An Interfacial Tracking Method for Ultrashort Pulse Laser Melting and Resolidification of a Thin Metal Film

An interfacial tracking method is developed to model rapid melting and resolidification of a free-standing metal film subject to an ultrashort laser pulse. The laser energy is deposited to the electrons near thin film surface, and subsequently diffused into deeper part of the electron gas and transferred to the lattice. The energy equations for the electron and lattice are coupled through an electron-lattice coupling factor. Melting and resolidification are modeled by considering the interfacial energy balance and nucleation dynamics. An iterative solution procedure is employed to determine the elevated melting temperature and depressed solidification temperature in the ultrafast phase-change process. The predicted surface lattice temperature, interfacial location, interfacial temperature, and interfacial velocity are compared with those obtained by an explicit enthalpy model. The effects of the electron thermal conductivity models, ballistic range, and laser fluence on the melting and resolidification are also investigated.