Energy dependent saturation width of swift heavy ion shaped embedded Au nanoparticles

The transformation of Au nanoparticles (NPs) embedded in $SiO2$ from spherical to rod-like shapes induced by swift heavy ion irradiation has been studied. Irradiation was performed with $A197u$ ions at energies between 54 and 185 MeV. Transmission electron microscopy and small angle x-ray scattering measurements reveal an energy dependent saturation width of the NP rods as well as a minimum size required for the NPs to elongate. The NP saturation width is correlated with the ion track diameter in the $SiO2$⁠. NP melting and in-plane strain in the irradiated $SiO2$ are discussed as potential mechanisms for the observed deformation.