On the evolution of the steady state in gold-silica nanocomposites under sustained irradiation

We investigate the kinetic evolution of a nanocomposite submitted to sustained irradiation. The study focuses on gold nanoparticles embedded within a silica host matrix. Irradiations with 4 MeV Au ⁺⁺ ions are performed in the temperature range from 300 K to 1100 K and for fluences up to 8 × 10¹⁶cm^-2. The experimental results are combined with kinetic Monte Carlo simulations to fully characterize the kinetic evolution of the nanoparticles under irradiation. In particular, the change of the steady state with the temperature is investigated in details. First, we demonstrate the existence of a direct-coarsening regime at high temperature, e.g., above 900 K, and of a coarsening-resistant regime at low temperature, e.g., below 700 K. Second, we show that the transition between these two regimes takes place in a temperature region, where the nucleation of new nanoparticles is hindered, and the mass is redistributed among the existing nanoparticles. We also use our experimental results to critically analyze the existing theoretical models. As it has recently been pointed out that the physical principles underlying precipitation under irradiation are similar to those that govern the behavior of driven alloys, this work can be considered as an attempt to bridge the gap between two fields of experimental and theoretical studies, viz., those on driven alloys and those on metal-glass nanocomposites submitted to a sustained irradiation.