First principles studies of an Si tip on an Si(100)2 x 1 reconstructed surface

We present a systematic study of the interaction between a silicon tip and a reconstructed Si(100)2 x 1 surface by means of total energy calculations using density functional theory. We perform geometry optimization to obtain the reconstructed Si surface using the local density approximation and the generalized gradient approximation methods and compare our results with those obtained experimentally. We then study the effects of the tip of a scanning probe of an atomic force microscope (AFM) on the behaviour of atoms on the reconstructed surface when the tip translates at distances close to it. Our results show that at certain positions of the tip relative to the surface and depending on the direction of the scan, the Si dimer on the surface flips, resulting in a local reconstruction of the surface into p(2 x 2) or c(4 x 2) configurations. These configurations exhibit energies lower by 0.05 eV/dimer than the Si(100)2 x 1 structure.