Surface morphology and dynamic scaling in growth of iron nitride thin films deposited by dc magnetron sputtering

Iron nitride films were deposited by dc magnetron sputtering using an Ar/N 2 gas mixture. The structure, roughness, and surface morphology of the films were investigated using x-ray diffraction, grazing incidence x-ray scattering (GIXS), and atomic force microscopy (AFM). It was found that the morphologies and structures of the films were influenced by the N 2 fraction. The perpendicular fluctuations in the height h(x,t) of the surface were also analyzed by AFM and GIXS in the light of dynamical scaling approach. The surfaces of the films typically exhibited self-affining structures both in space and in time. The two dependent nontrivial exponents, roughness exponent α and growth exponent β, were determined. For the iron nitride films grown at N 2 fraction of 5%, 10%, and 30%, α≈0.65, 0.56, and 0.39, and β≈0.53±0.02, 0.38±0.02, and 0.29±0.03, respectively. The scaling relationship α+α/β≈2 is obeyed in all samples, which is in agreement with Kardar–Parisi–Zhang universality. The discrepancies between the theoretical foundations of dynamic scaling and experimental results have been discussed as well.