Fabrication of oxide/FeSe multilayer films using pulsed laser deposition

In this study, we demonstrate the successful fabrication of TiO₂/FeSe/SrTiO₃ and TiO₂/FeSe/LaAlO₃ heterostructures using PLD. When the growth rates were sufficiently low, anatase TiO₂, which has been reported to induce superconductivity in FeSe, could be grown epitaxially on FeSe. For TiO₂/FeSe/SrTiO₃ with FeSe layers thicker than 5 nm, the FeSe/TiO₂ interface was clean, as confirmed by the observation of Laue fringes around the FeSe(001) reflection. Although a thinner FeSe layer is expected to enhance Tc, we could not observe such behavior because it was difficult to realize interfacial superconductivity while growing anatase TiO₂. Most strikingly, superconductivity appeared when TiO₂ was deposited on FeSe/LaAlO₃, clearly demonstrating that the interaction between the top oxide layer and underlying FeSe can induce superconductivity. This work demonstrates the feasibility of fabricating FeSe/oxide superlattices by PLD, establishing a platform for the exploration of interfacial superconductivity in iron-based superconductors.