Emission of secondary particles from metals and insulators at impact of slow highly charged ions

Abstract

The emission of secondary electrons and ions from clean Au, C x H y Au and SiO 2 surfaces at impact of slow ( v ≈ 0.3 v Bohr) ions has been measured as a function of incident ion charge for 1 + ≤ q ≤ 75 +. Electron yields from thermal silicon dioxide films (150 nm on Si) are found to be lower than those from Au and C x H y Au for q > 3 +. Yields of negative secondary ions from SiO 2 and C x H y Au were recorded in parallel with electron emission data and exhibit a q n , n ≈ 4, dependency on incident ion charge. A direct comparison of collisional and electronic contributions to secondary ion production from SiO 2 films using a beam of charge state equilibrated Xe q= qeq (at 2.75 keV/u) shows positive and negative secondary ion yield increases with incident ion charge of > 400. Results are discussed in relation to key signatures of electronic sputtering by Coulomb explosions.