Gold nanoparticles resist deformation by swift heavy ion irradiation when embedded in a crystalline matrix

We have attempted to deform, by swift heavy ion irradiation, gold nanoparticles embedded in crystalline AlAs which resists amorphization. AlAs was first implanted with 1.3 MeV Au ions at room temperature to a fluence of 2 × 1016 cm−2. Rapid thermal annealing (RTA) at 600 °C for 1 or 2 min was used to grow Au nanoparticles in the matrix. Deformation was attempted by 30 MeV Cu5+ irradiation at liquid nitrogen temperature. Crystal damage of the matrix was studied using Rutherford backscattering spectrometry in channeling configuration and Raman spectrometry. The morphology of Au nanoparticles was investigated by Transmission Electron Microscopy.It was found that, in spite of some crystal damage, the AlAs remained crystalline throughout the experiment and spherical Au nanoparticles with size distribution between 2 and 12 nm were observed with no indication of elongation. Thus, high energy heavy ion irradiation does not deform spherical Au nanoparticles embedded in AlAs. This supports the suggestion that the deformation of the gold nanoparticles which has been observed for particles embedded in amorphous materials is a consequence of the hammering deformation of the matrix surrounding the nanoparticles.

► Gold nanoparticles embedded amorphous silica deform under swift heavy ion irradiation.
► We show that such deformation does not occur in AlAs, a crystalline embedding medium.
► Hammering deformation of the matrix is essential for gold nanoparticle elongation.