Study of near-surface layers modified by ion implantation in Si wafers by grazing incidence X-ray reflectometry

Abstract

Abstract The grazing incidence X-ray reflectivity (GIXR) curves recorded from two sets of Si(111) samples implanted with As+ ions of energy 80 keV with a number of doses above the amorphization limit are reported. The first, ‘clean’ set of samples, was implanted in ultra high and clean vacuum to avoid contamination. The second, ‘contaminated’ set, was implanted under less rigorous conditions, and contaminated with carbon and oxygen. The reflectivities for the ‘contaminated’ samples show that a formation of near-surface layer of lower electron density (about 10–15% for the highest dose) comparing to the pure Si occurs. The thickness of the layer increases with ion dose, and complicated in-depth electron density profiles are necessary to fit the reflectivities. The results for the ‘clean’ samples show quite different, dose dependent, features, and suggest a qualitative change in layer properties occurring between the doses of 1×1016 and 5×1016 I cm−2 . The reflectivity at higher doses indicate a densification of the near-surface layers due to implantation of about 7–12% higher comparing to the pure Si.