Microstructure of sputter deposited thin film for magneto optical recording media is well known for the relationship with media noise.
Fast and accurate deposition thickness control using sputtering has been normal production method for optical storage media.
Electrode of sputter accelerate argon ion to the deposition target. Particles out of the target might be called as argo-particle in analogy with photoelectron.
Tuning argon pressure in vacuum environment gives low noise media for a specific light source.