Sputtered Fe1−x(N1−yCy)x films obtained in various (Ar–N2–CH4) reactive plasmas

The Fe1−x(N1−yCy)x iron carbonitrides commonly encountered with high non-metal content are the ε (x = 0.25–0.33) and ζ (x = 0.33–0.36) phases whose structures derive from the ones existing in the binary Fe–N system by substituting N by C. As it is possible to synthesize cubic γ″ and γ‴ iron nitrides with an atomic nitrogen content x close to 0.5, we study here the possibility to substitute N by C to obtain carbonitrides close to an equiatomic non-metal content. Fe1−x(N1−yCy)x films were deposited on copper substrates using a triode sputtering magnetron mode with an iron target in a variable reactive Ar–N2 and/or –CH4 mixture. Energy Dispersive X-ray Analysis was used to determine their composition. The as-sputtered states were identified by X-Ray Diffraction. The target being magnetic, we propose a particular geometry allowing its sputtering. ure (Ar–N2) reactive plasma (y = 0), the atomic nitrogen content x in the films increases linearly from 0 to 0.51 with the N2 flowing rate and then stays constant. The successive nitrides, ε-Fe3N, ζ-Fe2N and a mixture of γ″ and γ‴ can be identified. However, some diffraction peaks remain not indexed using the previous phases. In a pure (Ar–CH4) reactive plasma (y = 1), the atomic carbon content x in the films increases rapidly and linearly from 0 to 0.62 as a function of the CH4 flowing rate while structure changes from α-Fe to χ-Fe5C2 via ε-Fe3C and then to an amorphous compound. ariable (Ar–N2–CH4) reactive plasma, Fe1−x(N1−yCy)x ternary films keeping x close to 0.5 with various y values within the range 0–0.46 are obtained. The crystalline carbonitrides detected by X-Ray Diffraction evolves from a γ″/γ‴ mixture for y = 0 to ζ for y = 0.41–0.46 passing through a ζ/γ‴ mixture for y = 0.33.