Shape deformation of embedded metal nanoparticles by swift heavy ion irradiation

an invited paper of SHIM 2008Swift heavy ions (SHI) induce high densities of electronic excitations in narrow cylindrical volumes around their path. These excitations have been used to manipulate the size and shape of noble metal nanoparticles embedded in silica matrix. Films containing noble metal nanoparticles were prepared by magnetron co-sputtering techniques. SHI irradiation of films resulted in the formation of prolate Ag nanoparticles with major axis along the ion beam direction. It has been observed that the nanoparticles smaller than the track size dissolve and other grow at their expense, while the nanoparticles larger than track size show deformation with major axis along the ion beam direction. The aspect ratio of elongated nanoparticles is found to be the function of electronic energy loss and ion fluence. Present report will focus on the role of size and volume fraction on the shape deformation of noble metal nanoparticles by electronic excitation induced by SHI irradiation. The detailed results concerning irradiation effects in silica-metal composites for dissolution, growth and shape deformation will be discussed in the framework of thermal spike model

Formation of Nanostructures with a Controlled Size Distribution in Si-based Gels by Ion Irradiation

Studies of irradiation effects in inorganic polymers and gels performed at CSNSM during the past 10 years are overviewed and examples of precipitations with interesting applications (C, Si, metals) occurring during the conversion into ceramics are presented. The precipitation yield, as a function of irradiation fluence or annealing conditions, and particle physical properties were investigated by means of various techniques, depending on their nature. The rates of gel-to-ceramics conversion and of precipitation are determined by the density of electronic excitations produced by ion irradiation (collision cascades slightly assisting the diffusion of metal atoms). Particles formed by ion irradiation show a narrower range of sizes and consequently more interesting characteristics for magnetic or optical applications than those formed in heat-treated gels