LAUSR

Abstract High-entropy alloys nitrides (HEA-N) have been proposed as diffusion barriers to prevent metal diffusion. Due to their lack of grain-boundaries and large lattice distortion, HEA-N have lower diffusion than binary nitrides. Despite the interest, very few quantitative studies have been performed to precisely measure metal diffusion in HEA-N. Here we report, for the first time, Fe diffusion rates and activation energy in AlCrTaTiZrN HEA-N thin-films, and demonstrate that they are lower than reported value in TiN. AlCrTaTiZrN was deposited on steel from a metal alloy target using reactive radio frequency sputtering under various nitrogen flow rates. X-ray diffraction shows that as the nitrogen flow rate increases, microstructure of the films changes from amorphous to nanocrystalline. Thermal stability studies at 700–900 °C show that AlCrTaTiZrN remains chemically and structurally stable up to 800 °C. SIMS shows that the HEA-N films are effective barrier layers for Fe diffusion for temperatures up to 800 °C. At higher temperatures, the films are mechanically stable but not effective as barrier films, due to recrystallization in AlCrTaTiZrN. The measured diffusion coefficient is 7 × 10 − 22 m 2 s − 1 at 700 °C, 30 times lower than any polycrystalline nitride barrier reported in literature. The study not only conclusively demonstrate the effectiveness of HEA-N as diffusion barriers, it also provides quantitative data that can be used by engineers to precisely design barrier layers.