Numerical investigation of the film uniformity during the surface coating of charged nanoparticles in a low pressure plasma reactor

• The surface coating of charged nanoparticles in a low pressure plasma is investigated by numerical simulation of the multi-fluid plasma equations.
• The deposition rate on the particle surface is not spatially uniform.
• The nonuniformity in the film deposition is attributed to the anisotropy of the ion flux.
• The nonuniformity increases with distance from the sheath edge.

The uniformity of film deposition on charged nanoparticles, trapped near the sheath of a capacitively coupled plasma reactor, is studied by numerical simulation of the multi-fluid plasma equations, surface deposition processes, and nanoparticle heating effects. It is found that the anisotropy in the ion flux onto the powered electrode may be hold responsible for the film nonuniformity. The nonuniformity increases with increasing of the particle radius, although small particles lose sphericity faster than the large particles. Because of the electron temperature dependence of the deposition rate and the incident ion flux, higher electron temperatures lead to more nonuniform film deposition. However, the uniformity is improved and the sphericity is restored by the increase in the background gas pressure and/or temperature.