MEDIUM-ENERGY ELASTIC RECOIL ANALYSIS OF SURFACE HYDROGEN

We describe a technique for the detection of light mass constituents at or near the surface of a material using two microchannel detectors to time the individual recoils. Sensitivity to hydrogen is demonstrated by probing samples of Kapton, hydrated titanium, and wafer grade silicon with 270 keV helium, neon, and argon ions. Because the detector is sensitive to particle velocity rather than energy, recoil atoms and scattered ions are easily distinguished. Processes which affect the system's sensitivity to hydrogen are identified and a value for the hydrogen detection efficiency is established. The method may realize a number of advantages over conventional elastic recoil detection, including the elimination of the absorber foil, heightened sensitivity, and improved depth resolution.