Local nanostructuring of gold thin films through dewetting induced by Ga+ irradiation

Dewetting of ion-irradiated metal films is a consequence of the local melting occurring during the irradiation. In this study we present the dewetting evolution of Au thin films bombarded with Ga+ ions in a focused ion beam system, pointing out the different surface patterns observed in films having different starting thickness and morphology. In fact, in ion-irradiated films thicker than 2 nm the typical features of dewetted liquids appear, i.e. enlarging dry holes surrounded by metal interconnections. On the other side, a different behavior is observed in thinner discontinuous films, where a dense distribution of circular nanoparticles is formed upon irradiation. We studied the dependence of Au nanoparticles distribution obtained for different ion energies and fluences, determining that a maximum fluence of ∼2 × 1014 Ga/cm2 can be used to achieve a monomodal distribution of nanoparticles with regular shape, before detrimental effects of sputtering occur.