Thermocapillary effects in driven dewetting and self assembly of pulsed-laser-irradiated metallic films

Abstract

In this paper the lubrication-type dynamical model is developed of a molten, pulsed-laser-irradiated metallic film. The heat transfer problem that incorporates the absorbed heat from a single beam or interfering beams is solved analytically. Using this temperature field, we derive the three-dimensional long-wave evolution partial differential equation for the film height. To get insights into dynamics of dewetting, we study the two-dimensional (2D) version of the evolution equation by means of a linear stability analysis and by numerical simulations. The stabilizing and destabilizing effects of various system parameters, such as the peak laser beam intensity, the film optical thickness, the reflectivity, and the Biot and Marangoni numbers, are elucidated. It is observed that the film stability is promoted for such parameter variations that increase the heat production in the film. In the numerical simulations the impacts of different irradiation modes are investigated. In particular, we obtain that in the interference heating mode the spatially periodic irradiation results in a spatially periodic film rupture with the same or nearly equal period. The 2D model qualitatively reproduces the results of the experimental observations of a film stability and spatial ordering of a resolidified nanostructures.