Study of sputtered particles from gold nano-islands due to MeV self-ion irradiation

Very thin films of gold deposited on silicon substrates form isolated nano-island structures due to the non-wetting nature of gold. Thick films are more homogeneous and do not have the isolated island structures. Thin gold films of various thicknesses (∼0.4-21.4 nm) are deposited under high vacuum condition and irradiated with 1.5 MeV Au2+ ions. The sputtered particles are collected on catcher grids (carbon coated) during the irradiation and are analyzed with transmission electron microscopy (TEM) and Rutherford backscattering spectrometry (RBS). The average sputtered particle size is determined from TEM measurements, whereas the amount of gold on the catcher grid is found by RBS. The average sputtered particle size from thin (up to a thickness of ∼2 nm) discontinuous films is larger compared to the average particle size from thick continuous films. The coverage of the sputtered particles on the catcher grids is also discussed. Energy spike and its distribution in the nano-islands is proposed to be the main reason for the variation in the particle size and the coverage of the sputtered particles on the catcher grid