# Spatially-resolved, substrate-induced rectification in C$_{60}$ bilayers on copper

## TL;DR

This study shows that uck bilayers on copper exhibit high rectification ratios due to substrate-induced effects, with strong coupling causing metallization of the bottom layer and spatially-dependent electrical behavior, highlighting potential for molecular electronics.

## Contribution

It reveals substrate-induced rectification in uck bilayers on copper, combining experimental and theoretical insights into the electronic structure and transport mechanisms involved.

## Key findings

- Rectification ratios exceeding 1000 at 1.3 V bias.
- Metallization of the bottom uck layer due to strong substrate coupling.
- Spatial dependence of the onset voltage related to intra-layer coordination.

## Abstract

We demonstrate rectification ratios ($RR$) of $\gtrsim$1000 at biases of 1.3~V in bilayers of \buck deposited on copper. Using scanning tunneling spectroscopy and first-principles calculations, we show that the strong coupling between \buck and the Cu(111) surface leads to the metallization of the bottom \buck layer, while the molecular orbitals of the top \buck are essentially unaffected. Due to this substrate-induced symmetry breaking and to a tunneling transport mechanism, the system behaves as a hole-blocking layer, with a spatial dependence of the onset voltage on intra-layer coordination. Together with previous observations of strong electron-blocking character of pentacene/\buck bilayers on Cu(111), this work further demonstrates the potential of strongly-hybridized, \buck-coated electrodes to harness the electrical functionality of molecular components.