Gold, copper and gold/copper bimetallic nanoparticles obtained by focused ion beam sputter deposition and rapid thermal annealing

Gold, copper and gold/copper thin layers were obtained in FIB/SEM system by Focused Ion Beam sputter deposition. Layers deposited on SiO2/Si and quartz substrates were subjected to Rapid Thermal Annealing (RTA) in vacuum at 1100 °C. One minute annealing of 20 nm thick films leads to formation of nanoparticles with average size of ∼20 nm but does not change the morphology of 170 nm Au and 180 nm Cu films. Implantation of Ga ions into SiO2/Si substrate before deposition of ∼20 nm Au layers has a strong effect on the nanostructures formed after 1 min annealing. Implantation at 30 kV for 1 and 2 min leads to formation of arbitrary shape nanoislands, which are much larger than the nanoparticles outside of the implanted region. Increase of the implantation time to 4 and 16 min leads to formation of large spheres, the size of which increases with the implantation time. The observed Ga effect is explained by the lower melting temperatures of Au/Ga and Cu/Ga binary alloys and by increased nanoparticle mobility, which favors the coalescence process. Gold nanoparticles with size of ∼20 nm obtained by RTA on control quartz substrate showed local surface plasmon resonance at 535 nm.