Electron Irradiation Effects On The Nucleation And Growth Of Au Nanoparticles In Silicon Nitride Membranes

The formation of Au nanoparticles (NPs) in Au+ ion-implanted silicon nitride thin films and membranes was investigated as a function of post-implantation thermal treatments or room temperature electron irradiation at energies of 80, 120, 160, and 200 keV. The samples were characterized by Rutherford Backscattering Spectrometry and Transmission Electron Microscopy. High-temperature thermal annealing (1100 degrees C, 1 h) resulted in the formation of Au particles with a mean diameter of approximate to 1.3 nm. In comparison, room-temperature electron irradiation at energies from 80 to 200 keV caused the formation of larger Au particles according to two growth regimes. The first regime is characterized by a slow growth rate and occurs inside the silicon nitride membrane. The second regime presents a fast growth rate and starts when Au atoms become exposed to the back free surface of the membrane. Realistic binary electron-atom elastic collision cross-sections were used to analyze the observed nanoparticle growth and membrane sputtering phenomena. The results obtained demonstrate that binary electron-atom elastic collisions can account for the microstructure modifications if the critical displacement energies for the sputtering of N and Si atoms are around 14 +/- 3 eV, and the displacement energy for surface located Au atoms is approximately 1.25 +/- 0.2 eV. Irradiation experiments using focused electron probes demonstrate that the process provides fine control of nanoparticle formation, resulting in well-defined sizes and locations. Published by AIP Publishing.