Crystallization of optically thick films of Co x Fe 80 − x B 20 : 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 scanning electron microscopy, as well as spectroscopic ellipsometry and magneto-optical Kerr effect spectroscopy for annealing temperatures ranging from 300 to ${600}^{\\ensuremath{\\circ}}\\mathrm{C}$. The transformation of \\ensuremath{\\sim}100-nm-thick ${\\mathrm{Co}}_{x}{\\mathrm{Fe}}_{(80\\ensuremath{-}x)}{\\mathrm{B}}_{20}$ films from amorphous to polycrystalline was revealed by the sharpening of spectral features observed in optical and magneto-optical dielectric functions spectra. The influence of B on the dielectric function was assessed both experimentally 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 was observed, in agreement with the electrical investigations by means of the four-point-probe method.