First principles total energy calculations of the adsorption of single Cl₂ and Br₂ molecules on the Si(001)‐c(2 × 4) surface

Abstract

We have performed first principles total energy calculations to investigate the adsorption of Cl 2 and Br 2 molecules on the Si(001)-c(2 × 4) surface. First of all, our results indicate that the adsorption of Cl 2 and Br 2 as molecules is not energetically favorable. Instead, Cl 2 (Br 2 ) dissociates into two Cl (Br) subunits. The most stable geometry was achieved when each Cl (Br) subunit is bonded to a Si atom of the same Si dimer along the dangling bonds. Three other geometries were considered in our study: the first one corresponds to adsorption of the two subunits on Si dimer sites in adjacent silicon dimer rows. The second corresponds to adsorption of the two Cl (Br) subunits along dangling bonds of two consecutive dimers of the same Si dimer row, with the two Cl(Br) atoms in the same side of the Si dimer row. The third one is similar to the second, but the ad-atoms are now in a staggered arrangement, occupying sites in opposite sides of the Si dimer row. These are adsorption configurations that have been observed experimentally for Cl 2 on Si(001). Our results indicate that energetics and atomic geometries are similar for Cl 2 and Br 2 . We have also calculated energy barriers for the ad-atom to move along and across the Si dimer rows. It is found that the barriers for Br are smaller than the barriers for Cl. This result can explain the differences observed in the adsorption of Cl 2 and Br 2 molecules.

Cooperative Chiral Adsorption of Styrene Molecules on the Si(001)-c(2 × 4) Surface: First-Principles Investigation of Reaction Mechanisms

“…Dimer Si1–Si2's bond length is 2.41 Å, and dimer Si3–Si4's bond length is 2.47 Å. This asymmetric behavior has been previously observed in the adsorption of SiH 2 and GeH 2 on Si(001) surfaces. The distortion of the end-bridge structure is generally of Jahn–Teller type, enhancing the stability by the symmetry breaking, causing the dimer to be nonmetallic.…”