title: Epitaxial deposition of silver ultra-fine nano-clusters on defect-free surfaces of HOPG-derived few-layer graphene in a UHV multi-chamber by in situ STM, ex situ XPS, and ab initio calculations.
abstract: The growth of three-dimensional ultra-fine spherical nano-particles of silver on few layers of graphene derived from highly oriented pyrolytic graphite in ultra-high vacuum were characterized using in situ scanning tunneling microscopy (STM) in conjunction with X-ray photoelectron spectroscopy. The energetics of the Ag clusters was determined by DFT simulations. The Ag clusters appeared spherical with size distribution averaging approximately 2 nm in diameter. STM revealed the preferred site for the position of the Ag atom in the C-benzene ring of graphene. Of the three sites, the C-C bridge, the C-hexagon hollow, and the direct top of the C atom, Ag prefers to stay on top of the C atom, contrary to expectation of the hexagon-close packing. Ab initio calculations confirm the lowest potential energy between Ag and the graphene structure to be at the exact site determined from STM imaging.
authors.affiliation: National Centre for Nano-structured Materials, Council for Scientific and Industrial Research (CSIR), Meiring Naude Road, Brummeria, 395 Pretoria, 0001, South Africa. bmwakikunga@csir.co.za.
authors.forename: Gebhu F
authors.initials: GF
authors.lastname: Ndlovu
authors.forename: Wiets D
authors.initials: WD
authors.lastname: Roos
authors.forename: Zhiming M
authors.initials: ZM
authors.lastname: Wang
authors.forename: Joseph Ko
authors.initials: JK
authors.lastname: Asante
authors.forename: Matete G
authors.initials: MG
authors.lastname: Mashapa
authors.forename: Charl J
authors.initials: CJ
authors.lastname: Jafta
authors.forename: Bonex W
authors.initials: BW
authors.lastname: Mwakikunga
authors.forename: Kenneth T
authors.initials: KT
authors.lastname: Hillie