Formation of ultrafine uniform gold nanoparticles by sputtering and redeposition

Uniformly distributed Au nanoparticles with controllable size were fabricated by focused ion beam bombardment of thin gold films. In situ scanning electron microscopy and ex situ transmission electron microscopy were used to characterize the nanoparticles. Results show that a dual particle size distribution was generated at low ion fluence, while highly uniform Au particles with diameters around 2 nm formed at high fluence. The balance between sputtering and redeposition is responsible for the formation and size control of the nanoparticles. Optical absorption measurement revealed strong size dependant resonances that are attributed to the surface plasmon resonance of the Au particles.