Observation of the phase formation in Fe–N films deposited by reactive pulsed laser deposition

Abstract

Fe–N films have been grown on SiO2/Si(100) substrates by reactive pulsed laser deposition (PLD). A series of films was deposited at 20 °C and at 250 °C, with a wide range of nitrogen pressures. Both nitrogen pressure and deposition temperature were found to affect the film average compositions, structures, phase percentages, and magnetic properties of the films. The saturation magnetization of the films is shown to depend not only on their average nitrogen content but also on the phases and their relative amounts that make up the films. In particular, the iron nitrides γ′-Fe4N, and ε-Fe3N (which has a wide range of composition) play a major role in determining the magnetization. Results can be understood in terms of the relative contributions of the deposition rate and atomic surface diffusion in producing thin-film structure. To date, no giant moments larger than Ms of pure Fe have been observed in this investigation.