OPTIMIZATION OF THE DEPTH RESOLUTION IN ERDA OF H USING C-12 IONS

Depth resolution is one important parameter in the depth profiling of H by elastic recoil detection analysis (ERDA). We report on depth reso lution measurements and compare them with those calculated by the DEPT H code [E. Szilagyi and F. Paszti, these Proceedings (IBA-11, Balatonf ured, Hungary, 1993) Nucl. Instr. and Meth. B 85 (1994) 616; E. Szilag yi, F. Paszti and G. Amsel, Nucl. Instr. and Meth. B, to be submitted] . Experimental conditions were determined as precisely as possible: th e straggling in the absorber foil and the effect of its inhomogeneity were directly measured and an analytical approximation of the results was incorporated into the DEPTH code. ERDA depth resolutions were meas ured and calculated on a multilayered Ni-Ti:H sandwich target, with a C-12 beam of 2.55 MeV in different geometrical conditions. Measurement s and calculations agree fairly well. Optimization of depth resolution versus geometry has also been undertaken yielding a near-surface reso lution of approximately 2 nm.