Indirect heating of Pt by short-pulse laser irradiation of Au in a nanoscale Pt/Au bilayer

Abstract

Thermal transport in a metallic multilayer on picosecond time scales is controlled by the electronic thermal conductivity ( e), the electronic interfacial thermal conductance (Gee), and electron-phonon coupling constant (g). We analyze heat transfer in a nanoscale Pt/Au bilayer using data obtained in pump-probe measurements and modeling using a transmission-line-equivalent circuit. For optical exciation of either the Pt or Au side of the bilayer, the majority of energy is deposited into the Pt phonons on a time scale of 1 ps because gPt gAu and Gee > gAuhAu, where hAu is the thickness of the Au layer. We determine g of the Au layer and set a lower bound on Gee of the Pt/Au interface: gAu = 2.2 ± 0.6 × 1016 W m−3 K−1 and Gee > 5 GW m−2 K−1.