Graphene to Graphane Transition Induced by Highly Charged Ion Irradiation

(1) AG Schleberger, Universität Duisburg-Essen, Lotharstraße 1, 47048-Duisburg, Germany
(2) AG Hasselbrink, Universität Duisburg-Essen, Universitätsstraße 5, 45141-Essen, Germany

Since its isolation in 2004 by Geim and Novoselov, graphene has attraced a lot of attention from researchers of various fields. Although its intrinsic physical properties are extraordinary when it comes to charge carrier mobility, thermal conductivity, mechanical strength, etc., some applications will require modifications of pristine graphene. One possibility consists of introducing defects into the graphene lattice to e.g. create nanopores in graphene for ultrafiltration filters. Furthermore, the presence of defects affects the adsorbtion of adsorbates on graphene and can be used to create graphene derivatives like fluorographene, graphene oxide or hydrogenated graphene (al so called graphane).   In this contribution it will be shown, that highly charged ions (HCI, ions with a relatively low kinetic energy and a high potential energy due to their charge state) provide a powerful tool to introduce defects into a graphene sheet [1,2]. These projectiles are interacting with matter primarily via electronic excitation exclusively in the first few nanometers at the surface. Using atomic force microscopy and Raman spectroscopy, defects due to the HCI irradiation can be observed in graphene. Interestingly, the defects are not of topographic nature but can only be observed in the friction image. Additional sum frequency generation measurements indicate that upon ion impact, graphene is locally hydrogenated. Finally in situ transport measurements of an irradiated graphene field effect device are presented which allows us to correlate the effect of the local hydrogenation with the charge carrier mobility and doping of the modified graphene device.  

[1] Hopster et al. 2D Materials 1:011011 (2014)
[2] Wilhelm et al. Phys. Rev. Lett. 112:153201 (2014)