Water adsorption on hydrogen-passivated silicon nanowires from density functional theory with dispersion correction

Density functional theory with semiempirical dispersion correction has been applied to investigate water monomer adsorption onto the surface of hydrogen-passivated silicon nanowires (h-SiNWs) of different shapes and growth orientations. We find that water adsorption is in the weak physisorption limit, leading to a hydrophobic surface. The adsorption site and orientation are determined by electrostatic interactions involving both the surface and interior atoms of the h-SiNWs and are not affected qualitatively by including the dispersion correction. The barrier for water diffusing on the surface of h-SiNWs depends sensitively on the nanowire facet and growth orientation. The barrier for water rotation is small, which may facilitate water cluster formation on the h-SiNWs.