First principles simulations of electrified silicon/water interfaces

Si-based materials have been used in a myriad of devices, including light-activated systems such as cathodes in photoelectrochemical cells and p-i-n junctions in optoelectronic biomodulators. In both cases, Si surfaces are in contact with water, and the interface is under bias (e.g. under the effect of an electric field). Here we report a study of electrified Si/water interfaces aimed at understanding charge transfer mechanisms between the solid and the liquid, and their influence in determining the performance of optoelectronic devices. In particular, we carried out ab-initio molecular dynamics simulations of the hydrogenated Si(100)/water interface using the Qbox code (http://qboxcode.org), and we investigated the effect of an applied electric field on the band offsets at the interface. We compared our results with patch clamp measurements and we further investigated the modification of the structural properties of water at the interface, induced by an applied bias.