Adhesion, mobility and aggregation of nanoclusters at surfaces: Ni and Ag on Si, HOPG and graphene

Abstract

An experimental investigation of Ag and Ni nanoparticles (NPs) deposited on Silicon with its native oxide, on highly oriented pyrolytic graphite and on graphene flakes is reported. The NPs were physically synthesized with a magnetron based gas aggregation source and the produced beam was mass-filtered and deposited in vacuum on the substrates. The study was concentrated on the morphology for the different cases, shedding some light on the interaction of pre-formed NPs with surfaces, a crucial aspect both of technological and scientific relevance. The nature of adhesion can be strongly influenced by the intrinsic properties of the surface (like for instance the energetics of interaction between the NP surface atoms and the first layers of the substrate) and/or the extrinsic properties, like the presence of defects, step edges, impurities and other irregularities. After adhesion, the NPs mobility and their mutual interaction are very relevant. In this work, the study was concentrated on NP/surface morphology, by using atomic force microscopy, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. Article highlights Morphology of physically synthesized metal Nano-Particles (NPs) on Si, HOPG and Graphene was investigated. The NPs were pure Ag and Ni. Coalescence, diffusion and self-aggregation and preferential adhesion were observed, with possible applications in sensor technology. Possible explanations are: NP softness, NP/surface bonding interaction and presence of contaminant species molecules between NP.

Morphology and Optical Properties of Gas-Phase-Synthesized Plasmonic Nanoparticles: Cu and Cu/MgO

“…For N aggr ≈ 3%, d = 11.4 nm, and F = 0.1 NP/s cm 2 , a value D ≈ 8•10 −11 cm 2 s −1 was obtained. This quantity is of the same order of magnitude as the one obtained for Ni NPs [41] but smaller (by a factor of 12) than in the case of Sb NPs with d = 6 nm on carbon films, found by Bardotti et al [40], where D ≈ 10 −9 cm 2 /s at room temperature. The reason for this discrepancy can be the use of different substrates for the two experiments, a higher degree of adhesion of Cu NPs to the surface than Sb, and the much larger size of Cu NPs in the present experiment.…”

“…The diffusion and agglomeration of NPs on carbonaceous supports (especially HOPG) were previously studied [40,41]. This phenomenon was also investigated in the present study.…”