Secondary charged particles emitted from non-metallic surfaces under low-energy ion impact

Abstract

The secondary electron emission yields, γ −, and the secondary positive ion emission yields, γ +, from various non-metallic (perovskite type) targets induced by low-energy ion impact have been measured under ultra-high vacuum (∼10 −11 Torr) conditions. It has been found that the observed γ − from the non-metallic surfaces is proportional to the electronic stopping power over the whole impact energy range investigated. But the proportional coefficients in γ − are found to be 2–3 times larger than those for metal targets. We have observed, for the first time, that γ − strongly depends on the incident ion beam flux and becomes zero above a critical ion flux for some targets. We have also found that the observed γ + from non-metallic surfaces under Ar + ion impact is far large compared with the calculated results and, unexpectedly, is proportional to the electronic stopping power but not to the nuclear stopping power. Furthermore, it is shown that, under high incident ion fluxes, these emitted ions have large kinetic energy, almost comparable to the incident ion energy, which can be due to local charge-accumulation formed through the interactions with the incident ions on the non-metallic surfaces.