Abstract
Early stages of bubble formation in Czochralski grown, (100)-oriented silicon are investigated by implanting 2 x 10(16) He+ cm(-2) at 20 keV and treating the samples in the temperature range 100-450 degreesC. Elastic recoil detection is used to measure the helium content and depth distribution, while the gas release is studied by thermal desorption spectrometry. To evidence the radiation damage evolution and the defect behavior, the results from Rutherford backscattering spectrometry in channeling conditions, cross sectional transmission electron microscopy, and grazing incidence small angle X-ray scattering are critically analyzed and compared. The study leads to the identification of the steps followed by the defects during annealing and suggests that critical condition for the production of stable bubbles is the presence at low temperature of agglomerates composed of more than four vacancies decorated by helium. This kind of defect offers helium the room necessary to transform into gas phase and confer thermal stability to the bubble embryos.