The competition between van der Waals and ionic interactions at the SrTiO3/mica heterointerface

Growing a 3D film on a 2D substrate, a process often referred to as quasi-van der Waals (vdW) epitaxy, is generally believed to involve both chemical and vdW interactions at the interface. To date, the competition between chemical and vdW interactions at the interface has yet to be established. In this work, we demonstrate that the chemical activity of deposited species is crucial for determining the structure of the 3D/2D heterointerface. During pulsed laser deposition, the chemical activity of SrTiO3 (STO) can be adjusted by controlling the oxygen partial pressure. Therefore, the relative contributions of chemical and vdW interactions at the STO/mica interface can be tuned. This finding ultimately explains the coexistence of [111] and [001] orientations in STO epitaxy on mica.