Electronically coupled complementary interfaces between perovskite band insulators

TL;DR

This study demonstrates the fabrication of electronically coupled LaAlO3/SrTiO3 interfaces with controlled spacing, revealing critical separation distances affecting conductivity while maintaining high carrier mobility, advancing oxide electronic device design.

Contribution

It reports the first realization of coupled complementary oxide interfaces with atomic-scale control, elucidating the effects of interface spacing on electronic properties.

Findings

Critical separation distance of 6 perovskite layers affects conductivity.

High carrier mobility is preserved at sub-nanometer interface spacing.

Decreased carrier density occurs below the critical separation.

Abstract

Perovskite oxides exhibit a plethora of exceptional electronic properties, providing the basis for novel concepts of oxide-electronic devices. The interest in these materials is even extended by the remarkable characteristics of their interfaces. Studies on single epitaxial connections between the two wide-bandgap insulators LaAlO3 and SrTiO3 have revealed them to be either high-mobility electron conductors or insulating, depending on the atomic stacking sequences. In the latter case they are conceivably positively charged. For device applications, as well as for basic understanding of the interface conduction mechanism, it is important to investigate the electronic coupling of closely-spaced complementary interfaces. Here we report the successful realization of such electronically coupled complementary interfaces in SrTiO3 - LaAlO3 thin film multilayer structures, in which the atomic stacking sequence at the interfaces was confirmed by quantitative transmission electron microscopy. We found a critical separation distance of 6 perovskite unit cell layers, corresponding to approximately 2.3 nm, below which a decrease of the interface conductivity and carrier density occurs. Interestingly, the high carrier mobilities characterizing the separate electron doped interfaces are found to be maintained in coupled structures down to sub-nanometer interface spacing.