Detachment Limited Kinetics of Gold Diffusion through Ultrathin Oxide Layers

Gold clusters and nanoparticles on ultrathin oxide layers are used as catalysts and represent essential parts of plasmonic and electronic devices. The stability of these nanostructures at surfaces against the diffusion of their constituents into the bulk is therefore of vital importance regarding their long-term applicability. Here, on the basis of in situ X-ray photoelectron spectroscopy measurements of gold diffusion through ultrathin oxide layers (SiO2 and Al2O3) to a Si substrate, we show that the diffusion from gold clusters/islands into the bulk is a detachment-limited process. Hence, the ultrathin oxide acts principally as a layer preventing a direct contact of metal atoms with the silicon substrate rather than a diffusion barrier. These findings contribute to a quantitative understanding of general design rules of metal/oxide structures.