Grazing incidence diffuse x-ray scattering investigation of the properties of irradiation-induced point defects in silicon

Point-defect properties in ion-irradiated Si were investigated using in situ grazing incidence diffuse x-ray scattering. Bombardment with 4.5-keV He at 100 K and 3-MeV electrons at 6 K led to the production of Frenkel pairs. These defects are characterized by close-pair configurations and by relaxation volumes of vacancies and interstitials that have nearly the same magnitude, but opposite sign. Thermally activated motion of interstitial atoms occurs above ≈150 K, while that for vacancies occurs above ≈175 K. The motion of interstitials below 150 K during electron irradiation is shown to be induced by electronic excitation, and it is negligible for ion irradiations. Similar results were observed for irradiation with 20-keV Ga and 1.0-MeV Ar, although the defects were already clustered upon bombardment at 100 K. Correlation distances between vacancies and interstitials in cascades are obtained.