Structural analysis of the Cu(100)-p(2×2)-Sn surface using low and medium energy ion scattering spectroscopies

The atomic structure of the Cu(100)-p(2 × 2)-Sn surface has been studied using medium energy ion scattering (MEIS), co-axial impact collision ion scattering spectroscopy (CAICISS), low energy electron diffraction (LEED), and Auger electron spectroscopy (AES). The complex p(2 × 2)-based LEED pattern with antiphase domains was observed at an estimated Sn coverage of 0.21 ML, confirmed with AES. The existence of subsurface Sn atoms was immediately ruled out by the lack of blocking dips in the MEIS Sn scattered yield, whereas the initial analysis of the CAICISS data ruled out the three overlayer models, allowing quantitative fitting to focus on the Cu-Sn substitutional surface alloy model. The fitted model showed that the surface relaxed outward following Sn deposition and also demonstrated an out-of-plane shift of Sn atoms in the outermost layer.