IN-SITU HYDROGEN CONCENTRATION MEASUREMENTS IN MULTILAYERS USING NEUTRON REFLECTIVITY

We show that neutron reflectivity is very useful for in situ hydrogen concentration measurements in thin films, as will be demonstrated for Fe/Nb multilayers. The samples consisting of [26 Angstrom Fe/X Angstro m Nb]n with X = 15 Angstrom - 40 Angstrom were charged with hydrogen from the gas phase at different pressures at 473 K. The hydrogen conce ntration in the Nb layers (no hydrogen is dissolved in re) can be dete rmined from the change in the scattering contrast between Nb and Fe an d the expansion of the Nb lattice due to the uptake of hydrogen. Both features are clearly visible in the reflectivity diagrams.