  Nickel nitride (Ni-N) thin film samples were deposited using reactive
magnetron sputtering process utilizing different partial flow of N2 (RN2). They
were characterized using x-ray reflectivity (XRR), x-ray diffraction (XRD) and
x-ray absorption near edge spectroscopy (XANES) taken at N K-edge and Ni
L-edges. From XRR measurements, we find that the deposition rate and the
density of Ni-N films decrease due to successively progression in RN2,
signifying that Ni-N alloys and compounds are forming both at Ni target surface
and also within the thin film samples. The crystal structure obtained from XRD
measurements suggest an evolution of different Ni-N compounds given by: Ni,
Ni(N), Ni4N, Ni3N, and Ni2N with a gradual rise in RN2. XANES measurements
further confirm these phases, in agreement with XRD results. Polarized neutron
reflectivity measurements were performed to probe the magnetization, and it was
found Ni-N thin films become non-magnetic even when N incorporation increases
beyond few at%. Overall growth behavior of Ni-N samples has been compared with
that of rather well-known Fe-N and Co-N systems, yielding similarities and
differences among them.
