The formation and dynamics of Pt-Si liquid droplets on Si (001) substrates have been investigated by Photo-electron Emission Microscopy (PEEM). After ambient deposition of a 10nm Pt film, a uniform PtSi layer was transformed into an island structure at approx 800 deg C. The PtSi islands of micrometer size began to melt and were transformed into molten Pt-Si alloy islands below the melting point of PtSi. At approx 1100 deg C surface migration of the micro-droplets was observed. The moving droplets coalesced with nearby islands and grew in size. The motion was related to the temperature difference across the substrate, and droplet migration was observed from the cold to the hot regions of the surface. The migration velocity was measured as a function of temperature and droplet size. The driving force for migration is related to material diffusion, equilibrium at the solid-liquid interfaces, and surface energetics.
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