X-ray reflectance studies of interface in ion beam sputtered CoFeB/MgO bilayers

Abstract

This letter reports specular and diffuse x-ray reflectance studies of the interface in the ion beam sputtered CoFeB(∼5–8 nm)/MgO(∼2–5 nm) bilayers. The study reveals the specific roles of oxygen ion energy, substrate temperature, and reactive gas ambient on controlling the interface width in the bilayers. Depending on oxidation-method employed for MgO growth the interface width varies between 0.51 and 0.20 nm. Energy of assist ions (≤50 eV) plays a key role compared to the growth temperature in determining the sharpness of the interface. The bottom grown CoFeB exhibited significant increase in coercivity (HC), which also depends on MgO-growth process.