Probing local electric field and conformational switching in single-molecule break junctions

By performing inelastic electron tunneling spectroscopy on single-molecule junctions fabricated through electromigration, we were able to detect polarity-dependent frequency shifts in the molecular vibrational spectra. This observation in conjunction with a simple theoretical model is used to infer the magnitude of local electric field (a crucial and previously inaccessible parameter for understanding charge transport in single-molecule junctions) on the molecule. Electric field induced conformational changes are also detected within this set of measurements.