Kinetic study of group IV nanoparticles ion beam synthesized in SiO2

Most studies concerning group IV (Si, Ge) ion beam synthesized nanocrystals in SiO2 have shown that a link exists between the observed physical properties and the characteristics of the "populations" of nanoparticles (size-distribution. density, volume fraction). The aim of this paper is to study the influence of the initial supersaturation and annealing conditions on these characteristics. For this, experimental methods have been developed, that allow accurate statistical studies. Different transmission electron microscopy (TEM) imaging conditions have been tested and the most adequate ones have been identified for each system. An original method for the measurement of the density of precipitates embedded in an amorphous matrix has been developed and tested for Ge precipitates in SiO2 and has permitted to evidence a conservative Ostwald ripening during annealing. The kinetic behavior of Si nanoparticles has also been studied by coupling TEM measurements and "atomistic" simulations. During annealing, the growth of these nanoparticles is very slow but their size significantly increases when increasing the initial Si excess. Simulations are in perfect agreement with experiment when taking into account interaction effects between particles. (C) 2001 Elsevier Science B.V. All rights reserved.