Optical constants of Co-Fe-B (Cobalt-iron-boron alloy, CoFeB)
Santos-Amador et al. 2026: thin film; n,k 0.258–43.5 µm
Complex refractive index (n+ik)
Derived optical constants
Conditions
film_thickness: 5.0E-9 substrate: SiO2/Si
Comments
Co20Fe60B20 thin film, 5 nm thick, deposited by RF magnetron sputtering at room temperature on a Si(100) substrate with a nominal 700 nm thermally grown SiO2 layer. A 10 nm Al2O3 capping layer was deposited by RF sputtering without breaking vacuum. Optical constants were determined by spectroscopic ellipsometry. Optical constants for a 20 nm Co20Fe60B20 film are also reported in the reference.
References
A. Santos-Amador, J. Puebla, O. Del Pozo-Zamudio, S. Vazquez-Miranda, and R. E. Balderas-Navarro. Optical constants of Co20Fe60B20 thin films from mid-infrared to ultraviolet-visible for stratified media modeling. Thin Solid Films 839, 140903 (2026) (Numerical data kindly provided by Armando Santos-Amador)
Data
Additional information
About Cobalt-iron-boron alloy
CoFeB is a family of ferromagnetic metallic alloys composed of cobalt, iron, and boron. It is commonly deposited as an amorphous thin film and may partially crystallize during annealing. CoFeB is widely used in spintronic devices, particularly as an electrode material in magnetic tunnel junctions. Its physical and optical properties depend on the elemental composition, film thickness, deposition conditions, and thermal history; therefore, CoFeB does not represent a single fixed stoichiometric compound.
Other names and variations
- Co-Fe-B
- CoFeB
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