First-principles molecular-dynamics calculations and STM observations of dissociative adsorption of Cl2 and F2 on Si(0 0 1) surface

We have studied the dissociative adsorption process of halogen molecules (Cl2 and F2) on the Si(0 0 1) surface by first-principles molecular-dynamics (FPMD) calculations and scanning tunneling microscopy (STM) observations. From FPMD calculations, we demonstrate that Cl2 and F2 molecules adsorb dissociatively at dangling bonds of a buckled dimer with no energy barrier, so that the buckled dimer becomes geometrically flat. In addition, STM observations show that the dissociative adsorptions of Cl2 and F2 induce buckled dimers at the SA step on the Si(0 0 1)-(2×1) surface to become symmetric dimers, in good agreement with the results of FPMD calculations.