Origin of p(2 x 1) phase on Si(001) by noncontact atomic force microscopy at 5 k -: art. no. 106104

The controversial issue of the origin of the p(2x1) reconstruction of the Si(001) surface observed in recent low temperature scanning tunneling microscopy experiments is clarified here using 5 K noncontact atomic force microscopy. The c(4x2) phase is observed at separations corresponding to weak tip-surface interactions, confirming that it is the ground state of the surface. At larger frequency shifts the p(2x1) phase of symmetric dimers is observed. By studying the interaction of a reactive Si tip with the c(4x2) Si(001) surface using an ab initio method, we find that the observed change in the surface reconstruction is an apparent effect caused by tip induced dimer flipping resulting in a modification of the surface structure and appearance of the p(2x1) phase in the image. Using an appropriate scanning protocol, one can manipulate the surface reconstruction at will, which has significance in nanotechnology.