With the development of layer-by-layer growth techniques such as molecular beam epitaxy (MBE), it is now possible to construct materials with atomic-level precision, with the layer sequence primarily determined by the growth recipe. However, materials can still restructure in the high-temperature growth environment with surface thermodynamics strongly influencing growth behavior. Here, we demonstrate that growth on SrTiO 3 SrTiO₃ (001), the principal platform for oxide electronics, does not occur in a layer-by-layer fashion but follows a more complex process in which a TiO 2 TiO₂ plane continually diffuses toward the growth surface. Employing in situ synchrotron X-ray scattering combined with ab initio thermodynamic calculations, we discover the existence of a stable TiO 2 TiO₂ double-layer structure on the pristine substrate and the occurrence of dynamic layer rearrangement during homoepitaxial growth by oxide MBE. Our findings suggest that the current methods used to precisely control SrTiO 3 SrTiO₃ surfaces are limited, as well as our ability to dictate the composition of ultrathin films, resulting in important ramifications regarding the surface reactivity of perovskite materials grown on SrTiO 3 SrTiO₃.
Tung et al. (Fri,) studied this question.