Strain Effect on the Dissociation of Water Molecules on Silicene: Density Functional Theory Study

Dissociative adsorption of water molecules on silicene is an efficient way to open the band gap of silicene for electronic applications. However, the dissociation of H2O molecules on silicene is difficult due to the Pauli exclusion effect between H2O molecules and silicene. By using density functional theory calculations, we investigated the effect of strain on the dissociative barrier of H2O molecules on silicene. Our results demonstrate that the tensile strain can significantly reduce the dissociative energy barrier of H2O molecules on silicene, whereas the compressive strain has slight effect on the dissociation barrier. In addition, the dissociation barrier reduces from 0.85 to 0.27 eV with the tensile strain of 9%, where the reaction time for the dissociation of H2O on silicene can be reduced significantly from 2.23 x 10(2) to 3.60 x 10(-8) s. The mechanism for the effect of strains on the depressed dissociation barrier of H2O molecules on silicene can be understood through analyzing the density of states and orbital charge of the water/silicene system. The band gap of silicene is 0.37 eV after the dissociation of H2O molecules, and the carrier mobility is relatively high, which is important for its applications in logic circuits. Further study indicates that the dissociation of H2O is favorite at atomic vacancy and grain boundary of silicene with and without strain.