Dewetting of Au/Ni bilayer films on prepatterned substrates and the formation of arrays of supersaturated Au-Ni nanoparticles

Abstract

Au/Ni bilayer thin films are studied with respect to their dewetting behavior on prepatterned SiO2/Si substrates (inverted pyramidal pits). Dewetting of Au-Ni solid-solutions is controlled by a rapid thermal treatment at temperatures above the miscibility gap followed by a fast cooling procedure. Upon annealing, it is observed that some Au-rich film material separates on the mesa in case of still coalescent (i.e., incomplete dewetting) nanoparticles. Moreover, arrays of supersaturated Au-Ni solid-solution nanoparticles are formed out of the bilayer film after templated dewetting. Faceting of the nanoparticles indicates textural effects. In order to prove that these findings are caused by the prepatterned substrate, a comparison with the bilayer dewetting on a flat SiO2/Si substrate is provided.