Two stages in the kinetics of gold cluster growth in ion-implanted silica during isothermal annealing in oxidizing atmosphere

The growth kinetics of gold clusters, formed by ion implantation in silica, is experimentally investigated. Isothermal sample annealing at 900 degreesC is performed in air atmosphere for increasing time intervals in the range between 0.5 and 12 h. Two different scaling laws of the cluster average radius with time, t(1/2) and t(1/3), are evidenced, proving that coarsening, i.e., Ostwald ripening, follows the stage of diffusion limited cluster growth, as the annealing time interval increases. By a comparative analysis of the two regimes of cluster growth, in the framework of linearized models for clustering processes, the value of the surface tension of gold nanoparticles in silica matrix has been evaluated. (C) 2002 American Institute of Physics.