The early stages of bubble formation in Czochralski-grown (100)-oriented Si were investigated by implanting 2 x 1016 He+/cm2 at 20keV and treating the samples at 100 to 450C. Elastic recoil detection was used to measure the He content and depth distribution, while the gas release was studied by thermal desorption spectrometry. To reveal the radiation damage evolution and defect behavior, the results of Rutherford back-scattering spectrometry under channeling conditions, cross-sectional transmission electron microscopy and grazing-incidence small-angle X-ray scattering were analyzed and compared. The study led to the identification of the steps followed by the defects during annealing, and suggested that a critical condition for the production of stable bubbles was the presence, at low temperatures, of agglomerates composed of more than 4 vacancies decorated by He. This type of defect offered He the necessary space to transform into the gas phase and confer thermal stability on the bubble embryos.

Early stages of Bubble Formation in Helium-Implanted (100) Silicon. B.Pivac, O.Milat, P.Dubček, S.Bernstorff, F.Corni, C.Nobili, R.Tonini: Physica Status Solidi A, 2003, 198[1], 29-37