title: Single impacts of keV fullerene ions on free standing graphene: Emission of ions and electrons from confined volume.
abstract: We present the first data from individual C60 impacting one to four layer graphene at 25 and 50 keV. Negative secondary ions and electrons emitted in transmission were recorded separately from each impact. The yields for C(n)(-) clusters are above 10% for n ≤ 4, they oscillate with electron affinities and decrease exponentially with n. The result can be explained with the aid of MD simulation as a post-collision process where sufficient vibrational energy is accumulated around the rim of the impact hole for sputtering of carbon clusters. The ionization probability can be estimated by comparing experimental yields of C(n)(-) with those of C(n)(0) from MD simulation, where it increases exponentially with n. The ionization probability can be approximated with ejecta from a thermally excited (3700 K) rim damped by cluster fragmentation and electron detachment. The experimental electron probability distributions are Poisson-like. On average, three electrons of thermal energies are emitted per impact. The thermal excitation model invoked for C(n)(-) emission can also explain the emission of electrons. The interaction of C60 with graphene is fundamentally different from impacts on 3D targets. A key characteristic is the high degree of ionization of the ejecta.
authors.affiliation: Department of Chemistry, Texas A&M University, College Station, Texas 77843-3144, USA.
authors.forename: Stanislav V
authors.initials: SV
authors.lastname: Verkhoturov
authors.affiliation: Department of Chemistry, Texas A&M University, College Station, Texas 77843-3144, USA.
authors.forename: Sheng
authors.initials: S
authors.lastname: Geng
authors.affiliation: Institute of Condensed Matter and Nanosciences-Bio and Soft Matter (IMCN/BSMA), Université Catholique de Louvain, 1 Croix du Sud, B-1348 Louvain-la-Neuve, Belgium.
authors.forename: Bartlomiej
authors.initials: B
authors.lastname: Czerwinski
authors.affiliation: Materials Characterization Facility, Texas A&M University, College Station, Texas 77843-3122, USA.
authors.forename: Amanda E
authors.initials: AE
authors.lastname: Young
authors.affiliation: Institute of Condensed Matter and Nanosciences-Bio and Soft Matter (IMCN/BSMA), Université Catholique de Louvain, 1 Croix du Sud, B-1348 Louvain-la-Neuve, Belgium.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Delcorte
authors.affiliation: Department of Chemistry, Texas A&M University, College Station, Texas 77843-3144, USA.
authors.forename: Emile A
authors.initials: EA
authors.lastname: Schweikert