Two-Dimensional Carbon Incorporation into Si(001): C Amount and Structure of Si(001)-c(4x4)

Abstract

The C amount and the structure of the Si001-c4 4 surface is studied using scanning tunneling microscopy (STM) and ab initio calculations. The c4 4 phase is found to contain 1=8 monolayer C (1 C atom in each primitive unit cell). From the C amount and the symmetry of high-resolution STM images, it is inferred that the C atoms substitute the fourth-layer site below the dimer row. We construct a structure model relying on ab initio energetics and STM simulations. Each C atom induces an on-site dimer vacancy and two adjacent rotated dimers on the same dimer row. The c4 4 phase constitutes the subsurface Si0:875C0:125 layer with two-dimensionally ordered C atoms.