Experimentally there appears to be a limit to the size of isolated patterns of electrocatalytic nuclei below which electroless metal deposition does not occur. From a model of electroless deposition on small isolated circular spots we conclude that this inhibition effect is caused by an enhanced supply of oxygen to small patterns due to nonlinear diffusion of dissolved oxygen. Since generally the kinetically determined rate of oxygen reduction is larger than that of oxidation of the reducing agent, the open‐circuit potential of nuclei in small patterns cannot be shifted to a sufficiently negative value at which metal deposition is initiated. At relatively large substrates with a high density of small patterns this so‐called oxygen‐diffusion‐size effect may not be noticed since the supply of oxygen is limited by linear diffusion to an effectively planar substrate.

This paper reports on the deposition of Au on cathodically biased p-GaAs electrodes from alkaline KAu(CN)2 solutions in the dark or under illumination. Nucleation and growth of Au have been studied by potentiodynamic and potentiostatic current measurements in combination with scanning and transmission electron microscopy. Au deposition is characterized by progressive nucleation and three-dimensional growth followed by coalescence of Au particles. Different mechanisms of electron transfer processes occurring during nucleation and growth are discussed. Au nucleation in the dark occurs readily at relatively high-doped (>5 • 10LT/cm 3) electrodes, both in the absence and presence of excess CNions. Selective photoinduced nucleation is possible on low-doped (<2 • 10~V/cm3) electrodes in a solution with excess CNions. It is observed that the critical size of Au nuclei is smaller than 1 nm. Growth of previously formed Au nuclei can proceed in the dark and is initially controlled both by kinetic factors and diffusion of Au(CN)2 ions. Our results indicate that only a small potential barrier exists between p-GaAs and deposited Au particles. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 134.117.10.200 Downloaded on 2015-06-22 to IP

Local boiling phenomenaoccurring at a laser irradiated solid-liquid interface were imaged by using high speed photography and video techniques. A stationary gas film was formed at the interface in a broad range of laser powers. Bubble formation occurred at higher laser powers and was greatly facilitated by deposited particles on the substrate. Electron microscopy investigations showed the typical occurrence of craters in laser-induced metal spots produced at relatively high laser intensities. These craters are due to the removal or migration of previously deposited metal particles from the center of the laser spot. Also the presence of a gas film or a bubble at the laser spot center or convective currents in the liquid may cause cratering. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 169.230.243.252 Downloaded on 2015-03-11 to IP Vol. 134, No. I1 L A S E R -I R R A D I A T E D 11 ----7 ~l 3A/ 16 I-:" V / 2 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 169.230.243.252