Atomic structure of two-dimensional binary surface alloys: Si(111)-root 21 x root 21 superstructure

Abstract

The atomic structures of Au and Ag co-adsorption-induced root 21 x root 21 superstructure on a Si(111) surface. i.e., (Si(111)-root 21 x root 21-(Au, Ag)), where the Si(111)-5 x 2-Au surface is used as a substrate, have been investigated using reflection high-energy positron diffraction (RHEPD) and photoemission spectroscopy. From core-level spectra, we determined the chemical environments of Ag and Au atoms present in the Si(111)-root 21 x root 21-(Au, Ag) surface. From the rocking curve and pattern analyses of RHEPD, we found that the atomic coordinates of the Au and Ag atoms were approximately the same as those of the Au and Ag atoms in other Si(111)-root 21 x root 21 surfaces with different stoichiometries. On the basis of the core-level and RHEPD results, we revealed the atomic structure of the Si(111)-root 21 x root 21-(Au, Ag) surface. (C) 2012 Elsevier B.V. All rights reserved.