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Surface reaction/nanostructuring

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Involved people : Aditya Agnihotri, Philippe Boduch, Brigitte Ban d’Etat, Abdenacer Benyagoub, Amine Cassimi (AMA), Alicia Domaracka (AMA), Clara Grygiel, Isabelle Monnet, Henning Lebius, Jean-Marc RamilIon (Mechanical workshop, design office),Frédéric Ropars (Electronics), Hermann Rothard

Contracts : ANR international SIISU (2013-2016), PELIICAEN (2013-2015), CAPES-COFECUB, Fusion, crédits d’intervention CNRS

Surface structures induced by swift ion impact in grazing incidence. From left to right : series of hillochs on SrTiO3, cut and fold of graphene/SiO2 et long troughs on SiC.
O. Ochedowski, O. Osmani, M. Schade, B. Kleine Bussmann, B. Ban-d’Etat, H. Lebius and M. Schleberger, Nature Communications 5, 3913 (2014)

Surface nanostructuration

Irradiations with swift heavy ions under grazing incidence allow the modification of surfaces in unique ways. The energy loss necessary to achieve these modifications (evidence by AFM) is much lower than for normal incidence irradiation. Several modification types were observed, like lines of hillocks and troughs. One structure is obtained per incident ion, allowing large-scale surface modifications at low ion fluences.

Irradiation under grazing angle is a unique way to cut and fold graphene. At small incidence angles, the graphene opens like a window. At larger incidence angles, several pieces are cut out of the graphene layer and then folded.

Surface reaction

Since 2008, in close collaboration within a French-Brazilian exchange program CAPES-COFECUB, we started studying irradiation effects in astrophysical materials and in LiF. The ultrahigh vacuum XY-TOF-SIMS (imaging time of flight- secondary ion mass spectrometry) system AODO was used from 2008 to 2011 at GANIL-SME (electronic sputtering regime MeV/u) and we obtained e.g. results on Li+(LiF)n cluster emission and the evolution of angular distributions and energy distributions with cluster size. Also, cluster ion ejection as a function of the electronic energy loss and the thickness of in situ prepared thin LiF films was studied. An important result is the observation of thresholds for the formation of large clusters, which are only emitted for sufficiently thick films and beyond a certain amount of deposited energy. Thin films of CaF2 on Si, and CaF2 crystals were also investigated. Furthermore, the silicate nepheline, a model for surfaces of solar system bodies (Mercury, Moons) was studied, since sputtered particles contribute to the formation of their exospheres. The TOF-SIMS analysis allows also to study the evolution of surface stoichiometry under impact of charged particles. Since 2012, AODO was mounted at ARIBE and the analysis of LiF and nepheline extended to slow highly charged ions. Since 2014, AODO is upgraded with a cold head allowing to study materials, including ices of astrophysical interest, at low temperature. As in the case of LiF, with water ice, most of the emitted secondary ions are protonated water clusters H+(H20)n.