Influence of primary beam profile on LEIS spectra

Abstract

The importance of low energy ion scattering (LEIS) as a technique for surface characterization is in its low information depth. Serious problems concerning the quantitative analysis of the surface composition by means of LEIS are mainly associated with the neutralization phenomena during the interaction of low energy ions with surface atoms. It is known that intensities of quasi-single (QS) peaks in LEIS spectra depend on the experimental setup such as a detection system or an acceptance region of an energy analyzer. If the acceptance region of the analyzer is smaller than the spot size of the primary ion beam, QS peak intensities will depend on the primary ion beam profile. Therefore, a significant error can be made in quantitative characterization by means of relative sensitivity factors. In this paper, we study the influence of the beam profile on QS peak intensities obtained in LEIS experiments with a polycrystalline copper target. For this purpose, our LEIS experiment is modified in order to provide fast and simple determination of the primary ion beam profile during the measurement of the energy distributions of scattered ions. On the other hand, the acceptance region of the 127° cylindrical energy analyzer used in these experiments is calculated according to results of numerical simulations. The correlation between the experimental results and the calculated magnitudes of the acceptance region will be discussed.