Chemisorption of Co monolayer on H-passivated Si(1Â 1Â 1) surface: Comparison with clean Si(1Â 1Â 1) surface

The chemisorption of Co monolayer on H-passivated Si(1 1 1) surface was studied theoretically using tight binding linear muffin-tin orbital (TB-LMTO) method and compared with that of the clean Si(1 1 1) surface. For the clean Si(1 1 1) surface, Co atoms prefer to adsorb on the interstitial center site and might even sit below the Si surface, forming a Co-Si mixed layer at the interface. On the contrary, for the H-passivated Si(1 1 1) surface, the energetically favorable position for the Co adsorption is at the top site and Co atoms cannot adsorb below the H layer or diffuse into the lattice. The present results indicate that the H passivation layer effectively hinders intermixing between Co and Si atoms.