Deformation yield of Co nanoparticles in SiO2 irradiated with 200 MeV 127I ions

Cobalt ions of 160 keV have been implanted into SiO2 layers at a fluence of 1017 atcm−2 at 873 K. The resulting spherical metallic Co nanoparticles have been in their turn irradiated by 200 MeV 127I ions at between 1011 and 1014 ionscm−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 1012 ionscm−2 and deformation yields of 1.7×10−14 and 3.3×10−14 cm2 have been measured for Co nanoparticles of 7.2 and 15.6 mean diameters, respectively. The results are compared with existing models.