High‐Power Terahertz Emission from Picosecond Nano‐Plasma Switching Driven by Secondary Electron Emission Avalanche

V/m is required for SEEA initiation, which covers an ∼100 nm gap within ∼ 0.1 ps, switches the NPD on via ionization avalanche within ∼ 1 ps, and produces a 0.4 THz signal with 2 W power. The switching speed increases with higher pressure. Model-guided device optimization identified the high-secondary-emission-yield substrates that favor THz generation, and defined the optimum nanogap length range that ensures both discharge initiation and emission within the THz range. This work demonstrates NPD as a feasible and scalable design for watt-level, on-chip THz generation, and suggests possible future integration with triboelectric nanogenerators as well as potential implications for vacuum nanoelectronic platforms.