Morphology Evolution of Nanoscale-Thick Au/Pd Bimetallic Films on Silicon Carbide Substrate

Bimetallic Au/Pd nanoscale-thick films were sputter-deposited at room temperature on a silicon carbide (SiC) surface, and the surface-morphology evolution of the films versus thickness was studied with scanning electron microscopy. This study allowed to elucidate the Au/Pd growth mechanism by identifying characteristic growth regimes, and to quantify the characteristic parameters of the growth process. In particular, we observed that the Au/Pd film initially grew as three-dimensional clusters; then, increasing Au/Pd film thickness, film morphology evolved from isolated clusters to partially coalesced wormlike structures, followed by percolation morphology, and, finally, into a continuous rough film. The application of the interrupted coalescence model allowed us to evaluate a critical mean cluster diameter for partial coalescence, and the application of Vincent’s model allowed us to quantify the critical Au/Pd coverage for percolation transition

Characteristics of Pd and Pt Nanoparticles Produced by Nanosecond Laser Irradiations of Thin Films Deposited on Topographically-Structured Transparent Conductive Oxides

Pd and Pt nanoparticles on Fluorine-doped tin oxide (FTO) are produced. This outcome is reached by processing nanoscale-thick Pd and Pt films deposited on the FTO surface by nanosecond laser pulse. Such laser processes are demonstrated to initiate a dewetting phenomenon in the deposited metal films and lead to the formation of the nanoparticles. In particular, the effect of the film’s thickness on the mean size of the nanoparticles, when fixed the laser fluence, is studied. Our results indicate that the substrate topography influences the dewetting process of the metal films and, as a consequence, impacts on the nanoparticle characteristics. The results concerning the Pd and Pt nanoparticles’ sizes versus starting films thickness and substrate topography are discussed. In particular, the presented discussion is based on the elucidation of the effect of the substrate topography effect on the dewetting process through the excess of chemical potential. Finally, Raman analysis on the fabricated samples are presented. They show, in particular for the case of the Pd nanoparticles on FTO, a pronounced Raman signal enhancement imputable to plasmonic effects