Effect of near-field optical angular momentum on molecular junctions

Abstract

The role of molecular junctions in nanoelectronics is most often associated with electronic transport; however, their precise characterisation hinders their widespread development. The interaction of light with molecular junctions is a supplementary factor for the development of molecular switches, but it has rarely been addressed. The influence of light interaction with molecular junctions on the response of molecules in the near field was demonstrated by properly characterising the optical angular momentum at the junctions. Consequently, the molecular switching dynamics were observed in the Raman signatures of the conducting molecules. The illumination geometry and voltage applied to the junction were changed to demonstrate numerically and experimentally how the Raman intensity can be turned ON and OFF with a difference of nearly five orders of magnitude. These molecular-scale operations result from the combined interaction of a current-induced electronic rearrangement in the molecular junction and a plasmonically enhanced electromagnetic field near the tip of the junction. This study of the effect of optical angular momentum on the near field of the molecular junction shows significant potential for the development of molecular electronics.

Keywords

• molecular junctions
• near-field enhancement
• raman spectroscopy
• localised angular momentum