ATOMIC AND ELECTRONIC-STRUCTURES OF OXYGEN-ADSORBED SI(001)SURFACES

We investigated the stable structures of oxygen-adsorbed Si(001) surfa ces and their electronic states. For this study, the first-principles molecular dynamics method with the ultra-soft pseudo-potential scheme of Vanderbilt was applied. We found three (meta)stable sites for atomi c oxygen adsorption - a dimer bridge and two different back-bond sites . The back-bond site of the down dimer-atom is the most stable. Here, the original dimer bond is preserved and the stress of the back-bond i s released. The electronegativity of oxygen enhances the difference of ionicity between the dimer atoms. Further, it is shown that this oxyg en-adsorbed site can be identified using scanning tunneling microscopy .