Deformation yield of Co nanoparticles inSiO2 irradiated with 200 MeV 127I ions

Cobalt ions of 160 keV have been implanted into SiO2 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 I-127 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 x 10(-14) and 3.3 x 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. (C) 2004 Elsevier B.V. All rights reserved.