Coalescence of palladium nanoparticles assembled on carbon and SiC surfaces: STM and STS studies

Pd nanoparticles assembled on carbon and carbon-terminated SiC substrates were prepared by reducing palladium ions in one step chemical reduction technique. Morphology, size distribution and coalescence of the nanoparticles were studied by scanning tunneling microscopy (STM). Smaller nanoparticles and higher coalescence events were observed for carbon substrates. The formation of Pd(1 1 1) terraces by coalescence of the nanoparticles was observed. Atomic diffusion induced by ambient exposure is proposed to explain the coalescence of the nanoparticles at the step edges of the Pd(1 1 1). Scanning tunneling spectroscopy (STS) results revealed the metallic contact between the nanoparticles and the absence of a tick non-metallic layer of residual impurities on the nanoparticle surface.