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, GHrAu and Si02 surfaces at impact of slow (v= 0.3 v-) ions has been measured as a finction of incident ion charge for l+<q<75+. Electron yields from thermal silicon dioxide films (150 nm on Si) are found to be lower than those from Au and &HY-Au for q>3+. Yields of negative secondary ions from Si02 and CHY-AUwere recorded in parallel with electron emission data and exhibit a q", n=l, dependency on incident ion charge. A direct comparison of collisional and electronic contributions to secondary ion production from Si02 films using abeam of charge state equilibrated Xe-(at 2.75 keV/u) shows positive and negative secondary ion yield increases with incident ion charge of >400. Results are dkcussed in relation to key signatures of electronic sputtering by Coulomb explosions.

Electronic sputtering of solids by slow, highly charged ions: Fundamentals and applications

“…Secondary ion yields from GaAs and UO 2 samples were measured by time-of-flight secondary ion mass spectrometry with SHCI as projectiles [15][16][17][18]. in negative polarity and >80% in positive polarity for SHCI like Xe 44+ .…”

“…The finding of secondary ion intensities in the order of 0.1 to 5 secondary ions detected per SHCI [15] stimulated interest in the development of SHCI based surface analysis in a time-of-flight secondary ion mass spectrometry scheme [16][17][18]. Secondary ion production was found to be dominated by the projectile charge and largely independent of projectile velocity [13,15].…”

“…Secondary ion production was found to be dominated by the projectile charge and largely independent of projectile velocity [13,15]. The detection of more than one secondary ion from one impact event with high enough (>0.01) probability allows for the analysis of correlations in secondary ion emission.…”

Possible diamond-like nanoscale structures induced by slow highly-charged ions on graphite (HOPG)

“…The neutralisation process of the SHCI is extremely fast, of the order of a few femtoseconds, during which a surface domain with high ionisation density is formed. As electrons from the surrounding solid cannot replace promptly the removed electrons, the impact area cannot be neutralised within time scales of less than several picoseconds, and the localised charged region can suffer a Coulomb explosion, forming in this manner surface defects at the nanoscale level 6,7,8 . Such nanometer-size defects ranging between 3nm to 50nm have been observed in the form of craters or blisters in materials such as silicon 9 , mica 10 , highly-oriented pyrolytic graphite 11 , SiO 2 and Al 2 O 3 12 using atomic-force microscopy (AFM) and scanning tunnelling microscopy (STM).…”

Surface charge compensation for a highly charged ion emission microscope

“…This kinetic transfer is a multistep, relatively low cross section process that is distributed across a comparatively deep collision and is not localized to the surface layers. The localized energy deposition from a HCI/surface interaction results in very high (100s of electrons per primary ion) electron 6,7 and (greater than one) secondary ion yields 8 . The ratio of the secondary ion yield to the secondary neutral yield gives ionization probabilities of 10% for HCI excitation 9 .…”