How do high energy heavy ions shape Ge nanoparticles embedded in SiO2?

Crystalline Ge nanospheres embedded in SiO2 where irradiated at room temperature with fluences from 1x1015 to 4x1015 cm-2 of energetic J7+ ions. The spheres transform into amorphous oblate-like Ge nanoparticles, with the short axis aligned to the ion beam direction. This ion beam shaping is similar to that of free silica spheres, but differs from the prolate-like ion beam shaping of Au spheres embedded in SiO2.