Numerical simulation of breakdown characteristics of capacitively coupled hollow cathode discharge

Hollow cathode discharge (HCD) is widely applied in processes like chemical vapor deposition due to its unique cavity structure that enhances ionization, plasma density, and sputtering via the hollow cathode effect (HCE). While discharge characteristics have been studied extensively, most work focuses on the steady-state phase, investigating groove geometry, cavity number, and power supply (Luo et al. 2024; Wang et al. 2021). In contrast, studies on the breakdown phase mainly address conditions for ignition, with limited insight into the temporal evolution of plasma properties.

In this work, a 2D Particle-in-cell/Monte Carlo collision (PIC/MCC) simulation is developed to investigate the breakdown process of radio-frequency HCD. Results show that during breakdown, the electron density inside the groove is significantly higher than in the main chamber, with the density peak appearing at the center of the electrode opposite the groove. After the breakdown, the electron density peak shifts to the outer side of the groove. Before the breakdown, the electron energy is uniformly distributed with relatively high energy throughout the bulk region; as the breakdown progresses, the energy decreases and becomes concentrated outside the groove. The evolution of other plasma parameters, including the electric field, potential, and particle distributions, electrical characteristics such as the evolution of impedance and capacitance, is also analyzed.