Theoretical investigations of adsorption of fluorine atoms on the Si(001) surface

First-principles pseudopotential total-energy calculations have been performed in order to investigate the initial adsorption of an F atom on the Si(001) surface, the structures of ordered fluorinated surfaces, and their stability against disordering. We have found that the F atom has a high adsorption energy and a high diffusion barrier on the Si(001) surface, and at high F coverage the defected surface containing SiF3 species which is regarded as a precursor for etching is stabilized compared with the ordered surfaces. The thermodynamical instability of the ordered surfaces against local facet formation does not occur at any F coverage. Our results indicate that the disordering of the fluorinated Si(001) surface, which occurs even at low F coverage, may be kinetically induced by the local heating due to the F adsorption.