Li@C60 as a multi-state molecular switch

Henry J Chandler,Eleanor E B Campbell,Renald Schaub,Minas Stefanou

doi:10.1038/s41467-019-10300-2

Abstract

The field of molecular electronics aims at advancing the miniaturization of electronic devices, by exploiting single molecules to perform the function of individual components. A molecular switch is defined as a molecule that displays stability in two or more states (e.g. “on” and “off” involving conductance, conformation etc.) and upon application of a controlled external perturbation, electric or otherwise, undergoes a reversible change such that the molecule is altered. Previous work has shown multi-state molecular switches with up to four and six distinct states. Using low temperature scanning tunnelling microscopy and spectroscopy, we report on a multi-state single molecule switch using the endohedral fullerene Li@C60 that displays 14 molecular states which can be statistically accessed. We suggest a switching mechanism that relies on resonant tunnelling via the superatom molecular orbitals (SAMOs) of the fullerene cage as a means of Li activation, thereby bypassing the typical vibronic excitation of the carbon cage that is known to cause molecular decomposition.

Highlights

The field of molecular electronics aims at advancing the miniaturization of electronic devices, by exploiting single molecules to perform the function of individual components
Molecular switches with multiple states, like that observed by Auwärter et al match these criteria[6]
With all measurements being performed near liquid-helium temperatures, we rule out migration of the Li within the cage[16] unless purposefully induced by our STM experiments

Summary

Introduction

The field of molecular electronics aims at advancing the miniaturization of electronic devices, by exploiting single molecules to perform the function of individual components. Using low temperature scanning tunnelling microscopy and spectroscopy, we report on a multi-state single molecule switch using the endohedral fullerene Li@C60 that displays 14 molecular states which can be statistically accessed. A single magnetic atom was recently demonstrated to act as a reliable memory bit, capable of being toggled between two magnetic states[13]. This represents the ultimate miniaturisation of an electronic component. As first predicted 25 years ago[32], the prototypical endofullerene Li@C60 could potentially reveal multi-state switching capabilities by exploiting the relocation of the off-centred Li atom within the carbon cage. Careful analysis of variations in the superatom molecular orbital energies (SAMO33,34) allows the potential energy landscape inside an endofullerene to be explored

Methods

Results

Conclusion