Controlled Switching of Stationary Surface Silicon Dimers

Dimer pairs of the unterminated Si(100)-2x1 surface undergo an energy lowering lattice distortion. In this ground state, the Si dimer buckles, causing one atom to lower while the other is raised. This buckling phenomenon disappears when the surface is terminated with a hydrogen monolayer. Selectively removing pairs of H atoms that belong to Si dimers causes the dimer buckling to return. STM imaging of dimer structures at high biases allow us to observe them in a dynamic regime where dimers rapidly switch between buckled configurations. At very low biases, however, we enter the static regime where the buckling of dimers remains fixed. Furthermore, STM pulses on dimer structures enables for the controlled flipping of the buckled dimer orientation. We explore the underlying physics behind this and their possible applications.