AN ANALYSIS OF THE BUBBLE FORMATION BEHAVIOR UNDER DIFFERENT EXPERIMENTAL CONDITIONS

In an effort to further the understanding of the nucleation mechanisms as well as processes such as gas diffusion and dissociation, the experimental data on temperature dependencies of bubble density obtained under different experimental conditions are compiled and analysed. In particular, the effects of parameters such as helium concentration, helium generation rate, annealing time and displacement damage rate on the measured bubble densities are considered. The results are analysed in terms of nucleation and coarsening models. The analysis shows that the low temperature regime is diffusion controlled whereas the high temperature regime is gas dissociation controlled. In the high temperature regime, the large difference in the observed bubble density between the hot-implantation/irradiation and the cold-implantation followed by annealing experiments seems to be associated with large differences in the density (or pressure) of helium within bubbles in the embryonic and developed state, respectively. Furthermore, in this temperature regime, the effective generation rate of helium is identified to be the most important parameter (in addition to temperature) for bubble nucleation. The lack of data in the low temperature regime makes it obvious that further studies are needed to understand the details of the nucleation and coarsening behaviour in this regime.