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Rectificación en las uniones de túneles moleculares basadas en alcanetiolados con complejos bipiridina-metal

Junwoo Park¹, Lee Belding¹, Li Yuan¹

¹Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States.

Journal of the American Chemical Society

|January 22, 2021

Resumen

Las uniones de túneles moleculares con cobalto rectifican la corriente debido a los orbitales LUMO accesibles en sesgo positivo. Las uniones de cobre no se rectifican porque los orbitales HOMO y LUMO son accesibles, alterando los mecanismos de transferencia de carga.

Área de la Ciencia:

Ciencias de los materiales
La electrónica molecular
Química

Sus antecedentes:

Las uniones de túnel molecular son cruciales para los dispositivos electrónicos a nanoescala.
Las monocapas autoensambladas de alcanetiolato (SAM) en superficies de oro permiten arquitecturas moleculares controladas.
Los complejos bipiridina-metal ofrecen propiedades electrónicas sintonizables para las uniones moleculares.

Objetivo del estudio:

Investigar el mecanismo de rectificación de corriente en las uniones de túneles moleculares.
Comprender el papel de los iones metálicos (cobalto frente a cobre) en el comportamiento de la unión.
Para correlacionar la estructura electrónica con las propiedades de rectificación observadas.

Principales métodos:

Fabricación de uniones de túneles moleculares utilizando alcaniolatos con grupos de cabeza de bipiridina complejos con CoCl2 o CuCl2.
Caracterización eléctrica de las uniones Au-SAM-EGaIn bajo sesgo variable.
Análisis de la accesibilidad orbital molecular (HOMO/LUMO) en relación con la rectificación.

Principales resultados:

Las uniones Au-S(CH2) 11BIPY-CoCl2 mostraron una rectificación de corriente significativa (r=82,0 a ±1,0 V).
Las uniones Au-S(CH2) 11BIPY-CuCl2 no mostraron ninguna rectificación (r=1,0).
Las uniones de cobalto tenían un LUMO accesible en el sesgo positivo y HOMO / LUMO inaccesible en el sesgo negativo, mientras que las uniones de cobre tenían HOMO y LUMO accesibles en ambos sesgos.

Conclusiones:

La rectificación en las uniones basadas en Co se atribuye a la accesibilidad selectiva del orbital LUMO en sesgo positivo.
La falta de rectificación en las uniones basadas en Cu se debe a los orbitales HOMO y LUMO accesibles tanto en sesgos positivos como negativos.
Las diferencias en los mecanismos de transporte de carga (Fowler-Nordheim frente al túnel directo) en el sesgo negativo explican las diferentes ratios de rectificación.

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