Magnetic suppression of secondary electrons in plasma immersion ion implantation

In this work, magnetic suppression of secondary electrons in plasma immersion ion implantation is demonstrated experimentally in a vacuum arc system. Secondary electrons emitted normally to a copper sample surface were detected by a Faraday cup, whose signal exhibited large negative spikes coincident with high voltage pulses when aluminum ions of an unmagnetized plasma were implanted. When a 12.5 mT magnetic field parallel to the sample's surface is applied, these spikes are not seen, showing that secondary electrons were magnetically suppressed. Another cup, oriented to detect electrons that flow along the field lines, does not exhibit such negative spikes in either unmagnetized or magnetized plasmas, indicating that a virtual cathode was formed by the trapped secondary electrons