In situ optical monitoring and effect of initial film temperature on pulsed laser-induced dewetting of ultrathin Ag films

The dewetting conditions of ultrathin Ag films under pulsed laser annealing were investigated. Ag films with a nominal average thickness of 9 nm were deposited on fused silica substrates by DC magnetron sputtering and annealed using a KrF excimer laser (λ = 248 nm and pulse width = 5 ns). The annealing process was monitored in situ via spectrophotometric transmittance measurements over a wavelength range of 230–1000 nm, while the resulting microstructural changes were characterized by atomic force microscopy and scanning electron microscopy imaging. Depending on the laser energy density, the films underwent transitions from smooth surfaces to bi-continuous layers and eventually to well-separated nanoparticles. Experimental results were compared with numerical simulations based on a 1D heat transfer model, simulating the evolution of the film's temperature during each laser pulse. The theoretical minimum laser energy density (40–43 mJ/cm2 at room temperature) required to initiate dewetting aligned closely with experimental observations. This study highlights the influence of initial film temperature, demonstrating that higher temperatures lower the energy density threshold for dewetting and vice versa.