Linking electronic transport through a spin crossover thin film to the molecular spin state using X-ray absorption spectroscopy operando techniques

TL;DR

This study demonstrates a direct correlation between the molecular spin state and electronic transport in a spin crossover thin film using operando X-ray absorption spectroscopy, advancing understanding of molecular device behavior.

Contribution

It introduces a dual operando methodology linking molecular spin states to charge transport in solid-state devices, providing new insights into spin crossover device mechanisms.

Findings

Transport involves a subset of molecules within the film.

A correlation exists between resistance and Fe spin state.

Fe molecular site mediates charge transport.

Abstract

One promising route toward encoding information is to utilize the two stable electronic states of a spin crossover molecule. However, while this property is clearly manifested in transport across single molecule junctions, evidence linking charge transport across a solid-state device to the molecular film's spin state has thus far remained indirect. To establish this link, we deploy materials-centric and device-centric operando experiments involving X-ray absorption spectroscopy. We find a correlation between the temperature dependencies of the junction resistance and the Fe spin state within the device's Fe(bpz)2(phen) molecular film. We also factually observe that the Fe molecular site mediates charge transport. Our dual operando studies reveal that transport involves a subset of molecules within an electronically heterogeneous spin crossover film. Our work confers an insight that substantially improves the state-of-the-art regarding spin crossover-based devices, thanks to a methodology that can benefit device studies of other next-generation molecular compounds.