A compact high-resolution elastic recoil detection system for lithium depth profiling

A compact high-resolution elastic recoil detection analysis (ERDA) system was developed for precise Li analysis. 200-400 keV He+ ions were used as primary ions and the energy spectra of recoiled Li ions were measured using a magnetic spectrometer. Due to its dispersion the background originating from the scattered primary ions is reduced. The recoiled ions of the substrate other than Li, which may also contribute to the background, were rejected by a thin mylar foil placed in front of a focal plane detector. An electrostatic quadrupole lens was installed at the entrance of the magnetic spectrometer to improve the depth resolution by correcting the effect of the kinematic broadening. The performance of the developed high-resolution ERDA was examined by measuring several samples. A thin Li layer (1.5 × 1015 cm−2) deposited on a graphite surface was clearly observed and the detection limit was estimated to be less than 0.01 ML under typical measurement conditions. The depth resolution was estimated to be 0.5 nm at the surface and was better than 3 nm in the surface region within 5 nm from the surface.