Atomistic Mechanics and Formation Mechanism of Metal-Molecule-Metal Junctions

The present Letter reports a quantitative analysis of contact mechanics in metal-molecule-metal junctions at a single atom/molecule level
through investigating their lifetime at cryogenic temperature. We elucidated that the force breaking mechanism of atomic/molecular junctions
is stretching speed dependent, attributed to suppression of contact structure relaxation processes at high strain rate conditions. We also
provide solid evidence that strain exerted in the preformation stage of molecular junctions poses extra strain energy that accelerates their
eventual fracture. Nonetheless, we find that single-molecule junctions subjected to mechanical stretching at 0.6 pm/s can be held for ∼100
s on average at 77 K and for a much prolonged period when freezing the elongation after forming the molecular junctions by virtue of
moderate thermal destabilizations, the fluctuation-free condition of which provides optimal experimental platform for performing reliable
measurements of single molecule electron transport properties.