Crystallization of optically thick films of CoxFe80−xB20: Evolution of optical, magneto-optical, and structural properties

CoFeB alloys are highly relevant materials for spintronic applications. In this work, the crystallization of CoFeB alloys triggered by thermal annealing was investigated by x-ray diffraction techniques and scanningelectron microscopy, as well as spectroscopic ellipsometry and magneto-optical Kerr effect spectroscopy forannealing temperatures ranging from 300 to 600◦C. The transformation of∼100-nm-thick CoxFe(80−x)B20filmsfrom amorphous to polycrystalline was revealed by the sharpening of spectral features observed in optical andmagneto-optical dielectric functions spectra. The influence of B on the dielectric function was assessed bothexperimentally and by optical modeling. By analyzing the Drude component of the optical dielectric function,a consistent trend between the charge-carrier scattering time/resistivity and the annealing temperature wasobserved, in agreement with the electrical investigations by means of the four-point-probe method.