Nanoparticle Retention in Ambipolar Electric Field

Theoretical study of nanoparticle confinement by ambipolar field in RF capacitively coupled plasma are carried out for the case of vertically arranged electrodes. An analytical model of ambipolar diffusion in a plasma consisting of positive ions, electrons, and nanoparticles has been developed. The maximum size of nanoparticles that can be trapped is calculated depending on the nanoparticle density. At a low nanoparticle density, an ambipolar electric field can retain particles up to few micrometers in size. On the contrary, in the case of high nanoparticle density, the ambipolar electric field is significantly reduced and can only hold particles with a diameter of no more than a few hundred nanometers.