Fano Resonance of Eu$\text{}^{2+}$ and Eu$\text{}^{3+}$ in (Eu,Gd)Te MBE Layers

Resonant photoemission spectroscopy, with application of synchrotron radiation, was used to study the valence band electronic structure of clean surface of (EuGd)Te layers. Fano-type resonant photoemission spectra corresponding to the Eu 4d-4f transition were measured to determine the contribution of 4f electrons of Eu$\text{}^{2+}$ and Eu$\text{}^{3+}$ ions to the valence band. The resonant and antiresonant photon energies of Eu$\text{}^{2+}$ ions were found as equal to 141 V and 132 eV, respectively and for Eu$\text{}^{3+}$ ions were found as equal to 146 eV and 132 eV, respectively. Contribution of Eu$\text{}^{2+}$4f electrons was found at the valence band edge while for Eu$\text{}^{3+}$ it was located in the region between 3.5 eV and 8.5 eV below the valence band edge.