Nanoparticle aggregation due to dewetting of sandwiched buffer layers

The deposition of Au onto thin condensed volatile buffer layers produces small clusters. Sublimation of the buffer converts these clusters into compact or ramified structures, depending on the thickness of the buffer, in a process called buffer-layer-assisted growth. We have used bilayer structures of Xe on CO2 or Xe on H2O on amorphous carbon substrates to investigate effects of second layer dewetting and the impact of the initial particle size on aggregation. Compact particles formed by Xe desorption aggregate during removal of the CO2 or H2O layer but little aggregation occurs for ramified particles produced on Xe layers thicker than ∼100 ML. Instead, the large structures tend to break up on the CO2 film, producing smaller, more compact particles. CO2 and H2O impurities in the Xe film significantly reduce particle coalescence and accelerate Xe dewetting.