Solid flow drives surface nanopatterning by ion-beam irradiation

Ion Beam Sputtering (IBS) is known to produce surface nanopatterns over macroscopic areas on a wide range of materials. However, in spite of the technological potential of this route to nanostructuring, the physical process by which these surfaces self-organize remains poorly under- stood. We have performed detailed experiments of IBS on Si substrates that validate dynamical and morphological predictions from a hydrodynamic description of the phenomenon. Our results elucidate flow of a nanoscopically thin and highly viscous surface layer, driven by the stress created by the ion-beam, as a description of the system. This type of slow relaxation is akin to flow of macroscopic solids like glaciers or lead pipes, that is driven by defect dynamics.Comment: 12 pages, 4 figure

Reversible Graphene decoupling by NaCl photo-dissociation

We describe the reversible intercalation of Na under graphene on Ir(111) by photo-dissociation of a previously adsorbed NaCl overlayer. After room temperature evaporation, NaCl adsorbs on top of graphene forming a bilayer. With a combination of electron diffraction and photoemission techniques we demonstrate that the NaCl overlayer dissociates upon a short exposure to an X-ray beam. As a result, chlorine desorbs while sodium intercalates under the graphene, inducing an electronic decoupling from the underlying metal. Low energy electron diffraction shows the disappearance of the moir\'e pattern when Na intercalates between graphene and iridium. Analysis of the Na 2p core-level by X-ray photoelectron spectroscopy shows a chemical change from NaCl to metallic buried Na at the graphene/Ir interface. The intercalation-decoupling process leads to a n-doped graphene due to the charge transfer from the Na, as revealed by constant energy angle resolved X-ray photoemission maps. Moreover, the process is reversible by a mild annealing of the samples without damaging the graphene

Monitoring floating microlitter in offshore waters by manta-trawl (collaboration with iFADO project)

Floating marine litter is a recurrent pollutant in the Atlantic and worldwide oceans which has attracted increasing attention in the latest years. Meso- and microplastics derived from industrial pellets or through debris degradation have been also reported in surface and subsurface water samples from Atlantic coast and high-seas. The need of microplastic monitoring and assessment in EU countries and the Atlantic Area calls for the establishment of standardized sampling protocols and methods. In this work, the application of manta-trawl for micro-litter monitoring in coastal and offshore waters of the Galician coast (NW Spain) was assessed. The results obtained in this work suggest a moderate micro-litter density in both coastal and offshore stations. Also, manta-trawl was proved to be a feasible tool for surface and subsurface meso and micro-litter collection

Self-Organized Ordering of Nanostructures Produced by Ion-Beam Sputtering

We study the self-organized ordering of nanostructures produced by ion-beam sputtering (IBS) of targets amorphizing under irradiation. By introducing a model akin to models of pattern formation in aeolian sand dunes, we extend consistently the current continuum theory of erosion by IBS. We obtain new non-linear effects responsible for the in-plane ordering of the structures, whose strength correlates with the degree of ordering found in experiments. Our results highlight the importance of redeposition and surface viscous flow to this nanopattern formation process.Comment: 4 pages, 2 figure

Optimized protocol and template for monitoring floating macrolitter by scientific observers onboard research vessels

In 2007 the Spanish Institute of Oceanography (IEO) established for the first time the group of Apex Predators (marine mammals, seabirds and turtles) observers during a campaign to evaluate pelagic fisheries in the Bay of Biscay (PELACUS 07). This campaign was performed onboard the RV Thalassa, where researchers from the University of La Rochelle carried out the campaign PELGAS, which included apex predator surveys too. Therefore, the same protocol used by French researchers was applied for PELACUS with the aim of facilitating data collection and sharing. This protocol was also adopted by the Spanish research institute AZTI during their campaigns JUVENA and BIOMAN. Since then floating macro litter was incorporated also to the list of observations to be reported by observers to optimize marine debris surveys and allow for an estimation of its density. In the frame of the CleanAtlantic project (Tackling marine litter in the Atlantic Area) the protocol and templates used for recording floating litter were further adapted and improved so that they could be used as a common tool for any observer regardless the specificities of R/V and institutions, and also to facilitate the work of the observers. Thus, the optimized and English-translated protocols and datasheets for apex predators and marine litter recording are presented in the next sections. This work was carried out under the Work Package 5.2, whose final aim is to reinforce and support the monitoring of marine litter in the framework of the Marine Strategy Framework Directive (MSFD)

Breakdown of anomalous channeling with ion energy for accurate strain determination in gan-based heterostructures

The influence of the beam energy on the determination of strain state with ion channeling in GaN-based heterostructures (HSs) is addressed. Experimental results show that anomalous channeling may hinder an accurate analysis due to the steering effects at the HS interface, which are more intense at lower ion energies. The experimental angular scans have been well reproduced by Monte Carlo simulations, correlating the steering effects with the close encounter probability at the interface. Consequently, limitations in the determination of the strain state by ion channeling can be overcome by selecting the adequate beam energy

Coulomb explosion sputtering of selectively oxidized Si

We have studied multiply charged Arq+ ion induced potential sputtering of a unique system comprising of coexisting Silicon and Silicon oxide surfaces. Such surfaces are produced by oblique angle oxygen ion bombardment on Si(100), where ripple structures are formed and one side of each ripple gets more oxidized. It is observed that higher the potential energy of Arq+ ion, higher the sputtering yield of the non conducting (oxide) side of the ripple as compared to the semiconducting side. The results are explained in terms of Coulomb explosion model where potential sputtering depends on the conductivity of the ion impact sites.Comment: 9 pages and 3 figure