Determining level alignment and coupling strength in single-molecule junctions with chemically-enhanced Raman spectroscopy

Raman spectroscopy can be used at the nanoscale to probe binding geometries [1], molecule concentrations [2], carrier densities [3], and charging effects [4]. In this talk, we use finite-difference total-energy and self-energy corrected density functional theory calculations in conjunction with Landauer framework, to study the Raman spectra and transport properties of model nanoscale interfaces, single-molecule junctions -- individual molecules contacted with macroscopic metallic electrodes. In the cases of 4,4' bipyridine/Gold and polyphenylene venylene/Gold junctions, we will show how conductance and chemically-enhanced Raman measurement can be used in conjunction to determine the energy scales controlling electron transport i.e. frontier orbital energies and coupling strength. \\[4pt] [1] Zayak et al, Phys. Rev. Lett. 106, 083003 (2011)\\[0pt] [2] Zayak et al., J. Phys. Chem Lett. 3 (10), 1357-1362 (2012)\\[0pt] [3] Das et al. Nanotechnology , 3, 210– 215 (2008)\\[0pt] [4] Li et al., PNAS, 111 (4) 1282-1287 (2014)