Chemistry and structure of homoepitaxial SrTiO${}_3$ films and their influence on oxide-heterostructure interfaces

Abstract

The properties of single-crystal SrTiO${}_3$ substrates and homoepitaxial SrTiO${}_3$ films grown by pulsed laser deposition have been compared, in order to understand the loss of interfacial conductivity when more than a critical thickness of nominally homoepitaxial SrTiO${}_3$ is inserted between a LaAlO${}_3$ film and a SrTiO${}_3$ substrate. In particular, the chemical composition and the structure of homoepitaxial SrTiO${}_3$ investigated by low-energy ion-scattering and surface x-ray diffraction, show that for insulating heterointerfaces, a Sr-excess is present between the LaAlO${}_3$ and homoepitaxial SrTiO${}_3$. Furthermore, an increase in the out-of-plane lattice constant is observed in LaAlO${}_3$, indicating that the conductivity both with and without insertion of SrTiO${}_3$ thin film originates from a Zener breakdown associated with the polar catastrophe. When more than a critical thickness of homoepitaxial SrTiO${}_3$ is inserted between LaAlO${}_3$ and SrTiO${}_3$, the electrons transferred by the electronic reconstruction are trapped by the formation of a Sr-rich secondary phase and Sr-vacancies. The migration of Sr towards the surface of homoepitaxial STO and accompanying loss of interfacial conductivity can be delayed by reducing the Sr-content in the PLD target.

Cited by in corpus (2)

• Bandgap Controlling of the Oxygen-Vacancy-Induced Two-Dimensional Electron Gas in SrTiO3
• Sequential pulsed laser deposition of homoepitaxial SrTiO${}_3$ thin films