Deformation yield of Co nanoparticles in SiO 2 irradiated with 200 MeV 127I ions

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Cobalt ions of 160 keV have been implanted into SiO 2 layers at a fluence of 10 17 at cm −2 at 873 K. The resulting spherical metallic Co nanoparticles have been in their turn irradiated by 200 MeV 127I ions at between 10 11 and 10 14 ions cm −2 at 300 K. The latter procedure induces an increase of the particle size for lower fluences and a deformation for higher fluences. The modification of particle size and shape has been followed by transmission electron microscopy. An incubation fluence for Co nanoparticle deformation of a few 10 12 ions cm −2 and deformation yields of 1.7 × 10 −14 and 3.3 × 10 −14 cm 2 have been measured for Co nanoparticles of 7.2 and 15.6 mean diameters, respectively. The results are compared with existing models.