REDUCTION OF THE INTERFACIAL DIFFUSION IN NI-TI NEUTRON-OPTICS MULTILAYERS BY CARBURATION OF THE NI-TI INTERFACES

It is shown that it is possible to reduce both interfacial diffusion a nd interfacial roughness in neutron-optics Ni-Ti multilayered monochro mators. This is achieved by the deposition of an ultrathin layer of ca rbon at the Ni-Ti interfaces. A comparison between treated Ni-Ti multi layers and an untreated one was performed by grazing-angle neutron ref lectometry and completed by grazing-angle X-ray reflectometry, Auger e lectron spectroscopy and secondary-ion mass spectrometry. More specifi cally, the experimental data show that nickel diffuses into the titani um layers in the untreated multilayers. This diffusion decreases when the Ni-Ti interfaces are separated by 10 angstrom of carbon. Moreover, the results show that this Ni-Ti multilayer quality is better if the glass substrate is also treated with 30 angstrom amorphous carbon. The reflectivity of the first Bragg peak R(B)(k = 1) is lower than the th eoretical one (68%) but increases slightly from 18 to 25% after the ca rburation of the interfaces.