STRUCTURE OF CHEMISORBED ACETYLENE ON THE SI(001)-(2X1) SURFACE AND THE EFFECT OF COADSORBED ATOMIC-HYDROGEN

The structure of chemisorbed acetylene on the Si(001)-(2 x 1) surface is investigated based on ab initio molecular-dynamics simulations acco rding to the Car-Parrinello method and within the local-density approx imation (LDA) to density-functional theory. The calculations reveal th at the Si-Si dimer bond is stable upon acetylene chemisorption resulti ng in the formation of a four-member disilacyclobutene ring. Coadsorpt ion of two hydrogen atoms together with the acetylene molecule onto th e Si-Si dimer bonds results in cleavage of the Si-Si bond and separati on of the two silicon atoms by a distance equal to the second-nearest neighbor distance in bulk crystalline silicon. (C) 1997 Elsevier Scien ce B.V.