Mitigation of charge injection in polyethylene films by silver nanoparticles/SiOxCy:H barrier layer: Dependence on the particles size and surface density

We have recently reported on the effect of silver nanoparticles plasma polymerized stack deposited on a polyethylene film preventing charge injection of both polarities under DC field. We investigate here the effects of the size and density of the silver nanograins on the barrier effect for charge injection. Size and density of the nanoparticles, and the surface coverage are controlled through the plasma process. A comparative study of space charge distribution between a reference polyethylene film and tailored films is presented in 300 μm-thick films using the pulsed-electroacoustic technique. It is shown that the barrier effect depends on the size distribution of the nanoparticles and surface coverage: 15 nm silver nanoparticles with a high surface density but still not percolating form an efficient barrier layer that suppress charge injection. It is worthy to note that charge injection is detected with an increasing intensity for percolating nanoparticles, for a semi-insulating layer without nanoparticles and for smaller size silver particles (<;10 nm). The mechanism of charge injection mitigation is discussed.