Surface composition analysis by low-energy ion scattering

Study of preferential sputtering and segregation effects on the surface composition of AlPdMn quasi‐crystals

“…This composition is surface enriched in Al so it is also consistent with the surface energies ranging from lowest to highest in the order from Al to Mn to Pd [9] In the following analysis yield ratios were corrected for cross-section differences, but no change was made on the basis of a difference in charge fraction. [1,10] Ion bombardment of this surface resulted in a significant decrease in Al and an increase in Mn at the surface (Fig. 1).…”

LEIS: A reliable tool for surface composition analysis?

“…This enhancement of backscattered intensity and its interplay with CIR and ineffective AN leads to the observed increase in P + due to reionization in a final large angle scattering process that may occur in or close to the surface [1]. This interpretation becomes more obvious when plotting the data as a function of α instead of 1/v ⊥ (see Fig.…”

“…Consequently, a TOF-spectrum recorded for a single crystal under these conditions allows to determine the ion fraction P + from a direct comparison of the ion peak A + and the surface peak of neutrals A 0 , since they are formed by particles backscattered in a single collision from the surface layers [ 15], [ 16 ]. Different detection efficiencies for ions and neutrals must be taken into account (see Fig.1) [1].…”

“…The LEIS technique is thought to be extremely surface sensitive: this is partially because of the high scattering cross section but especially due to very effective neutralization which assures the signal to originate from the outermost atomic layers only [ 1]. Qualitative understanding of the underlying processes is available and necessary but not sufficient to obtain quantitative information on the surface composition.…”

“…In the collision between the projectile and a target atom, a minimum distance smaller than R min is reached if for a fixed scattering angle θ − the projectile energy E exceeds a certain threshold E th . The specific value of E th depends on the atomic species of the collision partners and on the scattering angle θ; e.g., for He + scattered from Cu and θ =129°, E th = 2100 eV [1]. For E > E th , P + is therefore not a unique function of v ⊥ , since for a given projectiletarget atom combination the probabilities for the collision induced processes, P CIN and P CIR , depend on E and θ instead of v ⊥ .…”