Electrostatic charging effects in fast H+ interactions with thin Ar films

We have studied electron emission, luminescence and sputtering from thin Ar films excited by 2 MeV protons. We varied the voltage, Va, of the anode surrounding the target, which extracts electrons from the film and results in unbalanced positive charges. The resulting large internal electric fields alter sputtering and luminescence. At the beginning of irradiation of a freshly deposited film, we observe that a positive anode voltage of a few hundred volts produces a large, catastrophic increase in sputtering which gradually disappears as irradiation progresses. We discuss the results in terms of dielectric breakdown induced by macroscopic charging associated with deep charged defect sites