Depth resolution studies in SiGe delta-doped multilayers using ultralow-energy O2 + secondary-ion-mass spectrometry

Abstract

Improvements in depth resolution using low primary ion energy secondary-ion-mass spectrometry have been demonstrated. This comprehensive study is done using a wide range of impact angles at ultralow energies. In this work, using Ge delta-doped Si samples, we confirm that depth resolution can be improved by lowering the primary ion impact energy at ultralow energy. By varying the angle of incidence from 0° to 70°, we noted that a better depth resolution is achievable not only at normal incidence but over a wider range of impact angles as the probe energy is reduced. The best depth resolution was observed using Ep ∼250 eV and θ∼0°-40° with full width at half maximum (FWHM) ∼1.5 nm and λd