Density functional theory calculations were made of electric-field effects upon a clean Si(001) surface, and of the diffusion of Si or Ge adatoms on Si(001) surfaces. The results indicated that the electric field only slightly affected the dimer bond-lengths and buckling-angles of clean Si(001); thus implying that the electric field of a scanning tunnelling microscopy tip could not be responsible for the observation of symmetrical dimers and the flip-flop motion of buckling dimers. The electric field mainly influenced diffusion along the dimer row, and the diffusion barrier could be greatly reduced under a positive electric field. It was expected that a positive field would make the diffusion of Si or Ge adatoms on the Si(001) surface more anisotropic.

Electric-Field Effects on the Diffusion of Si and Ge Adatoms on Si(001) Studied by Density Functional Simulations. Y.He, J.G.Che: Physical Review B, 2009, 79[23], 235430