The array of In-Bi heterodimers on the Si(100) surface

Abstract

Studying the In and Bi coadsorption onto the Si(100) surface at elevated temperatures using Scanning Tunneling Microscopy, Angle-Resolved Photoelectron Spectroscopy, and Density Functional Theory, we have found the formation of a 2 × 4 array of In-Bi heterogeneous dimers. The surface is closely related to a Bi-induced Si(100)2 × n-Bi (n=5−12) reconstruction and can be visualized as that with one Bi atom in a Bi-Bi dimer replaced by In atom, and the length of dimer rows stabilized on 4 periods. The In-Bi dimers are buckled, with Bi atoms being 0.62 Å higher than In. STM simulations revealed that the contribution of a Bi atom into experimental STM contrast is dominant. The asymmetric In-Bi heterodimers orient in a unit cell independent of each other producing chaotically looking STM images despite the 2 × 4 lattice itself is well-ordered. The surface is semiconductor featuring noticeable Rashba-type spin-splitting of surface states. This structure is believed to be an interesting object for theoretical and experimental studies on the influence of lack of symmetry and chemical disorder to spin polarization in the low-dimensional materials.