Nanometer-level self-aggregation and three-dimensional growth of copper nanoparticles under dielectric barrier discharge at atmospheric pressure

We have recently demonstrated an approach to the surface activation of fluoropolymers, based on the plasma-induced decomposition and reduction of an organo-copper precursor. Although a surface densely and homogeneously seeded with copper nanoparticles enables the initiation of the autocatalytic electroless deposition of a copper layer at 40 °C with a time lag of less than 2 s, the formation mechanism of Cu nanoparticles under this plasma process is yet to be elucidated. Here we report some progress on this matter: scanning electron, and atomic force microscopic experiments revealed that the total population of Cu nanoparticles on the surface clearly decreased with time while the particles continued to grow. Furthermore, their growth behavior strongly depended on the plasma intensity. These results imply that the thermodynamically driven spontaneous migration of Cu atoms occurred from the initially formed smaller particles to the larger ones by the Ostwald ripening mechanism.