Interfacial Sr diffusion stabilized (Ca,Sr)TaO3 thin film and its semiconducting behaviors

Perovskite-structured materials host enormous phases such as superconductivity, ferromagnetism, and ferroelectricity, which largely rely on the states of transition metal octahedra. Compared to the extensively studied 3d-orbital perovskite, heavier elements (such as Ta, W, and Ir) with 5d orbitals are of great interest due to their stronger spin–orbital coupling related physics. However, due to the difficulty in synthesis, research on 5d-element perovskite is quite limited. Here, we synthesized tantalate perovskite (Ca,Sr)TaO3 films by pulsed laser deposition. Structural characterizations indicate that the films are epitaxial to the substrates. By tuning the growth parameters such as oxygen partial pressure and growth temperatures, the carrier density can be tuned from ∼1014 to ∼1016 cm−2 while maintaining semiconducting behavior. We found that the interfacial Sr diffusion from the substrate to the film is critical for its structural stabilization. Analogous to KTaO3, our synthesis of (Ca,Sr)TaO3 perovskite films offers a new platform for the study of interfacial physics.