Size saturation in low energy ion beam synthesized Au nanoclusters and their size redistribution with O irradiation

Embedded Au nanoparticles have been produced in ordinary silica glass by high dose 32 keV Au− ion implantation. Samples implanted with doses higher than 1 × 1016 cm− 2 are found to show an absorption band peaked around 535 nm, corresponding to the surface plasmon resonance (SPR) of the Au nanoclusters in silica glass. An increase in the SPR peak intensity with increase in dose has been observed upto a dose ∼4 × 1016 cm− 2, after which the absorption intensity shows a saturation. This saturation in the SPR intensity has been explained as coming due to a break up of larger Au nanoparticles formed near the surface by displacement spikes induced by subsequently incident Au ions against their regrowth from the movement of Au atoms towards the surface. Further high dose O implantation at 32 keV has been found to result in a drop in absorption. On the contrary, a 2 MeV O implantation has been found to result in a growth in nanoparticle size resulting in an enhanced absorption.