The formation of neutral gas phase indium carbide clusters under C60(+) ion bombardment of solid indium was investigated using laser based postionization prior to mass spectrometric detection. Two different postionization methods were used and shown to provide saturated photoionization efficiency, thereby delivering nearly the same information about the composition of the sputtered material. The resulting size distributions of neutral In(m)C(n) clusters are compared with those of the corresponding cationic secondary cluster ions and discussed in terms of calculated cluster properties. Investigating the dependence on C60(+) ion fluence, we demonstrate that clusters containing only one carbon atom are formed in single impact events, whereas the formation of more carbon-rich clusters results from carbon accumulation at the bombarded surface.

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

Context. Top-down chemistry is believed to be responsible for the formation of the large molecular compounds such as the polycyclic aromatic hydrocarbon-like molecules and the fullerenes observed in the interstellar medium. The release of these large molecules from the parent grains remains an important issue to be investigated. Aims. Cosmic rays irradiate the dust grains during their journey in the interstellar medium. In this study we probe to what extent electronic sputtering and/or desorption processes induced by high-energy ion projectiles contribute to the creation of the large molecular component in space. Methods. Carbonaceous dust analogues were produced in an ethylene flame. The resulting soot nanoparticles generated under well-defined conditions were irradiated by swift heavy ions, and mass spectra of the ionic and neutral molecular fragments emitted shortly after the impact were monitored. Results. Large molecular fragments were detected, including neutral and ionic polycyclic aromatic hydrocarbons containing up to several tens of carbon atoms, as well as ionic fullerenes. Although the absolute efficiencies were not obtained, these experiments provide a proof of principle of a top-down scenario involving interaction processes of interstellar dust with high-energy projectiles yielding large molecular compounds observed in space.

Despite the improvement of the quality of CVD grown single-layer graphene on copper substrates, transferring the two-dimensional layer without introducing any unintentional defects still poses a challenge. While many approaches focus on optimizing the transfer itself or on necessary post-transfer cleaning steps, we have focused on developing a pre-treatment of the monolayer graphene on copper to improve the quality and reproducibility of the transfer process. By pressing an ethylene-vinyl acetate copolymer foil onto the monolayer graphene on copper using a commercially available vacuum bag sealer graphene is stabilized by the attachment of functional carbon groups. As a result, we are able to transfer graphene without the need of any supporting layer in an all-H2O wet-chemical transfer step. Despite the general belief that the crumbling of graphene without a support layer in a H2O environment is caused due to differences in surface energy, we will show that this assumption is false and that this behavior is caused rather by the polar interactions between graphene and water. Suppressing these interactions protects graphene from ripping and results in extremely clean, highly crystalline graphene with a coverage close to 100%.

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