Formation and decay kinetics of nickel nitrides resulting from nitrogen ion implantation. The nickel-nitrogen phase diagram

Structural transformations in nickel films exposed to N+ ions were investigated through the use of electron diffraction, electron microscopy, Rutherford backscattering (RBS) of He+ ions, thermal desorption spectroscopy (TDS). With an increasing exposure dose, there occurred a smooth transition of the FCC structure of Ni to the HCP phase alpha-Ni3N with the lattice parameters a = 0.266 nm and c = 0.430 nm. The completion of the transition was observed once the implanted nitrogen concentration corresponding to the stoichiometric ratio of Ni3N was attained, this giving evidence for the chemical nature of the structural change observed. During annealing, structure variations were traced, enabling one to observe the following four nickel nitrides: (1) alpha-Ni3N with a disordered arrangement of nitrogen atoms (HCP-phase with a = 0.266 nm and c = 0.430 nm), (2) beta-Ni3N with an ordered arrangement of nitrogen atoms (two hexagonal lattices: one with a = 0.266 run, c = 0.430 nm, and the other with a = 0.466 mn and c = 0.43 nm), (3) Ni4N having a primitive cubic lattice structure with a = 0.377 nm, (4) Ni8N having the FCC structure with a = 0.725 nm. The results of an investigation have led to building up a phase diagram for the Ni-N system. (C) 2004 Elsevier B.V. All rights reserved.