Stable site and stable charge state of a fluorine atom in Si

We investigated a stable state of a fluorine (F) atom in Si bulk by using first-principles calculations. We considered various interstitial sites and three charge states from +1 to -1. We found that over a wide range of Fermi levels, the bond center site in the +1 charge state is the most stable for an F atom. The present calculations suggest that the experimentally observed conductivity-dependent etching properties of F for Si are intimately related to the charge-state-dependent stable site of F in the Si bulk.