Journal of Applied Crystallography

Volume 26, Part 4 (August 1993)

research papers

J. Appl. Cryst. (1993). 26, 574-582 [ doi:10.1107/S0021889893001748 ]

Reduction of the interfacial diffusion in Ni-Ti neutron-optics multilayers by carburation of the Ni-Ti interfaces

M. Mâaza, B. Farnoux, F. Samuel, C. Sella, F. Wehling, F. Bridou, M. Groos, B. Pardo and G. Foulet

Abstract: It is shown that it is possible to reduce both interfacial diffusion and interfacial roughness in neutron-optics Ni-Ti multilayered monochromators. This is achieved by the deposition of an ultrathin layer of carbon at the Ni-Ti interfaces. A comparison between treated Ni-Ti multilayers and an untreated one was performed by grazing-angle neutron reflectometry and completed by grazing-angle X-ray reflectometry, Auger electron spectroscopy and secondary-ion mass spectrometry. More specifically, the experimental data show that nickel diffuses into the titanium layers in the untreated multilayers. This diffusion decreases when the Ni-Ti interfaces are separated by 10 Å of carbon. Moreover, the results show that this Ni-Ti multilayer quality is better if the glass substrate is also treated with 30 Å amorphous carbon. The reflectivity of the first Bragg peak R_B(k = 1) is lower than the theoretical one (68%) but increases slightly from 18 to 25% after the carburation of the interfaces.