In situ investigation of conducting interface formation in LaAlO3/SrTiO3 heterostructure

TL;DR

This study uses in situ spectroscopy to uncover the mechanisms behind the formation of high-mobility conducting interfaces in LaAlO3/SrTiO3 heterostructures, revealing how built-in potential and surface treatments influence interface conductivity.

Contribution

It provides the first in situ analysis of the CI formation mechanism, showing how UV-irradiation and oxygen exposure modulate the built-in potential and interface conductivity.

Findings

Built-in potential proportional to LAO thickness in as-grown samples.

CI appears above 3 unit cells of LAO in as-grown samples.

UV-irradiation removes the built-in potential, enabling CI below 3 UC.

Abstract

The high-mobility conducting interface (CI) between LaAlO_{3}(LAO) and SrTiO_{3}(STO) has revealed many fascinating phenomena, including exotic magnetism and superconductivity. But, the formation mechanism of the CI has not been conclusively explained. Here, using in situ angle-resolved photoemission spectroscopy, we elucidated the mechanisms for the CI formation. In as-grown samples, we observed a built-in potential (V_{bi}) proportional to the polar LAO thickness starting from the first unit cell (UC) with CI formation appearing above 3 UCs. However, we found that the V bi is removed by synchrotron ultraviolet (UV)-irradiation; The built-in potential is recovered by oxygen gas (O_{2}(g))-exposure. Furthermore, after UV-irradiation, the CI appears even below 3UC of LAO. Our results demonstrate not only the V_{bi}-driven CI formation in asgrown LAO/STO, but also a new route to control of the interface state by UV lithographic patterning or other surface modification.