Laser-induced dewetting nanomorphologies in single and bilayer metal films

Spatially ordered patterns result under ns laser-induced dewetting of nanoscopic metallic films like Co and Ag on inert substrates like SiO ₂. In both cases, the observed ordering length scale is due to thin film hydrodynamic instability with spinodal-like character. However, the morphological pathway during dewetting is different for the two metals: occurring through development of bicontinuous structures in the case of Ag and by progression of cellular networks for Co. Dewetting in bilayer structures of Ag and Co on SiO₂ show that the morphology evolution is dictated by the thicker of the two films in the bilayer structure. We applied linear stability analysis to predict the length scales in single and bilayer metal film. The experimental observations are in good agreement with theoretical predictions from the analysis. An important result was that the length scales for the bilayer film were significantly smaller than a single layer of the same thickness suggesting that further control of patterning length scales may be achieved through multilayer dewetting.