Abstract: The present invention discloses a structure of an emitter electrode for enhancing ion currents, including a tip end part and a shank part. The tip end part has a pinpoint, a first diameter, and a radius of curvature. A length of the tip end part with the shank part is from the pinpoint to a first position of the shank part and a distance between the first position and the pinpoint is 300 times the first diameter. The radius of curvature of the tip end part ranges from 50 nanometers to 5 micrometers. The first diameter is 2 times the radius of curvature.