Slow-particle-induced kinetic electron emission from a clean metal surface: A comparison for neutral and ionized projectiles

The influence of projectile charge state on ionization probabilities of sputtered atoms

“…4, it also appears to slightly increase with increasing impact energy. These findings are similar to those made for both external [9] and internal [6] electron emission yields. In both cases, a lower electron yield was found under bombardment with neutral projectiles.…”

“…Comparing neutral and singly ionized Argon projectiles, on the other hand, it was found that the difference in electron emission yields is induced by the kinetics of the interaction rather than the ionization energy of the projectile [6,9]. One possible scenario behind this is that at sufficiently large impact velocities the impinging ion may survive above-surface neutralization and retain its charge state while penetrating through the first few monolayers below the surface, thereby experiencing a larger electronic stopping power than its neutral counterpart [9].…”

“…This question is addressed in the work presented here. Similar to the work on electron emission [6,9], neutral and singly positively charged Argon atoms are used as projectiles bombarding a metal surface, and the resulting ionization probability of the sputtered atoms is measured. The results are compared with predictions of model calculations of kinetic electronic excitation.…”

Electron emission following the interaction of slow highly charged ions with solids

“…The charge exchange and electron emission associated with the interaction of highly-charged ions with solid surfaces can be caused by one of two processes: (1) kinetic electron emission, or (2) potential electron emission. Kinetic electron emission is the direct result of the impact of the projectile on the surface and can be observed whenever the available energy is greater than the minimum energy required to remove an electron from the surface (Lakits, Arnau, Winter 1990). This will occur when the approach velocity is greater than about 10 7 cm/s.…”

“…Potential electron emission is a result of the charge of the approaching ion interacting with the surface. Potential emission is significant only if the potential energy of the approaching ion exceeds two times the work function of the surface (Lakits, Arnau, Winter 1990). Potential electron emission yields generally increase with the potential energy W carried by a highly-charged ion X q+ (Kurz et al 1994), and for projectile velocities v p < 2 x 10 8 cm/s kinetic electron emission yields generally decrease with decreasing v p (Kurz et al 1994).…”