On the fabrication of micro- and nano-sized objects: the role of interstitial clusters

Ion-induced bending phenomena were studied in free-standing nano-sized Al cantilevers with thicknesses in the range of 89-200 nm. The objective is to present a predictive and useful model for the fabrication of micro- and nano-sized specimens. Samples were irradiated in a Tescan Lyra dual beam system with 30 kV Ga+ ions normal to the sample surface up to a maximum fluence of similar to 2 x 10(21) m(-2). Irrespective of thickness, all samples bent initially away from the Ga+ beam; as irradiation proceeded, the bending direction was reversed. The Al cantilever bending behavior is discussed in terms of depth-dependent volume change due to implanted Ga atoms, radiation-induced point defects and interstitial clusters. A kinetic model is designed which is based on a set of rate equations for concentrations of vacancies, interstitial atoms, Ga atoms and clusters of interstitial atoms. The bending crossover is explained by the formation of sessile interstitial clusters in a zone beyond the Ga+ penetration range. Model predictions agree with our experimental findings.