Mechanism of the short range ordering in a 2D binary alloy

Direct comparison of scanning tunneling microscopy (STM) and high-resolution core level photo-emission experiments provides a rationale for the mechanism of short range ordering in a two-dimensional (2D) binary alloy (1/3 monolayer (ML) Sn(1-x)Six/Si(1 1 1)-(root3 x root3)R30degrees). The host pure Sn metal surface (x = 0) results partitioned into two classes (2/9 and 1/9 ML) of ad-atoms occupying non-equivalent T-4 Sites. Sn substitution with Si ad-atoms preferentially takes place at the majority type adsorption sites. This occurrence explains the atomic intermixing and the short range ordering directly observed with STM and typical of a wide class of 2D binary alloys. (C) 2002 Elsevier Science B.V. All rights reserved.