Low-temperature gaseous nitriding and subsequent oxidation of epitaxial Ni/Fe bilayers

Low-temperature gaseous nitriding was applied to epitaxial Ni/Fe bilayers deposited onto a MgO(001) substrate. The pore-free nitride layers produced were subsequently oxidized in oxygen. The samples were analyzed by conversion electron Mossbauer spectroscopy (CEMS), x-ray diffraction (XRD), and Rutherford backscattering spectroscopy in combination with channeling techniques. Nitriding in pure NH3 gas at 300 degrees C led to the formation of a textured E-Fe-nitride layer with a predominant composition of Fe2.07N. The epitaxial relationship of the E-Fe-nitride layer with the MgO substrate was found to be epsilon-Fe2.07N{203}(010)//MgO(001)(110). The nitride layer produced was subsequently oxidized in p(O-2) = 100 mbar at 275 degrees C. While the XRD spectra acquired on the oxidized samples revealed the formation of a Fe-oxide phase with a spinel structure, the GEMS spectral lines could not be interpreted in terms of any Fe-oxide or Fe-hydroxide phase know. It is suggested that the peculiarities in the GEMS data are caused by N atoms incorporated into the oxide lattice

Thin Al, Au, Cu, Ni, Fe, and Ta films as oxidation barriers for Co in air

We have investigated the effectiveness of Al, Au, Cu, Ni, Fe, and Ta films with thicknesses up to 4 nm for protecting a Co surface from oxidation in air at room temperature. The distinct change in the Co 2p3/2 core-level line shape observed by x-ray photoelectron spectroscopy upon the oxidation of Co makes it a simple matter to identify the fractions of the Co that are in the metallic state and in the oxidized state. We find that the best choices for protecting Co from oxidation are Al and Ta. We found that Au, which is one of the most popular choices, is not particularly effective for protecting Co

Properties of (Nb-0.35, Ti-0.15)(x)Ni1-x thin films deposited on silicon wafers at ambient substrate temperature

We have studied the properties of (Nb0.35, Ti0.15)xN1−x films deposited by reactive magnetron sputtering at ambient substrate temperature, focusing in particular on the dependence of film properties on the total sputtering pressure. As the pressure increases we observe a transition in the film structure from the ZT to the Z1 structural zone according to the Thornton classification. In general, the superconducting transition temperature (Tc) and residual resistance ratio have a very moderate dependence on total sputtering pressure, while the film resistivity increases an order of magnitude as the sputtering pressure increases. A wide spectrum of material science techniques is used to characterize the films and to explain the relationship between the sputtering conditions and film properties. Transmission electron microscopy and x-ray diffraction analysis show that 160-nm-thick (Nb0.35, Ti0.15)xN1−x films consist of 20–40 nm grains with good crystallinity. Films sputtered under low pressures have a weak [100] texture, while films sputtered under high pressures have a distinct [111] texture. A stable chemical composition and reduction in film density as the sputtering pressure increases indicate that the change of resistivity in the ZT structural zone is due to a variation in the quenched-in vacancy concentration. In contrast voids on the grain boundaries and vacancies together produce the high film resistivities in the Z1 structural zone