In-flight modification of Ni nanoparticles by tubular magnetron sputtering. (11th March 2019) - Kretková, Tereza
Abstract: A tubular magnetron (TMG) was used for in-flight deposition of Cu over Ni nanoparticles (NPs) pre-synthesized in a planar magnetron-based gas aggregation cluster source. The amount of deposited copper was driven by the magnetron current and magnetic field of the TMG. The structure of the resultant NPs was investigated by transmission electron microscopy (TEM), scanning transmission electron microscopy, x-ray diffraction (XRD) and small angle x-ray scattering. Alloying of Cu and Ni was observed in all the cases, yet with the formation of a copper-enriched shell in the case with higher Cu content. XRD and TEM analyses showed that plasma-NP interactions led to the disappearance of Ni crystal lattice defects. For a certain range of the magnetron currents, spontaneous pulsing of the NPs deposition rate was observed which was accompanied by the changes in the NP size distribution and chemical composition. The phenomenon was attributed to the cycle trapping, growth and release of the NPs inside and from the TMG. Such cycle instabilities led to the formation of NP deposits with high polydispersity.