Experimental study on fabrication technique of a Ni/Ti supermirror using the electron beam evaporation system

Basic study on the fabrication technique of a Ni/Ti supermirror using the v acuum evaporation system with an electron gun has been carried out to impro ve the neutron reflectivity. The substrate roughness dependency to the reflectivity was investigated usi ng polished glass Boats with different surface roughnesses using neutron re flectometry. It was concluded that the substrate roughness in the order of several sub-nanometers was very sensitive to the neutron reflectivity of th e Ni/Ti supermirror. The reflectivity was improved to 80% for the Ni/Ti sup ermirror with an effective critical angle of 2 times that of natural nickel using fine polished glass substrate with a surface roughness of 0.51 nm rm s. The effect of oxidizing Ni and Ti layers to the neutron reflectivity, which were deposited by changing the oxygen gas conditions in the chamber, was i nvestigated. The oxidation effect prevents the deformation of the Ni/Ti sup ermirror structure, and the reflectivity shows an increase of almost 20% fo r the Ni/Ti supermirror with an effective critical angle of 2.6 times that of natural nickel by depositing in an atmosphere of oxygen gas with a parti al pressure of 1x10(-5) Torr. From the depth profile by X-ray photoelectron measurement (XPM) and neutron reflectometry results, it was concluded that the reflectivity increase by oxidation mentioned is caused by decreasing the interface roughness and the interfacial diffusion between Ni and Ti layer, and it is not caused by for ming a NiO compound which increases the scattering potential of the Ni laye r.