Photoemission spectroscopy ofYb3Si5and its connection with Si-Yb interfaces

Angle-integrated photoemission results are presented for ${\mathrm{Yb}}_3$ ${\mathrm{Si}}_5$ taken with synchrotron radiation in the interval 80–450 eV and with Mg Kα radiation. The spectra give evidence of mixed-valence behavior of Yb in the bulk (a valence of 2.52±0.02), while the Yb atoms at the surface and just below the surface are in the divalent state. This is consistent with the 4f compound formation shift which is 1.05 eV for bulk Yb and with the surface compound formation shift which is reduced by a factor of 0.76. The results are compared with those from Si(111)-Yb interfaces annealed at 300 °C and at 450 °C. The valence of the mixed-valence Yb in the interface does not depend on the annealing conditions and its value (2.37±0.02) is lower than in ${\mathrm{Yb}}_3$ ${\mathrm{Si}}_5$. The results are briefly discussed in connection with interface growth problems.