title: Vibrational and electronic heating in nanoscale junctions.
abstract: Understanding and controlling the flow of heat is a major challenge in nanoelectronics. When a junction is driven out of equilibrium by light or the flow of electric charge, the vibrational and electronic degrees of freedom are, in general, no longer described by a single temperature. Moreover, characterizing the steady-state vibrational and electronic distributions in situ is extremely challenging. Here, we show that surface-enhanced Raman emission may be used to determine the effective temperatures for both the vibrational modes and the electrons in the current in a biased metallic nanoscale junction decorated with molecules. Molecular vibrations show mode-specific pumping by both optical excitation and d.c. current, with effective temperatures exceeding several hundred kelvin. Anti-Stokes electronic Raman emission indicates that the effective electronic temperature at bias voltages of a few hundred millivolts can reach values up to three times the values measured when there is no current. The precise effective temperatures are model-dependent, but the trends as a function of bias conditions are robust, and allow direct comparisons with theories of nanoscale heating.
authors.affiliation: Department of Physics and Astronomy, Rice University, 6100 Main Street, Houston, Texas 77005, USA.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Ward
authors.forename: David A
authors.initials: DA
authors.lastname: Corley
authors.forename: James M
authors.initials: JM
authors.lastname: Tour
authors.forename: Douglas
authors.initials: D
authors.lastname: Natelson
mesh_terms: D004581:Electronics; D004583:Electrons; D006358:Hot Temperature; D049329:Nanostructures; D036103:Nanotechnology; D013059:Spectrum Analysis, Raman; D014732:Vibration