Determination of coordinations and coordination-specific site occupancies by electron energy-loss spectroscopy: An investigation of boron—oxygen compounds

Evidence for boron diffusion into sub-stoichiometric MgO (001) barriers in CoFeB/MgO-based magnetic tunnel junctions

“…We note however that a B 2 Regardless, the formation of mixed oxides at the interface could be attributed to the presence of oxygen vacancies during the deposition of the MgO layer. The O 1s XPS depth profile peak at a BE of 531 eV can be fitted by several components, the main oxide from MgO at $531 eV plus a surface oxide and boron oxide component at the BE of 532.5 eV [20][21][22] both of which are found in every depth scan but with relatively lower intensity as the depth or etching time increases. At the etching time of 8 s, corresponding to the MgO-CoFeB interface, another oxide component at a BE of 531.5 eV is identified; this component is suspected to be an intermixed MgB x O y previously reported by Read et al 20 Oxide components at 54.7 and 61.8 eV in the Mg 2p spectra are present throughout the junction and are identified as Fe and Co oxides, respectively, and these phases give rise to the combined peak in the O 1s spectra at $530 eV at the MgO/CoFeB interface (t ¼ 8 s) and the deconvolved peaks at 530.5 and 530 eV further into the CoFeB layer (t ¼ 12 s).…”

“…The B K-edge in the MgO barrier is characteristic of the trigonal coordination of [BO 3 ] 3À in B 2 O 3 , which exhibits a sharp peak at $194 eV due to the (p*) transition and followed by a broader peak at $205 eV due to the (r*) transition. 22 The intensity of each B K-EEL spectrum in Fig. 3(d) is integrated over a 10 eV energy window after background subtraction and normalisation by a partial scattering crosssection, to give the B relative areal density across the barrier, as shown overlaid on the HAADF image in Fig.…”

Analytical Transmission Electron Microscopy

“…Secondly, the valence of the excited atom can affect the intensity distribution in the ELNES. This predominantly occurs in edges that exhibit considerable overlap between the initial and final states and hence a strong interaction between the core hole and the excited electron leading to the presence of Sauer et al (1993). A comparison of the B K-ELNES from: (a) the mineral vonsenite containing trigonal planar BO 3 groups; (b) the mineral rhodizite containing tetrahedral BO 4 groups and (c) a mixed coordination boron-doped Fe,Cr oxide.…”

Order and Disorder in Boron Phases

“…The identical ELNES features in different compounds allow the rapid determination of the local atomic environment even in complex structures. For example, Sauer et al [22] have applied it to minerals in order to differentiate between planar-trigonal and tetrahedral coordinations of boron with oxygen.…”