Dynamics of Near-Interface Atomic Plane Rearrangement in WO₃/SrTiO₃(001)

Interfaces of complex oxides can exhibit properties not realized in the consitituent materials. The chemistry that occurs at such interfaces has received relatively little attention, yet can be very influential and permit control of interfacial properties, if it is well understood. Here we focus on a dramatic interface chemical effect - the apparent dissolution of an entire atomic plane during WO₃heteroepitaxy on TiO₂-terminated SrTiO₃(001). Transmission electron microscopy indicates that the first subsurface SrO monolayer is completely removed, resulting in the formation of a TiO₂bi-layer at the interface. In combination with x-ray photoelectron spectroscopy measurements, these data suggest that at least a fraction of the Sr from this layer dissolves into the WO₃film. To assist interpretation of the TEM data, we determined the thermodynamic stability of candidate interfacial strucutres using ab initio(density functional theory) simulations and linked these stabilities to the growth conditions. The analysis of near-interface diffusion pathways suggests ways in which SrO dissolution takes place, and how manipulation with the growth conditions can shift the thermodynamic preference from one structure to another.