“…For implantations at the lower energies, at 50-150 keV, the ion source at our laboratory was employed. Concentration profiles of heavy projectiles in low-Z solids can be measured to depths of 1-10~m by Rutherford backscattering spectrometry (RBS) of e's of some MeV energy [2]. Here the specific energy loss figures of the ~ particles are accurate to < 2 % (3), and, consequently, also the ranges derived from the energy spectra.…”