Influence of Ca doping on X-ray photoelectron core-level spectra of magnetoelectric bulk BiFeO3

The X-ray photoelectron spectrum (XPS) core-level spectra of pristine and doped bulk BiFeO3, namely Bi0.9BaxCayFeO3 with x + y = 0 and 0.1 were recorded on the Ar+-ion sputtered sample surface at room temperature. Afterward, the obtained XPS spectra of Bi 4f, Fe 2p, O 1 s, Ba 3d and Ca 2p levels were inspected using the symmetric Gaussian-Lorentzian product function, to study the influence of the spin-orbit coupling and/or electrostatic interactions on these spectra. Our findings show all elements have a single valence state (except Bi) with the allowed spin-orbit splitting energy (Delta) for their valence of Bi3+, Fe3+, O2-, Ba2+, and Ca2+. Here, the fraction of Bi atoms was converted into Bi-metal Bi-o, due to the Ar+-ion sputtering process. Interestingly, the Fe3+ 2p(3/2) spectra of these samples were fitted well with four Gupta-Sen multiplets, due to the combined electrostatic and spin-orbit interactions. Particularly, the chemical pressure induced by Ca doping considerably influences the Fe3+ 2p(3/2) spectra of BiFeO3, due to the change in the FeO6 octahedra tilting and the change in the position of Fe cations upon Ca doping. So, the edge of the valence band of the Ca-doped BiFeO3 materials shifted toward the Fermi level by about similar to 0.7 +/- 0.1 eV when compared to BiFeO3.

Automated summary

The XPS core-level spectra of pristine and doped bulk BiFeO3 were analyzed to study the influence of spin-orbit coupling and electrostatic interactions. The Ca doping induced chemical pressure significantly impacted the Fe3+ 2p(3/2) spectra of BiFeO3, leading to shifting of the valence band edge of the Ca-doped BiFeO3 materials towards the Fermi level.