Study of reactively sputtered nickel nitride thin films

Nickel nitride (Ni-N) thin film samples were deposited using reactive magnetron sputtering process utilizing the different partial flow of N-2 (R-N2). They were characterized using x-ray reflectivity (XRR), x-ray diffraction (XRD) and x-ray absorption near-edge spectroscopy ()CANES) 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 R-N2, 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 R-N2. 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. (C) 2020 Elsevier B.V. All rights reserved.