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Low temperature plasma-surface interactions : hydrogen plasma and graphene

Lundi 12 novembre 2012 14:00 - Duree : 1 heure 30 minutes
Lieu : Amphithéâtre P015 - Ecole Phelma POLYGONE - 23 rue des partyrs 38000 Grenoble

Orateur : David B. GRAVES ( University of California, Berkeley)
Chaire d'Excellence de la Fondation Nanosciences 2011-2013

Low temperature plasmas are generally far from equilibrium, with different species displaying very different distributions of energy and velocity. This characteristic can be exploited in a vast number of different ways, and this is especially true for applications involving surface modification. The plasma properties can be vastly altered by changing the conditions of the plasma, including the way the elecromagnetic power is delivered to charged species, the gas chemistry, and a multitude of other characteristics. The success of plasma technology in manufacturing semiconductor devices is a leading example.

In this talk, I will begin by discussing some of the reasons that plasma has been so successful in etching nanoscale features. The use of basic studies, both computational and experimental, have been key to these insights. Then, I will address the special case of graphene and the ways that plasma technology may prove to be important in making graphene-based devices. The successful development of graphene-based technologies relies on the capability to grow and integrate this new material into sophisticated devices but the nm-scale control of graphene processing challenges current processing technology, especially conventional lithography and plasma etching. Plasma-graphene interactions must be carefully controlled to avoid damage to the active layers of graphene-based nanoelectronic devices. The use of pulsed-plasmas lowers average ion energies (thus minimizing surface damage) and can be used to control neutral chemistry as well ; however, the use of pulsed plasmas complicates an already complex plasma-surface interaction problem.

We have therefore developed and applied molecular dynamics (MD) simulations, coupled with experiments, to better understand and control the plasma-graphene surface interaction. We investigate the interaction between hydrogen plasma species and single/multilayer graphene nanoribbon (GNR) samples via MD simulations. C-H interatomic potential curves and associated energy barriers are reported depending on the H impact position (top, bridge, hollow or edge sites of GNRs). The influence of graphene temperature and incident species energy on adsorption, reflection and penetration mechanisms is presented. Except for impacts at GNRs edges or at defects location, H species are shown to experience a repulsive force due to delocalized π-electrons which prevents any species with less than 0.6eV to adsorb on the graphene surface. Chemical bonding of H to C requires a local rehybridization from sp2 to sp3 resulting in structural changes of the graphene sample. Energetic H+ bombardment of stacked multilayer graphene sheets are analyzed and the possibility to store hydrogen between adjacent layers is discussed.

*In collaboration with : E. Despiau-Pujo[1], A. Davydova[1], G. Cunge[1], L. Magaud[2] [1] CNRS/UJF-Grenoble/CEA LTM [2] CNRS/UJF-Grenoble/Institut Néel

Contact : stephanie.monfront@fondation-nanosciences.fr

Discipline évènement : (Physique)
Entité organisatrice : (Fondation Nanosciences)
Nature évènement : (Séminaire)
Evènement répétitif : (Graphene in Grenoble) -
Evènement répétitif : (Séminaire mensuel de la Fondation Nanosciences)
Site de l'évènement : Polygone scientifique

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