Theoretical prediction of the antiferromagnetic ground state of a C defect on Si(001)

Abstract

We have performed first-principles density-functional calculations for the C defect on Si(001), which has been experimentally identified in terms of the dissociative adsorption of a single water molecule on two adjacent dimers. Unlike the hitherto accepted nonmagnetic structure that involves the buckling of two Si dangling bonds (DBs) within the C defect, the presently proposed structure shows that the two DBs are antiferromagnetically coupled with each other, thereby giving rise to a suppression of their buckling. This antiferromagnetic ground state of C defect reproduces the key features observed in the STM and STS experiments.