Growth, structural, and magnetic properties of iron nitride thin films deposited by dc magnetron sputtering

FeN thin films were deposited on glass substrates by dc magnetron sputtering at different Ar/N2 discharges. The composition, structure and the surface morphology of the films were characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and atomic force microscopy (AFM). Films deposited at different nitrogen pressures exhibited different structures with different nitrogen contents, and the surface roughness depended on the mechanism of the film growth. Saturation magnetization and coercivity of all films were determined using superconducting quantum interference device, which showed that if N2/(Ar+N2) flow ratio was equal to or larger than 30% the nonmagnetic single-phase γ″-FeN appeared. If N2/(Ar+N2) flow ratio was less than 10%, the films consisted of the mixed phases of FeN0.056 and γ′-Fe16N2, whose saturation magnetizations were larger than that of α-Fe. If N2/(Ar+N2) flow ratio was 10%, the phases of γ′-Fe4N and ε-Fe3N appeared, whose saturation magnetizations were lower than that of α-Fe.