posted on 2021-09-16, 19:07authored bySongsong Li, Hao Yu, Jialing Li, Nicholas Angello, Edward R. Jira, Bo Li, Martin D. Burke, Jeffrey S. Moore, Charles M. Schroeder
Efficient long-range charge transport
is required for high-performance
molecular electronic devices. Resonant transport is thought to occur
in single molecule junctions when molecular frontier orbital energy
levels align with electrode Fermi levels, thereby enabling efficient
transport without molecular or environmental relaxation. Despite recent
progress, we lack a systematic understanding of the transition between
nonresonant and resonant transport for molecular junctions with different
chemical compositions. In this work, we show that molecular junctions
undergo a reversible transition from nonresonant tunneling to resonant
transport as a function of applied bias. Transient bias-switching
experiments show that the nonresonant to resonant transition is reversible
with the applied bias. We determine a general quantitative relationship
that describes the transition voltage as a function of the molecular
frontier orbital energies and electrode Fermi levels. Overall, this
work highlights the importance of frontier orbital energy alignment
in achieving efficient charge transport in molecular devices.