Si p-type (100) samples were co-implanted at room temperature with He+ ions at 30keV with a dose of 1016/cm2 and successively with H+ ions at 24keV with a dose of 1016/cm2. A series of samples was thermally treated for 2h from 100 to 900C at 100C steps to study the evolution of point-like and extended defects by two complementary techniques: positron Doppler broadening spectroscopy and transmission electron microscopy. Depth profiling the samples with a positron beam led to the identification of five different traps and the evolution of their profile distributions with thermal treatments. The positron traps were identified as decorated vacancy clusters of different sizes. Their decoration by implanted ions and in some case by oxygen was probed by coincidence Doppler broadening spectroscopy. Up to 300C annealing temperature positrons probe three distributions of different decorated defects covering regions of the sample down to 400–450nm. Starting from 300C annealing temperature no defects were revealed by positrons in the region next to the peak of the implanted ions distributions positioned around 280nm, where extended defects were expected; this indicated complete filling of the defects by H and He. From 300 to 600C decorated vacancy clusters of different sizes appear progressively in the region below 280nm, with a distribution moving deeper into the sample. Comparison with previous measurements on He-implanted samples points out the chemical action of H. Hydrogen atoms interact with the previous damage by He, producing more stabilized vacancy-like defects distributed through the damage region of the sample. Electron microscopy showed the transformation of the extended defects from platelets to blisters and cavities.

Single-Crystal Silicon Co-Implanted by Helium and Hydrogen - Evolution of Decorated Vacancy-Like Defects with Thermal Treatments. C.Macchi, S.Mariazzi, G.P.Karwasz, R.S.Brusa, P.Folegati, S.Frabboni, G.Ottaviani: Physical Review B, 2006, 74[17], 174120 (12 pages)