Origin of the buckling in thec(2×2)-Si/Cu(110) surface alloy

Abstract

The atomic structure of the $c(2\mathrm{}\times 2)$-Si/Cu(110) interface has been determined by angle scanned photoelectron diffraction at several electron kinetic energies using synchrotron radiation and by quantitative low-energy electron diffraction (LEED) studies. Experimental photoelectron diffraction scans and LEED $I/V$ curves have been compared through $r$-factor minimization with single and multiple scattering calculations in order to determine an atomic model for the surface termination. Both techniques show that the $c(2\mathrm{}\times 2)$ superstructure is originated by a two-dimensional alloy in which the Si atoms occupy substitutional Cu sites at the surface layer, with a topmost Si layer vertically displaced inward by $0.26\pm 0.04\AA .$ A possible mechanism for the origin of the corrugation based on a strong chemical bonding between the Si deposited atoms is proposed.