Temperature-induced processes for size-selected metallic nanoparticles on surfaces

The melting behavior of Iron-Nickel alloy nanoparticles on W(110) was studied under UHV conditions as a function of heating temperature and heating duration. These particles were found to be stable at 423 K without evaporation or diffusion taking place. Unrolling carpet behavior occurs at higher temperatures. This creates ramified islands around the nanoparticles. Ostwald ripening at higher temperatures or longer heating times is creating compact islands. The melting of these nanoparticles opens the possibility for thin film growth of FeNi alloys. The formation of monolayer high islands is a strong contrast to Fe, Co, and FeCo alloy nanoparticles which are dominated by direct evaporation, single atom surface diffusion and anisotropic spreading.