Tailoring film agglomeration for preparation of silver nanoparticles with controlled morphology

Abstract

Thin metal films can disintegrate into nanoparticles upon thermal annealing. In this work, to obtain silver nanoparticles with controlled morphology, we performed a comparison study on the surface topography evolutions and agglomeration mechanisms of Ag films deposited by magnetron sputtering within-situ annealing (the heating rate is 0.33°C/s) and ex-situ rapid thermal annealing (the heating rate is 100°C/s) treatments, respectively. The results confirm that the in-situ annealed Ag films agglomerate via voids nucleation followed by the fractal growth of voids. Moreover, we found that the critical void radius upon which the void growth is favored decreases with increasing the annealing temperature. For the case of rapid annealing, the agglomeration of Ag films follows the grain boundary grooving mechanism due to the rather higher heating rate. Compared with the in-situ heating process, the rapid annealing treatment allows a more uniform size distribution of the nanoparticles. Our findings highlight the key role of heating rate on the size, shape and functionalities of Ag nanoparticles for a wide range of practical applications, and enrich the understandings of the agglomeration mechanism of thin metal films.