Study of formation of Cu nanoparticle using Swift heavy ions

Abstract

In this paper, we present the use of keV and MeV ion beam irradiations and post-irradiation annealing to form Cu nanoparticles in fused silica glass. The sequence of process being: low energy irradiation of fused silica substrate, Cu thin film coating, SHI irradiation and annealing. Fused silica substrates were irradiated using 30 keV argon ions at fluences of 1 × 10¹⁷ ion/cm². 10 nm Cu films were deposited on the low energy irradiated fused silica. These thin films coated fused silica samples were then irradiated using 120 MeV Ag⁹⁺ ions at fluences ranging from 4 × 10¹³ to 1 × 10¹⁴ ion/cm². The irradiated samples were subjected to isochronal annealing in argon gas flow from 400 K to 1200 K for 30 min. The average sizes of Cu nanoparticles were estimated from optical absorption spectra using Mie's theory. The sizes of the Cu nanoparticles were also confirmed from GAXRD and TEM measurements. Post-irradiation annealing results indicate that the formation of Cu₃ nanocluster is favored at annealing temperature of about 700 K. High temperature annealing at 1200 K causes the formation of Cu₄ clusters as well as Cu nanoparticles (larger clusters). After annealing at 1200 K, for the sample 120 MeV Ag⁹⁺ irradiated with high dose (1 × 10¹⁴ ion/cm²) only Cu nanoparticles are formed. The study suggests that irradiation induced defects provide nucleation sites for the formation of nanoparticles, latent tracks provide fast diffusion channels for Cu and, annealing provides required energy for the diffusion.