Experimental Characterization of Low Voltage Field Emission From Carbon-Based Cathodes in Atmospheric Air

Nanoscale carbon-based field-emitter materials exhibit excellent electron field emission properties, characterized by low turn-on voltages and high current densities. The use of these materials has not been previously considered for ion generation in air, yet these properties suggest that substantial ionization may occur at low voltages compared to conventional methods involving glow or arc gas discharges. Electron field emission from carbon-based materials, including polycrystalline diamond and carbon nanotubes, in atmospheric pressure air is experimentally characterized. Electric fields between 30 V/μm and 100 V/μm applied between the two terminals produce field-emitted electrons via quantum tunneling. These electrons then travel through the electric field colliding with neutral air molecules and occasionally ionizing them. This process can produce a self-sustained current flow (from fractions of picoamperes to microamperes) between the anode and cathode. The current remains stable at voltages lower than those predicted by Paschen’s curve for gaseous breakdown and ionization. Results indicate the presence of field emission from the cathode that aids in sustaining current at low voltages. The observed behavior suggests that this method can achieve efficient generation of ions for air purification and ionic flow pumping.