Elongation of gold nanoparticles in silica glass by irradiation with swift heavy ions

We examined the mechanism whereby nanoparticles of gold embedded in silica become elongated and oriented parallel to each other on ion irradiation. Elongation occurred for gold particles with radii smaller than 25 nm. The process was simulated by using a thermal spike model. For small-radius nanoparticles, ion irradiation raises the temperature above the melting points of both gold and silica, whereas for larger nanoparticles neither the gold nanoparticle nor the surrounding silica matrix is melted.