Optical micrographs of one-dimensional (1D) and 2D gratings created on a gold film of thickness. The structures were obtained with a single, pulse at , of two-beam and four-beam interferences with peak intensities (a) and (b) .
AFM images of Au film after two-beam interference irradiation and schematic intensity profiles (above the images). (a) Peak intensity , ten pulses. Beading of the film at “hot” regions and motion of the beads towards the “cold” regions are clearly seen. (b) , ten pulses. Hot regions become empty of all film material, which has moved to the cold regions.
AFM images of Au film after four-beam interference irradiation showing beading of the film at the hot spot where the film was molten (a) and how the hot spot empties of all film material, as all beads move to the cold periphery (b). Peak intensities (a) and (b) one pulse.
AFM images of Au film after two-beam (a) and four-beam interference irradiations (b). Peak intensities in both cases. High and narrow ridges are formed due to the hydrodynamic flow of liquid film from hot to cold regions. [(c) and (d)] Appropriate section profiles.
Intensity threshold measured as a function of film thickness . The curves are the results of calculation for various periodicities: (1) ; (2) ; (3) ; and (4) . The experimental points were obtained for a periodicity .
Distance between adjacent ridges depends on the peak intensity. At a particular intensity ( for ; single pulse case shown in the figure) the ridges moving in opposite directions coalesce.
AFM image (a) and section analysis (b) of the film after two-beam interference irradiation with a single pulse at high intensity . Fast ablation of the hot regions prevents hydrodynamic flow of the liquid Au layer. The film is left on the substrate only in the cold regions. The thickness of the remaining film is the same as before irradiation.
Calculated (solid line) and measured dependencies of the reflectivity as a function of the film thickness. The calculations are based on Eq. (6) with , , and .
Calculated temperature profiles at for various times during irradiation (4 and ) and after irradiation (10 and ) of Au film with peak intensity of and periods of (a), (b), and (c). (1) ; (2) ; (3) ; and (4) .
Distance between the linear ridges (a) and the diameter of holes (b) as functions of the peak intensity in comparison with the calculated values. ; (a) and (b) .
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