Tailoring shape of CeO2 nanoparticles by swift heavy ion irradiation

Abstract

The structural response of CeO₂ nanoparticles to swift heavy ion irradiation was studied using transmission electron microscopy complemented with numerical methods combining the Monte Carlo code TREKIS and molecular dynamics. The result of electronic excitations of model cubic nanoparticles differs from that of bulk and infinite film targets due to competing effects: reduced energy deposition due to electron emission, and increased lattice energy gain in nanoclusters <20 nm in size because of the confinement of slow electrons by grain boundaries. Ion impacts into nanoparticles smaller than 15 nm induce partial or complete melting, significantly changing their shape. It was demonstrated experimentally and numerically that lattice damage on the edges of nanoparticles manifests as erosion and emission of atoms and atom clusters. Ion passage through nanoclusters results in the formation of empty or partially empty nanochannels in contrast to irradiation of infinite thin films of the same thickness, inducing formation of nanohillocks on the surface.