Effect of strain, thickness, and local surface environment on electron transport properties of oxygen-terminated copper thin films

TL;DR

This study investigates how strain, thickness, and surface environment affect electron transport in oxidized copper thin films using density functional theory, revealing surface transmission limitations and strain effects on conductance.

Contribution

It provides new insights into electron transport in oxidized copper films, highlighting the impact of surface oxidation, film thickness, and strain on transmission properties.

Findings

Surface oxidation leads to universally low electron transmission.

Thicker films (>2.7 nm) show similar transmission behavior with depth.

Tensile strain reduces electron transmission compared to unstrained films.

Abstract

Electron transport is studied in surface oxidized single-crystal copper thin films with a thickness of up to 5.6 nm by applying density functional theory and density functional tight binding methods to determine electron transport properties within the ballistic regime. The variation of the electron transmission as a function of film thickness as well as the different contributions to the overall electron transmission as a function of depth into the the films is examined. Transmission at the oxidized copper film surfaces is found to be universally low. Films with thickness greater than 2.7 nm exhibit a similar behavior in local transmission per unit area with depth from the film surface; transmission per unit area initially increases rapidly and then plateaus at a depth of approximately 0.35-0.5 nm away from the surface, dependent on surface facet. Unstrained films tend to exhibit a higher transmission per unit area than corresponding films under tensile strain.