Diffusion controlled growth of metallic nanoclusters at selected surface sites

Abstract

We have investigated the growth of three-dimensional Ag particles at atomic steps on the surface of highly oriented pyrolytic graphite using a scanning electron microscope. By controlling the growth parameters the cluster growth was confined to the steps avoiding terrace nucleation. In this way quasi-one-dimensional chains of Ag nanoclusters of approximately 10 nm diam were produced. The results suggest the viability of an important new route to the creation of controlled nanoscale structures. A comprehensive surface study indicates that cluster mobility and coalescence play an important role in the growth mechanism on the steps. Evidence was also found that the graphite surface has several different types of surface steps. A quantitative analysis of the cluster distribution on the steps was performed, to investigate the nucleation and growth processes at temperatures from 50 to 205 °C.

Energetic Impact of Size-Selected Metal Cluster Ions on Graphite

“…From the lower coordination number of the carbon atoms at the step it is expected that the steps have a higher chemical activity than the basal plane, leading to preferential nucleation of mobile species along the steps and a zone of depleted island density about the step. This behavior has been noted for both Ag atoms and Ag 400 clusters on graphite [16,17]. Figure 2(b) shows the behavior near a step for the deposition of Ag 3 2 cluster ions at 150 eV [cf.…”

“…While graphite is a natural (and popular) substrate for cluster deposition and diffusion experiments [5,[15][16][17], the impact of metal clusters on graphite has not previously been modeled. However, recent experiments [18,19] and simulations [19][20][21][22][23][24] concerned with the impact of energetic (atomic and cluster) ions on this surface provide an invaluable reference point for interpreting the novel features of the cluster-surface interaction.…”

Magnetic properties of cobalt and cobalt–platinum nanocrystals investigated by magneto-optical Kerr effect

“…Due to this increased surface mobility, the nanocrystals move to decorate lines forming along the atomic steps of the substrate. 52 Due to the tip convolution it is not possible to distinguish if the nanocrystals are coalesced or not. But up to 800 K, the height of the CoPt monolayer is constant, equal to 7Ϯ2 nm, which is consistent with the TEM results.…”

Controlled growth of uniform silver clusters on HOPG

“…When irradiated with fluorescent light, spherical Ag particles can reform into triangular nano-prisms, which could be used for multicolor diagnostic labeling [2]. In terms of its easy preparation, stable and well-defined structure, as well as its weak interactions with metals, highly oriented pyrolytic graphite (HOPG) surface has been extensively used as substrate for growth of Ag clusters (particles) from different forms of Ag [3][4][5][6][7][8], as driven by their great application potential in industrial chemical catalysis.…”

“…In most vapor deposition methods, Ag growth on HOPG usually proceeds via the three-dimensional Volmer-Weber mode, as established by STM [3,5,6,10] and SEM [4] observations, and by molecular dynamics simulations [9]. Small clusters are nucleated randomly on the substrate and then coalesced into large islands, due to high mobility of Ag atoms and stronger interaction among them (compared to the Ag-substrate interaction terraces are wide enough, cluster grouping could happen which creates small irregularly shaped groups of clusters.…”