Diffusion of Buffer Layer Assisted Grown Gold Nanoclusters on Ru(100) and p(1 × 2)-O/Ru(100) Surfaces

Abstract

Patterning of metallic clusters on surfaces is demonstrated by utilizing a buffer layer assisted laser patterning technique (BLALP). This method has been employed in order to measure the diffusion of AFM and STM characterized size selected gold nanoclusters (5-10 nm diameter), over Ru(100) and p(1 x 2)-O/Ru(100) surfaces. Optical linear diffraction from gold cluster coverage gratings was utilized for the macroscopic diffusion measurements. The clusters were found to diffuse on the surface intact without significant coalescence or sintering. The barrier for metastable gold nanocluster diffusion on the surface is thought to be lower than the energy required for surface wetting. The apparent activation energy for diffusion was found to depend on the cluster size, increasing from 6.2 +/- 0.4 kcal/mol for 5 nm clusters to 10.6 +/- 0.5 kcal/mol for 9 nm clusters. The macroscopic diffusion of gold nanoclusters has been studied on the p(1 x 2)-O/Ru(100) surface as well, where surface diffusion was found to be rather insensitive to the clusters size with activation energy of 5.5 +/- 1 kcal/mol. The difference between the two surfaces is discussed in terms of a better commensurability (higher level of friction) of the gold facets at the contact area with the clean Ru(100) than in the case of the oxidized surface.

Weakly bound buffer layers: A versatile template for metallic nano-clusters growth and film patterning on solid surfaces

“…The great sensitivity of the gold clusters, 3-10 nm in size, to a relatively small difference in the nature of the substrate was explained by the better commensurability of the (1 1 1) oriented gold clusters to the clean Ru(0 0 1). This result in a stronger ''friction" between the gold clusters and the clean ruthenium that increases with the cluster size, therefore stronger dependence on the cluster size was expected and actually reported [23]. Larger mismatch of the structure of Au(111) clusters with the O/Ru(0 0 1) in its (2 Â 2) overlayer structure leads to ''skating" of the clusters as a result of the smaller friction.…”

“…form [23]. This procedure enables one to diffract coherent light (He-Ne laser) from such grating and thus enable direct measurement of clusters diffusion in real time, as a function of clusters size and type of substrate, as schematically demonstrated in Fig.…”

Sublimative desorption of xenon from Ru(100)

“…In addition to its basic importance, the desorption and diffusion kinetics of multilayer Xe on surfaces plays an important role in buffer layer assisted growth [18][19][20][21][22] and laser patterning [23][24][25][26] of metals on surfaces. Used as physisorbed buffer layer between the substrate and metal to be deposited, it induces the formation of abrupt interfaces, resulting in the growth of metallic nanoclusters on any substrate, whose size can be controlled by variation of thickness of the Xe buffer layer.…”

Patterning thin metallic film via laser structured weakly bound template

“…It is therefore possible to utilize laser ablation of weakly adsorbed buffer layers for the removal and patterning of metallic film deposited on top. This overcomes LITD limitations, and has enabled the patterning of metallic films and clusters on surfaces [7][8][9], and the in situ investigation of clusters surface diffusion [10]. Patterning Xe in the form of monolayer grating as a template for hydrogen sticking to silicon was reported earlier by Williams et al [11].…”

“…The details of the experimental setup were described elsewhere [7,8,10]. The method is schematically shown in Fig.…”