Effect of nitrogen doping on the structure of metastable β-W on SiO2

Highlights: • Stabilization of β-W thin films by DC sputtering in Ar/N₂ atmosphere • Increasing nitrogen content stabilizes the β phase but increase porosity • This has an impact on the perpendicular anisotropy of an adjacent CoFeB layer Metastable β-W phase exhibits a large spin Hall effect which has attracted a great interest for spin-orbit torque-based memory applications. Here we study the growth and structure of W films prepared by magnetron sputtering under different argon and nitrogen gas mixture conditions. X-ray diffraction and sheet resistivity show that low argon with low nitrogen gas flow stabilizes the β-W phase in thick films. High argon gas flow promotes the growth of porous β-W films which increases the oxygen content and the resistivity of the films. It is observed that the N₂ doping of the W films reduce the perpendicular magnetic anisotropy of an adjacent CoFeB layer.