Determination of the hydrogen sensitivity and depth resolution of medium-energy, time-of-flight, forward-recoil spectrometry

Medium energy time-of-flight forward recoil spectrometry has been developed recently as a complement to conventional ion beam analysis methods such as nuclear reaction analysis and elastic recoil detection. Here we report measurements of the minimum detectable surface concentration and near surface depth resolution for hydrogen by forward recoil spectrometry using a number of beam species and energies. The primary physical limitations encountered in these measurements are identified and discussed. Using an 810 keV Ar3+ beam, H on a carbon substrate can, in principle, be detected at areal densities as low as 1 x 1013 H/cm2. A 540 keV O2+ beam has been found to be a suitable choice for depth profiling of H in Si achieving a resolution of approximately 6 nm near the surface. Examples are given which demonstrate the utility of the technique for hydrogen profiling. (orig.)