A simple coincidence method of deuterium profiling using the D(3He,α)H reaction

A simple standard coincidence arrangement is described for D(3He, α)H depth profiling experiments of deuterium in solids. Both reaction products are detected in coincidence, the high-energy protons being observed in transmission through a foil target. The energy of the α-particles is converted into the corresponding depth scale, whereas the local deuterium concentration is calculated from the yield of the α-particle spectrum. The measurement of α-particles in coincidence with protons allows a reduction of background arising from Rutherford scattering of 3He and other reaction products. For samples of deuterium implanted into Ta2O5 and Er, the method allows a reduction of the backscattering yield by a factor of more than 103. The residual background is due to accidental coincidences. It can be even more reduced using an accurate experimental geometry. The background reduction is largest for samples with a low content of deuterium, allowing measurements of deuterium profiles of 9x1013 D+/cm2 implanted into Ta2O5 at an energy of 8 keV. This corresponds to a maximum deuterium concentration of about 5x10-4 D per Ta2O5. This method is not restricted to thin films, but it allows measurements of deuterium profiles in a thick sample, e.g. of an implantation profile in a 0.4 mm silicon wafer. (orig.)