Control of defect-mediated tunneling barrier heights in ultrathin MgO films

TL;DR

This study investigates how controlling oxygen vacancies in ultrathin MgO films affects tunneling properties, showing that oxygen defect management improves local tunneling behavior and reduces hotspots.

Contribution

It demonstrates that adjusting oxygen defect populations during MgO growth enhances tunneling characteristics by reducing defect-related hotspots.

Findings

Lower density of current hotspots in MgO films

Reduced tunnel current amplitude with oxygen defect control

Defect-based potential landscape influences tunneling behavior

Abstract

The impact of oxygen vacancies on local tunneling properties across rf-sputtered MgO thin films was investigated by optical absorption spectroscopy and conducting atomic force microscopy. Adding O$_2$ to the Ar plasma during MgO growth alters the oxygen defect populations, leading to improved local tunneling characteristics such as a lower density of current hotspots and a lower tunnel current amplitude. We discuss a defect-based potential landscape across ultrathin MgO barriers.