Evolution of self-assembled Ag nanostructures on c-plane sapphire by the systematic control of annealing temperature

The morphological evolution of various Ag nanostructures on c-plane sapphire is systematically investigated through the solid-state-dewetting by the control of annealing temperature between 200 and 950 °C with the Ag films of 60 and 10 nm. Various configurations of Ag nanostructures including Ag voids, wiggly and round nanoparticles are fabricated with the 60 nm due to the annealing temperature dependent surface diffusion, surface energy minimization and Ag sublimation. As a sharp distinction, highly dense semi-spherical nanoparticles are fabricated with the 10 nm set throughout the temperature range due to a much higher dewetting degree induced by the enhanced surface diffusion with a much thinner film. The reflectance spectra shows a spectral shift along with the size variation, i.e. blue shift with the decreased size and vice versa. The reflectance and Raman spectra reveal a sharp distinction between the two sets along with the strong correlation to the nanostructure morphology.