Microplasma Formation Around a Microstructured Surface

In this work, we characterize the formation and transition behaviors of a microplasma around a microstructured surface at different gas pressures via two-dimensional particle-in-cell/Monte Carlo collision simulations. It is found that the microdischarge occurs outside the cathode microcavities at the lowest pressure and starts penetrating the microcavities with a curved sheath edge as the pressure increases. At higher pressure, coupled periodic microhollow cathode discharges (MHCDs) are formed inside the microcavities. Further increasing the gas pressure results in the disappearance of the MHCDs, and the dominant discharge shifts outside of the microcavity, locating above the protrusion tips. The effect of the space charge shielding on the discharge and the conditions for MHCD formation are discussed. The macroscopic discharge parameters versus the gas pressure and the electron energy distributions are examined. The results are helpful for better understanding the microplasma formation around nonplanar electrode surface in microgaps, which inform the scaling, design, and optimization of microplasma array devices across a wide range of gas pressure regimes.