Investigation of the Processes of the Formation of a Nonequilibrium Phase-Structural State in FeTiB Films Obtained by Magnetron Sputtering

Abstract

The main trends in the modern development of magnetic microelectronics are miniaturization and operation speed, while ensuring efficient operation in the MHz and GHz frequency ranges of magnetic fields. Creating new magnetic materials characterized by properties providing these trends is the most important fundamental and applied problem of materials science. In this regard, nanocrystalline soft magnetic alloys belonging to Fe–Me–X systems (Me is one of the metals of the IVb group of the periodic table; X is one of the light elements N, C, O, or B) obtained in the form of films attract great attention. Such films produced by magnetron sputtering and characterized by the Fe/MeX two-phase structure are capable, as was shown earlier by the authors of the present article using the example of Fe–Zr–N films, of providing a combination of high saturation induction Bs, low coercive field Hc, and high hardness and thermal stability of the structure. The films were prepared by magnetron sputtering. In accordance with the initial data obtained by the authors, the films of the FeTiB system can provide better properties as compared with FeZrN films. The published data on FeTiB films in the context of their application in microelectronic devices are very sparse. In the present work we continue studies of FeTiB films aimed at identifying the chemical and phase composition providing the level of properties required for the application of the films in microelectronics. The nanocrystalline films containing from 0 to 14.3 at % Ti and from 0 to 28.9 at % B are obtained by DC magnetron sputtering. The phase-structural state of the films is studied by X-ray diffraction and transmission electron microscopy. According to the phase composition, all films are divided into three groups: single-phase (supersaturated solid solution of Ti in α-Fe), two-phase (α-Fe(Ti)/αTi, α-Fe(Ti)/TiB2, α-Fe(Ti)/FeTi, and α‑Fe(Ti)/Fe2B), and XRD amorphous. The XRD amorphous films are shown to be characterized by a mixed structure made of a solid solution α-Fe(Ti) with a grain size in the range from 0.7 to 2 nm and an amorphous phase. A reasonable assumption has been made that the amorphous phase is enriched by boron. A quantitative assessment of the grain size of the α-Fe(Ti) phase and its dependence on the chemical and phase composition of the films is given. The mechanisms of solid-solution and dispersion strengthening determine the grain size of this phase.