title: Measurement of the electron-phonon coupling factor dependence on film thickness and grain size in Au, Cr, and Al.
abstract: Femtosecond thermoreflectance data for thin films and bulk quantities of Au, Cr, and Al are compared with the parabolic two-step thermal diffusion model for the purpose of determining the electron-phonon coupling factor. The thin films were evaporated and sputtered onto different substrates to produce films that vary structurally. The measurement of the electron-phonon coupling factor is shown to be sensitive to grain size and film thickness. The thin-film thermoreflectance data are compared with that of the corresponding bulk material and to a theoretical model relating the coupling rate to the grain-boundary scattering and size effects on the mean free path of the relevant energy carrier.
authors.affiliation: Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, Virginia 22903, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Hostetler
authors.forename: A N
authors.initials: AN
authors.lastname: Smith
authors.forename: D M
authors.initials: DM
authors.lastname: Czajkowsky
authors.forename: P M
authors.initials: PM
authors.lastname: Norris