Reducing surface depletion of superconducting SrTiO_3 films with EuTiO_3 capping layers

摘要

Doped SrTiO_3 thin films are of significant scientific interest for their superconducting, ferroelectric, and thermoelectric properties. Air-exposed thin films of doped SrTiO_3 suffer from surface carrier depletion that makes it difficult to obtain thin, conducting films, especially at low doping densities and temperatures. Here, we show that thin (10 nm) EuTiO_3 capping layers can prevent surface depletion and allow for conducting heterostructures with SrTiO_3 films as thin as 10 nm. We also investigate the superconducting properties of EuTiO_3 capped SrTiO_3 films. We show that the superconducting transition temperature decreases systematically as the SrTiO_3 film thickness is reduced, which is likely due to proximity effects.