Fundamental limits to detection of low-energy ions using silicon solid-state detectors

Recent advances in solid-state detector (SSD) technology have demonstrated the detection of ions and electrons down to 1 keV. However, ions at keV energies lose a substantial amount of energy ΔN in a SSD through Coulombic interactions with target nuclei rather than through interactions that contribute to the SSD output pulse, whose magnitude is a measure of the ion’s incident energy. Because ΔN depends on the ion species, detector material, and interaction physics, it represents a fundamental limitation of the output pulse magnitude of the detector. Using 100% quantum collection efficiency silicon photodiodes with a thin (40–60 Å) SiO2 passivation layer, we accurately quantify ΔN for incident 1–120 keV ions and, therefore, evaluate the detection limits of keV ions using silicon detectors.