Under different atmospheric environment composed of pure Ar and N2

a serial of FexN (1.6<x<2.2) samples were made by RF sputtering. Proton depth elastic scattering was adopted to measure Fe

N

O and C

XPS was used to detect the oxidation of iron. Mossbauer spectroscopy was used to analyze the samples as sputtered and annealed after 200℃

250℃ and 300℃. Combined with X-ray diffraction

the results show that: when the ratio of Fe:N is close to 2

its phase structure will undergo a transition from orthogonal ζ -Fe2N and ε -Fe2N--Fe3N to hcp ε -Fe2N

while the first neighbor of Fe atom may be rich of or lack of N. When the nitrogen content is increased during sputtering

or the samples are annealed

Fe2N phase will transform into quasi-ZnS structure.