Dynamics and Energetics of Reconstruction at the Si(100) Surface

In experiments the reconstructed Si(100) surface shows silicon dimers pointing along the [011] direction. However, the origin of the dimer formation is still unclear. Our theoretical studies on dynamics and energetics show that the reconstruction process depends crucially on the initial local surface morphology: starting from different local tilting scenarios various reconstruction domains can appear as a result of thermal excitation. Molecular dynamics simulations show that c(4 × 2) and asymmetric p(2 × 1) reconstructions can appear quite easily while p(2 × 2) domains are less likely to be found even though they are energetically favorable. The latter is consistent with experimental findings of p(2 × 2) domains being observed quite rarely. The simulations show further that spontaneous dimer-flipping in asymmetric p(2 × 1) domains is possible at about 100 K and driven by the stress within the aligned atoms below the tilted dimers. This can result in a transition to c(4 × 2) reconstruction which is consistent with this reconstruction dominating in experiments above 80 K