Antiferromagnetic coupling between two adjacent dangling bonds on Si(001): Total-energy and force calculations

Abstract

Scanning tunneling microscopy experiments reported that desorption from the hydrogen- and halogen-terminated Si(001) surfaces exhibits frequently the two types of dangling-bond (DB) configurations. One is the intradimer configuration, where two DBs are within a single Si dimer, and the other is the interdimer configuration, where two DBs are on one side of two adjacent Si dimers. Our spin-polarized density-functional-theory calculations show that the intradimer configuration is nonmagnetic with a buckled-dimer geometry, while the interdimer configuration is antiferromagnetic with two adjacent symmetric dimers. In addition, we show that when the dissociative adsorption of hydrogen molecule occurs across the ends of two adjacent dimers on a clean Si(001) surface, such an antiferromagnetic coupling between two adjacent DBs still exists, thereby giving rise to a structural transformation from buckled to symmetric dimers.