Relating Energy Level Alignment and Amine-Linked Single Molecule Junction Conductance

• Main Authors: Dell'Angela, M, Kladnik, G, Cossaro, A, Verdini, A, Kamenetska, M, Tamblyn, I, Quek, S. Y, Neaton, J. B, Cvetko, D, Morgante, A, Venkataraman, L
• Format: Journal Article
• Language: English
• Published: 21-06-2010
• Subjects: Physics - Mesoscale and Nanoscale Physics
• DOI: 10.48550/arxiv.1006.4187

Using photoemission spectroscopy, we determine the relationship between
electronic energy level alignment at a metal-molecule interface and
single-molecule junction transport data. We measure the position of the highest
occupied molecular orbital (HOMO) relative to the Au metal Fermi level for
three 1,4-benzenediamine derivatives on Au(111) and Au(110) with ultraviolet
and resonant x-ray photoemission spectroscopy. We compare these results to
scanning tunnelling microscope based break-junction measurements of single
molecule conductance and to first-principles calculations. We find that the
energy difference between the HOMO and Fermi level for the three molecules
adsorbed on Au(111) correlate well with changes in conductance, and agree well
with quasiparticle energies computed from first-principles calculations
incorporating self-energy corrections. On the Au(110) which present Au atoms
with lower-coordination, critical in break-junction conductance measurements,
we see that the HOMO level shifts further from the Fermi level. These results
provide the first direct comparison of spectroscopic energy level alignment
measurements with single molecule junction transport data.