We show that graphene on a dielectric substrate sustains major modifications if irradiated with swift heavy ions under oblique angles. Due to a combination of defect creation in the graphene layer and hillock creation in the substrate, graphene is split and folded along the ion track yielding double layer nanoribbons. The folded parts are up to several 100 nm in length. Our results indicate that the radiation hardness of graphene devices is questionable but also open up a new way of introducing extended low-dimensional defects in a controlled way.

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The irradiation with fast ions with kinetic energies of > 10 MeV leads to the deposition of a high amount of energy along their trajectory (up to several ten keV/nm). The energy is mainly transferred to the electronic subsystem and induces different secondary processes of excitations which result in significant material modifications. A new setup to study these ion induced effects on surfaces will be described in this paper. The setup combines a variable irradiation chamber with different techniques of surface characterizations like scanning probe microscopy, time-of-flight secondary ion and neutral mass spectrometry, as well as low energy electron diffraction under ultra high vacuum conditions, and is mounted at a beamline of the universal linear accelerator (UNILAC) of the GSI facility in Darmstadt, Germany.Here, samples can be irradiated with high-energy ions with a total kinetic energy up to several GeVs under different angles of incidence. Our setup enables the preparation and in-situ analysis of different types of sample systems ranging from metals to insulators. Time-of-flight secondary ion mass spectrometry enables us to study the chemical composition of the surface, while scanning probe microscopy allows a detailed view into the local electrical and morphological conditions of the sample surface down to atomic scales. With the new setup particle emission during irradiation as well as persistent modifications of the surface after irradiation can thus be studied. We present first data obtained with the new setup, including a novel measuring protocol for time-of-flight mass spectrometry with the GSI UNILAC accelerator.2

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Swift heavy ion induced modifications on graphene were investigated by means of atomic force microscopy and Raman spectroscopy. For the experiment graphene was exfoliated onto different substrates (SrTiO3 (100), TiO2(100), Al2O3(1102) and 90 nm SiO2/Si) by the standard technique. After irradiation with heavy ions of 93 MeV kinetic energy and under glancing angles of incidence, characteristic folding structures are observed. The folding patterns on crystalline substrates are generally larger and are created with a higher efficiency than on the amorphous SiO2. This difference is attributed to the relatively large distance between graphene and SiO2 of d ≈ 1 nm.