Paper PS2-WeA12
MD Simulations of Hydrogen Plasma Interaction with Graphene Surfaces

Wednesday, October 31, 2012, 5:40 pm, Room 25

Due to its unique 2D structure and its outstanding physical, chemical and mechanical properties, graphene is a promising candidate for a large number of novel applications in microelectronics, for transparent conducting electrodes, sensors or energy storage 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 overwhelms current based-plasma technology. Therefore, innovative technological steps have to be developed to allow the growth of graphene layers on large areas wafers and their patterning using conventional lithography and plasma etching schemes.

Due to high ion bombardment energies and significant fragmentation rates, conventional continuous-wave plasma processes are not able to selectively etch ultrathin films without damaging the active layers of nanoelectronic devices. In order to achieve uniform/smooth patterning, doping or chemical modification of graphene films without damaging the substrates, one possible alternative is to use pulsed-plasma discharges which exhibit lower average ion energies (thus minimizing surface damage) and are promising to achieve sub-nm thick layers etching. However, the interactions between reactive pulsed plasmas and surfaces are so complex that the efficient development of new processes requires numerical simulations. Therefore, we propose to develop Molecular Dynamics (MD) simulations to understand the role of ion energy in plasma-graphene interaction and to determine the relationship between the flux/energy of reactive species (ions, radicals) bombarding the surface and its structural/chemical modifications.

In this paper, we investigate the interaction between hydrogen plasma species and single/multilayer graphene 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 ~ 0.7eV to adsorb on the graphene surface. It also appears that the chemical binding of H to sp2-C requires a local rehybridization from sp2 to sp3 resulting in structural changes of the graphene sample. H⁺ bombardment of ABA- and ABC-stacked multilayer graphene sheets are compared and the possibility to store hydrogen between consecutive layers is discussed.