An atomic-level study of material ablation and spallation in ultrafast laser processing of gold films

Ablation and spallation of gold thin films by an ultrashort laser pulse are simulated by using an integrated two-temperature model and molecular dynamics method with inclusion of the hot electron blast force. The simulation results show that the ultrafast laser-induced nonthermal ablation and spallation both are essentially due to dynamic tensile stress that exceeds the local material strength. It is also demonstrated that a simultaneous use of femtosecond and picosecond laser pulses could induce spallation without causing undesired front-side damage to the film. This may be suited to peel an ultrathin film (1 mu m in thickness or less) from its substrate or to improve the material removal rate of precise laser processing. (C) 2010 American Institute of Physics. [doi:10.1063/1.3504192]