First-principles molecular-dynamics calculations and STM observations of dissociative adsorption of Cl2 and F2 on Si(001) surface

We have studied the dissociative adsorption process of halogen Molecules (Cl-2 and F-2) 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 Cl-2 and F-2 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 Cl-2 and F-2 induce buckled dimers at the SA step on the Si(0 0 1)-(2 x 1) surface to become symmetric dimers, in good agreement with the results of FPMD calculations. (C) 2002 Elsevier Science B.V. All rights reserved.