Structural and electronic properties of(32×2)R45°-Sn/Cu(100): Density functional theory and scanning tunneling microscopy

Abstract

The structural and electronic properties of the $(3\sqrt{2}\ifmmode\times\else\texttimes\fi{}\sqrt{2})R45\ifmmode^\circ\else\textdegree\fi{}$ phase of 0.5 monolayers of Sn on Cu(100) have been investigated using a combination of scanning tunneling microscopy experiments and total-energy-minimization calculations. Theory and experiment support the missing-row surface-alloy structure as the ground state for this surface [K. Pussi, E. Al Shamaileh, E. McLoughin, A. A. Cafolla, and M. Lindroos, Surf. Sci. 549, 24 (2004)]. The calculated electronic structure reproduces almost perfectly both the experimental scanning tunneling microscopy images and the observed electronic bands. Our results conclusively indicate that the creation of Cu vacancies in the top surface layer produces a significant reduction of the total energy. We also report a metastable $(3\sqrt{2}\ifmmode\times\else\texttimes\fi{}\sqrt{2})R45\ifmmode^\circ\else\textdegree\fi{}$ phase coexisting with the ground state at room temperature, which we attribute to a two-missing-row surface-alloy structure.