Semiconducting behaviors at epitaxial Ca0.5TaO3 interfaces

TL;DR

This study investigates the semiconducting behaviors at epitaxial Ca0.5TaO3 interfaces, revealing how oxygen vacancies and atomic intermixing influence electronic transport, distinct from KTaO3 systems, with implications for interface engineering.

Contribution

It provides new insights into the semiconducting properties of Ca0.5TaO3 interfaces and highlights the role of oxygen vacancies and atomic intermixing in electronic transport.

Findings

Ca0.5TaO3 films show semiconducting behavior with LaAlO3 capping.

Carrier density can be tuned from ~10^14 to 10^16 cm^-2 by growth conditions.

Interfacial atomic intermixing affects electronic transport in tantalite interfaces.

Abstract

Emergent phenomena take place in symmetry-breaking systems, notably the recently discovered two-dimensional electron gas and its tunable superconductivities near the KTaO3 interfaces. Here, we synthesized perovskite Ca0.5TaO3 films along both [001] and [111] orientations. Different from the KTaO3 system, Ca0.5TaO3 films show semiconducting behaviors when capped with LaAlO3 films in both [001] and [111] orientations. By growing films at higher temperatures, more oxygen vacancies can be introduced, and the carrier density can be tuned from ~ 1014 cm-2 to ~ 1016 cm-2. Another difference is that the superconducting transition temperature Tc in KTaO3 (111) increases linearly along with its carrier density, while the Ca0.5TaO3 (111) remains semiconducting when carrier density ranges from ~ 1014 cm-2 to ~ 1016 cm-2. Based on the density function theory calculation, Ca0.5TaO3 and KTaO3 show similar electronic band structures. According to the energy-dispersive X-ray spectroscopy, we found heavy Sr diffusion from the substrate to the Ca0.5TaO3 layer, which may destroy the interfacial conductivity. Our work demonstrates that besides the oxygen vacancies, electronic transport is sensitive to the atomic intermixing near the interface in tantulates.