title: Nucleation and growth of cobalt nanostructures on highly oriented pyrolytic graphite.
abstract: Cobalt in the form of three-dimensional (3D) hemispherical clusters (size approximately 10-30 nm) were observed to grow on pristine graphite surfaces via a Volmer-Weber growth mode. X-Ray photoelectron spectroscopy (XPS) reveals that these clusters are physisorbed on the surface. In the presence of minute surface contamination, the morphology of Co changes into a mixture of irregular and hemispherical three-dimensional islands. The formation of irregular islands appears to be mediated by the chemical interactions between Co and the surface contaminants as evidenced from analysis of the carbon pi-pi* transitions. Further analysis of size distribution of Co nanoclusters grown on pristine surfaces shows a critical nucleus size of i* = 1, i.e. a Co dimer forms the smallest stable cluster on a pristine graphite surface.
authors.affiliation: Physics Department, National University of Singapore, 2 Science Drive 3, Singapore, 117542, Singapore.
authors.forename: S W
authors.initials: SW
authors.lastname: Poon
authors.forename: J S
authors.initials: JS
authors.lastname: Pan
authors.forename: E S
authors.initials: ES
authors.lastname: Tok
mesh_terms: D000327:Adsorption; D002244:Carbon / Q000737:chemistry*; D003035:Cobalt / Q000737:chemistry*; D003198:Computer Simulation; D003460:Crystallization / Q000379:methods*; D006108:Graphite / Q000737:chemistry*; D008422:Materials Testing; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D036103:Nanotechnology / Q000379:methods; D010316:Particle Size; D013499:Surface Properties
chemical_list: C009139:pyrolytic carbon; D003035:Cobalt; D002244:Carbon; D006108:Graphite