| Abstract
| - The potential energy surfaces of one, two, and three water molecule sequential adsorptions on the symmetricallychlorinated Si(100)-2 × 1 surface were theoretically explored with SIMOMM:MP2/6-31G(d). The first watermolecule adsorption to the surface dimer requires a higher reaction barrier than the subsequent second watermolecule adsorption. The lone pair electrons of the incoming water molecule nucleophilically attack the surfaceSi atom to which the leaving Cl group is bonded, yielding an SN2 type transition state. At the same time, theCl abstracts the H atom of the incoming water molecule, forming a unique four-membered ring conformation.The second water molecule adsorption to the same surface dimer requires a much lower reaction barrier,which is attributed to the surface cooperative effect by the surface hydroxyl group that can form a hydrogenbond with the incoming second water molecule. The third water molecule adsorption exhibits a higher reactionbarrier than the first and the second water molecule adsorption channels but yields a thermodynamicallymore stable product. In general, it is expected that the surface Si−Cl bonds can be subjected to the substitutionreactions by water molecules, yielding surface Si−OH bonds, which can be a good initial template forsubsequent surface chemical modifications. However, oversaturations can be a competing side reaction undersevere conditions, suggesting that the precise control of surface kinetic environments is necessary to tailorthe final surface characteristics.
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