DescriptionLow Energy Ion Scattering (LEIS) is a surface analysis technique with extremely low information depth, normally only a topmost atomic layer. Extreme surface sensitivity is given by very efficient neutralization processes of He+ ions with energies below 8 keV. The downside of this is the dependence of the signal on the details of neutralization processes, which can cause matrix effects. In this work we report several previously unknown matrix effects in LEIS from surfaces composed of Ru-B, Ru-C and Ru-O material combinations. Measurements with variable ion energies prove that characteristic velocities of involved elements change with surface composition. We suggest that the neutralization channel responsible for these matrix effects is quasiresonant neutralization from the valence band (VB-qRN). VB-qRN is present in elemental C and B due to a wide valence band with energy states as low as -20 eV, where it comes in (quasi-)resonance with the He 1s level. This mechanism was earlier reported for graphitic carbon and nickel oxide. We believe that it can be applied to a much wider range of materials, leading to potential matrix effects in LEIS from a variety of surfaces, containing B, C and O atoms, e.g. borides, carbides and oxides, as well as alloys with B and C. On example of Ru-B system we demonstrate that quantification of surface composition can still be achieved if changes in band structure are consistent.
|Period||1 Jul 2018 → 6 Jul 2018|
|Event title||28th International Conference on Atomic Collisions in Solids & 10th International Symposium on Swift Heavy Ions in Matter|
|Degree of Recognition||International|