Electronic Reconstruction Enhanced Tunneling Conductance at Terrace Edges of Ultrathin Oxide Films

TL;DR

This study reveals that atomic-scale terrace edges in ultrathin BaTiO3 films cause local electronic reconstruction, significantly enhancing tunneling conductance, which can be controlled and utilized in oxide electronic devices.

Contribution

It demonstrates that terrace edges induce electronic reconstruction that enhances tunneling conductance in ultrathin oxide films, a phenomenon previously not well understood.

Findings

Enhanced tunneling conductance near terrace edges observed.

Electronic reconstruction reduces local tunneling barrier width.

Conductance enhancement can be controlled via surface termination engineering.

Abstract

Quantum mechanical tunneling of electrons across ultrathin insulating oxide barriers has been studied extensively for decades due to its great potential in electronic device applications. In the few-nanometer-thick epitaxial oxide films, atomic-scale structural imperfections, such as the ubiquitously existed one-unit-cell-high terrace edges, can dramatically affect the tunneling probability and device performance. However, the underlying physics has not been investigated adequately. Here, taking ultrathin BaTiO3 films as a model system, we report an intrinsic tunneling conductance enhancement near the terrace edges. Scanning probe microscopy results demonstrate the existence of highly-conductive regions (tens of nanometers-wide) near the terrace edges. First-principles calculations suggest that the terrace edge geometry can trigger an electronic reconstruction, which reduces the effective tunneling barrier width locally. Furthermore, such tunneling conductance enhancement can be discovered in other transition-metal-oxides and controlled by surface termination engineering. The controllable electronic reconstruction could facilitate the implementation of oxide electronic devices and discovery of exotic low-dimensional quantum phases.