Multiscale simulation of hollow cathode assisted internal plasma treatment process

Hollow cathode discharges can be used for the plasma-assisted surface treatment and coating of the interior surface of blind hole geometries. Due to the geometry, it is difficult to find the setting parameters for a reproducible result. Therefore, a probabilistic simulation based on a Monte Carlo method has been performed to simulate a hollow cathode discharge in a blind hole with an aspect ratio ≫ 1. First, different neutral gas flows inside a blind hole geometry were investigated with a direct simulation Monte Carlo method and compared to impact pressure measurements. Then, the resulting neutral gas pressure distribution was used in a Particle-in-Cell plasma simulation as a background gas to determine the electrical potential distribution, the charge carrier distribution and mean energy inside the blind hole geometry. The plasma potential distribution is compared with a substrate coated with an amorphous diamond like carbon (a-C:H) thin film and shows good agreement.