Dimer rotation on the carbon-induced Si (001) -c (4×4) structure

Abstract

We present first-principles results identifying the reaction pathways for Si dimer rotations on the carbon-induced Si (001) -c (4×4) surface. The nudged elastic band calculations show that the recently proposed rotated dimer model [Phys. Rev. Lett. 94, 076102 (2005)] can be obtained from the refined missing dimer model by dimer rotation with small energy barriers. It is found that the energy barrier is sensitive to the rotation directions of Si dimers. The energy barrier along the minimum energy path (MEP) is 0.82 eV. Three stable configurations are identified along the MEP, one of which with a single rotated dimer is more stable than all existing models and its energy is lower than that of the rotated dimer model, the previously most stable structure, by 0.25 eV per c (4×4) cell. The stabilization mechanism of the new stable structure is analyzed. We propose a possible method to search for new stable structures based on the existing models by mapping out the reaction paths in the phase configuration. © 2006 The American Physical Society.