Anisotropic transport at the LaAlO3/SrTiO3 interface explained by microscopic imaging of channel-flow over SrTiO3 domains

TL;DR

This study uses microscopic imaging to reveal how SrTiO3 structural domains influence anisotropic transport in LaAlO3/SrTiO3 interfaces, showing domain configurations can significantly modulate current flow and device behavior.

Contribution

It provides a detailed microscopic understanding of how SrTiO3 domains affect macroscopic transport anisotropy in LaAlO3/SrTiO3 interfaces, linking local current paths to global device properties.

Findings

Up to 95% of current can be modulated by domains.

Domain configurations change with cooldowns and electric fields.

Structural domains divert current flow, causing anisotropic resistance.

Abstract

Oxide interfaces, including the LaAlO3/SrTiO3 interface, have been a subject of intense interest for over a decade due to their rich physics and potential as low dimensional nanoelectronic systems. The field has reached the stage where efforts are invested in developing devices. It is critical now to understand the functionalities and limitations of such devices. Recent scanning probe measurements of the LaAlO3/SrTiO3 interface have revealed locally enhanced current flow and accumulation of charge along channels related to SrTiO3 structural domains. These observations raised a key question regarding the role these modulations play in the macroscopic properties of devices. Here we show that the microscopic picture, mapped by scanning superconducting quantum interference device, accounts for a substantial part of the macroscopically measured transport anisotropy. We compared local flux data with transport values, measured simultaneously, over various SrTiO3 domain configurations. We show a clear relation between maps of local current density over specific domain configurations and the measured anisotropy for the same device. The domains divert the direction of current flow, resulting in a direction dependent resistance. We also show that the modulation can be significant and that in some cases up to 95% of the current is modulated over the channels. The orientation and distribution of the SrTiO3 structural domains change between different cooldowns of the same device or when electric fields are applied, affecting the device behavior. Our results, highlight the importance of substrate physics, and in particular, the role of structural domains, in controlling electronic properties of LaAlO3/SrTiO3 devices. Further, these results point to new research directions, exploiting the STO domains ability to divert or even carry current.