Ion beam heating of kinetically constrained nanomaterials

The gallium ion beam heating on electron transparent transmission electron microscopy (TEM) samples of Au/Ni bilayer films supported by SiO₂ substrates was studied by in-situ TEM combined with energy dispersive X-ray spectroscopy. Brief Ga⁺ ion beam irradiation during sample transfer inside the focused ion beam instrument was found to induce dewetting of bilayer films. The observed morphological changes of the metal films are complemented by considerable Au diffusion through the underlying polycrystalline Ni film and adsorption at the Ni/substrate interface. In-situ heating experiments confirm that alterations of the metal bilayer films caused by ion beam irradiation are consistent with thermal annealing at 400 °C for several minutes in the absence of any ion bombardment. Ion beam damage effects equivalent to prolonged heating may pose considerable limitations to ion beam microscopy of samples with reduced dimensions. Ex-situ lift-out procedures of electron transparent samples in the absence of any ion beam irradiation lead to successful conservation of sample morphologies.