Heavy-ion-induced secondary electron emission from magnesium, aluminium and silicon partially covered with oxygen

Abstract

We bombarded magnesium, aluminium and silicon with 80 keV Ar + ions and measured the secondary electron emission yields at projectile incidence angles from 0° to 85° with oxygen present at the target as well as under ultrahigh vacuum conditions. The total secondary electron emission yields were found to depend markedly on the amount of oxygen present. The three elements studied show relatively large individual variations. For all three elements, and with as well as without oxygen present, the relative secondary electron emission yield was observed to vary as 1/cos v where v is the angle of incidence of the projectiles. This seems to indicate that the secondary electron production is initiated uniformly along the projectile path in the solid, in a region close to the surface. The results are discussed, and it is tentatively suggested that the increase in secondary electron emission caused by the presence of oxygen originates from electron loss from sputtered oxygen which initially is present as O 2− ions.