Liquid motion in laser pulsed Al, Co and Au films

The dynamics of melts with temperatures up to twice the melting temperature and thermal gradients of 109 K/m, as produced by nanosecond laser pulses in `realʹ Al and Au films, were visualized by time-resolved electron microscopy. The melts were destabilized by (1) recoil from evaporating impurity molecules within 10 ns; (2) thermocapillary flow, driving the liquid within 100 ns up or down the laser imposed thermal gradient, depending on the pre-treatment; (3) thermocapillary oscillations with build-up times ≤50 ns and frequencies 5–10 MHz. The flow effects in metal films with native impurities cannot be predicted with surface relevant parameters of the pure material.