Enhanced superconductivity in SrTiO3 -based interfaces via amorphous Al2O3 capping

Oxide interfaces feature unique two-dimensional (2D) electronic systems with diverse electronic properties such as tunable spin-orbit interaction and superconductivity. Conductivity emerges in these interfaces when the thickness of an epitaxial polar layer surpasses a critical value, leading to charge transfer to the interface. Here, we show that depositing amorphous Al₂O₃ on top of the polar oxide can reduce the critical thickness and enhance the superconducting properties for SrTiO₃-based interfaces. A detailed transmission electron microscopy analysis reveals that the enhancement of the superconducting properties is linked to the expansion of the SrTiO₃ lattice in a direction perpendicular to the interface. We propose that the increase in the superconducting critical temperature, Tc, is a result of epitaxial strain.