The isomeric effect on the adjacent Si dimer didechlorination of trans and iso-dichloroethylene on Si(100)-2×1.

The dechlorination processes of isomers trans and iso-dichloroethylene (iso-DCE) on Si(100)-2×1 were investigated from first principles, to ascertain the isomeric effect on the adjacent Si dimer di-dechlorination of DCE on Si(100)-2×1. By comparing the feasible adspecies and their reaction barriers between trans and cis-DCE on Si(100)-2×1, we found that the isomeric effect of trans-DCE is negligible, which explained the similar C 1s peak locations in the X-ray photoelectron spectroscopy (XPS) experiment. In contrast, iso-DCE undergoes a more complicated reaction process, although the adjacent Si dimer di-dechlorination is still the dominant mechanism. Among the initial competitive reactions involving intra-, inter-cycloaddition and single C-Cl cleavage, the barrierless intra-cycloaddition is the most favorable reaction and precludes the single dechlorination that yields the mono-σ structure. Subsequent di-dechlorination undergoes a three-step reaction to yield the final product intra-dimer tetra-σ. In addition, the ionization energies of C 1s and Cl 2s electrons were calculated for the tentative assignment of the peaks observed in XPS.