posted on 2023-01-05, 13:03authored byYujing Wei, Liang Li, Julia E. Greenwald, Latha Venkataraman
Understanding
how molecular geometry affects the electronic properties
of single-molecule junctions experimentally has been challenging.
Typically, metal–molecule–metal junctions are measured
using a break-junction method where electrode separation is mechanically
evolving during measurement. Here, to probe the impact of the junction
geometry on conductance, we apply a sinusoidal modulation to the molecular
junction electrode position. Simultaneously, we probe the nonlinearity
of the current–voltage characteristics of each junction through
a modulation in the applied bias at a different frequency. In turn,
we show that junctions formed with molecules that have different molecule–electrode
interfaces exhibit statistically distinguishable Fourier-transformed
conductances. In particular, we find a marked bias dependence for
the modulation of junctions where transmission is mediated thorough
the van der Waals (vdW) interaction. We attribute our findings to
voltage-modulated vdW interactions at the single-molecule level.