, with many prospective applications like their use as molecular sieves, for desalination
or even DNA sequencing.

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