Photoemission core level shifts in Gd silicides

Photoemission core spectra from Gd silicides (Gd 3 Si 5 , GdSi and Gd 5 Si 3 ) are presented. With respect to pure crystalline Si the Si 2 p and 2 s levels shift toward lower binding energies as follows: 0.4 eV in Gd 3 Si 5 , 0.7 eV in GdSi and 1.2 eV in Gd 5 Si 3 . On the contrary, the Gd levels (4 f , 5 p , 4 d and 4 p ) do not shift within the experimental sensitivity. The observed shifts are discussed in connection with the available information on the valence electron states of Gd silicides.