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

Thermal transport in a metallic multilayer on picosecond time scales is controlled by the electronic thermal conductivity (Λₑ), 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 gPtgAu 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.