Nano-particle size-dependent charging and electro-deposition in dielectric barrier discharges at atmospheric pressure for thin SiOx film deposition

This paper focuses on charging and electro-deposition of nano-particles produced in a mixture of silane and nitrous oxide diluted in N-2, by dielectric barrier discharge (DBD) at atmospheric pressure for SiOx film deposition. Townsend discharge (TD) and filamentary discharge (FD) are compared with and without SiH4. Without SiH4, particles are produced by filament-surface interaction. Both filament-surface and plasma-silane interactions lead to bimodal particle size distributions from nucleation and agglomeration. With SiH4, particle formation and growth imply the same mechanisms in TD and FD. Faster dynamics in FD are related to higher local volume energy density than in TD. From scanning electron microscope images of the film and measurements downstream of the DBD reactor, the diameter of the particle produced is below 50 nm. An analytical model of electro-collection in an ac electric field is used to investigate nano-particle charging. To account for selective electro-deposition leading to particles smaller than 50 nm being included in the layer and to particle size distribution measured downstream of the DBD, the same size-dependent charging and electro-deposition of particle are involved, with different charging dynamics in TD and FD.