Doping and dimensionality effects on the core-level spectra of layered ruthenates

Core-level spectra of the Mn-doped Sr₃ Ru₂ O ₇ and Srn+1 Run O3n+1 (n=1, 2, and 3) crystals are investigated with x-ray photoelectron spectroscopy. Doping of Mn to Sr₃ Ru₂ O₇ considerably affects the distribution of core-level spectral weight. The satellite of Ru3d core levels exhibits a substantial change with doping, indicating an enhanced electron localization across the doping-induced metal-insulator transition. However, the Ru3p core levels remain identical with Mn doping, thus showing no sign of doping-induced multiple Ru valences. In the Srn+1 Run O3n+1 (n=1, 2, and 3), the Ru3d core-level spectra are similar, indicating that the chemical bonding environment around Ru ions remains the same for different layered compounds. While the Sr3d shallow core levels shift to higher binding energy with increasing n, suggesting their participation in Sr-O bonding with structural evolution.