Microscopic evolution mechanism of streamer-like pulses in silicon needle corona discharge based on plasma chemistry

Under negative DC corona with a silicon needle cathode, the discharge phenomenon differs markedly from that of metal electrodes, producing “streamer-like pulses” that exhibit significant randomness. To elucidate the formation mechanism, a two-dimensional axisymmetric pin–plate discharge model based on plasma chemical reactions was established to systematically investigate the kinetic processes and microscopic mechanisms of the silicon needle corona discharge. Compared with small-amplitude pulses, the formation of streamer-like pulses involves substantially higher electron density, electric field intensity, and ion density. The electron distribution is localized within 0.1 mm in front of the needle tip, with a pronounced electric field depression occurring in the region 0.01 − 0.1 mm from the tip. Ion composition analysis reveals that at the peak of small pulses, the dominant positive ions are O4+ and O2+, and negative ions are primarily O2−, whereas at the peak of streamer-like pulses, N4+ and O2+ become the dominant positive ions. Surface conductivity modulates the discharge mode: low conductivity gives large amplitude disparity, whereas high conductivity yields uniform pulses. Although photoionization is enhanced during streamer-like pulses, collisional ionization remains the main source of electron multiplication. This study reveals the synergistic regulation mechanism of silicon needle surface properties and space charge on discharge modes, providing a theoretical basis for understanding corona discharge behaviors on semiconductor electrodes.