Highly sensitive hydrogen detection by medium energy Ne+ impact

Hydrogen atoms on solid surfaces were measured directly by elastic recoil detection analysis (ERDA) using medium energy (100–150 keV) Ne + ions with an excellent sensitivity of (∼ 1 × 10 12 H/cm 2 ) without any absorber foils and time-of-flight techniques. An electrostatic toroidal analyzer acquired H + ions with energy around 11 keV recoiled from Si(111)-1 × 1-H surfaces. The H + fraction strongly depends upon emerging angle and takes a value more than 50% at the angle below 70° and a saturated value of 17% at the angle above 80° with respect to surface normal. We detected H atoms on the reduced TiO 2 (110) exposed to water molecules at room temperature (2 L) and estimated the absolute amount of H to be ∼ 2.0 × 10 14 H/cm 2 corresponding to ∼ 38% (∼ 0.38 ML) of the bridging oxygen atoms.