Real-space ion scattering maps of the Mg(0001) surface

Abstract

Low-energy ion scattering (LEIS) is useful for examining the structure of ordered surfaces as well as for identifying surface atoms. However, in some cases the structural information from LEIS measurements is obscured by complex collision processes which contribute to the detected scattering intensity. In this study, we have developed a more precise approach for examining surface structure that includes comparing experimental real-space ion scattering maps with simulations from binary collision codes using reliability factors. This method is demonstrated with the model system 2 keV ${\text{Ne}}^{+}\ensuremath{\rightarrow}\text{Mg}(0001)$. Using an angle-resolved ion energy spectrometer, the intensity of scattered ${\text{Ne}}^{+}$ from the surface was recorded for a complete set of polar and azimuthal angles, which define the orientation of the surface with respect to the incident beam. These angles were then transformed to distances in real space and used to compile an ion scattering map of the Mg(0001) surface. A simulated map was also generated for the same conditions using a modified version of the binary collision code MARLOWE. The maps provide a comprehensive overview of surface scattering and allow the locations of surface atoms to be correlated directly to regions of enhanced scattering intensity. The sensitivity of the LEIS signal to interatomic spacing was simulated using MARLOWE, and methods for comparing with experiments were developed. Because LEIS can distinguish different types of atoms on the surface, the techniques described here could be extended to map compound surfaces and adsorbates.