Electric
Field Breakdown in Single Molecule Junctions
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Abstract
Here
we study the stability and rupture of molecular junctions
under high voltage bias at the single molecule/single bond level using
the scanning tunneling microscope-based break-junction technique.
We synthesize carbon-, silicon-, and germanium-based molecular wires
terminated by aurophilic linker groups and study how the molecular
backbone and linker group affect the probability of voltage-induced
junction rupture. First, we find that junctions formed with covalent
S–Au bonds are robust under high voltage and their rupture
does not demonstrate bias dependence within our bias range. In contrast,
junctions formed through donor–acceptor bonds rupture more
frequently, and their rupture probability demonstrates a strong bias
dependence. Moreover, we find that the junction rupture probability
increases significantly above ∼1 V in junctions formed from
methylthiol-terminated disilanes and digermanes, indicating a voltage-induced
rupture of individual Si–Si and Ge–Ge bonds. Finally,
we compare the rupture probabilities of the thiol-terminated silane
derivatives containing Si–Si, Si–C, and Si–O
bonds and find that Si–C backbones have higher probabilities
of sustaining the highest voltage. These results establish a new method
for studying electric field breakdown phenomena at the single molecule
level