Element-, velocity- and spatially resolved images of Kr + scattering and recoiling from a CdS surface

Abstract

Developments in ion scattering spectrometry and detector technology allow measurement of element-, velocity- and spatially resolved distribution patterns of scattered and recoiled atoms, forming the basis for a scattering and recoiling imaging spectrometry (SARIS). SARIS images are architectural fingerprints of surface short-range order. They exhibit extreme sensitivity to structural details, providing a unique probe for determination of surface composition and structure. Quantitative analysis is obtained by comparison with simulated images using the scattering and recoiling imaging code (SARIC). The SARIS technique is demonstrated herein for analysis of the composition and termination of a CdS (0001) surface. Using 4 keV Kr + primary ions, it is possible to observe separate images of Kr scattering from Cd and images of recoiled H, O, S and Cd atoms. The O and H atoms are impurities which are observed on this surface, even after annealing to 700°C. It is found that the Cd-terminated surface contains Cd atoms in the first layer and S atoms in the second layer. The surface structure appears to be stabilized by bonding of the first-layer Cd atoms to O or OH moieties.