Distinct variation of electronic states due to annealing in T′ -type La1.8Eu0.2CuO4 and Nd2CuO4

We performed Cu {\it K}-edge X-ray absorption fine structure measurements on T'-type La$_{1.8}$Eu$_{0.2}$CuO$_4$ (LECO) and Nd$_2$CuO$_4$ (NCO) to investigate the variation in electronic state associated with emergence of superconductivity due annealing. The near-edge spectra as-sintered (AS) LECO are quite similar those AS NCO, indicating that ground is a Mott insulator. found significant at sites electron density after annealing ($n_{\rm AN}$) was evaluated for both superconducting non-superconducting NCO be 0.40 0.05 electrons per Cu, respectively. In but not extended analysis revealed softening strength Cu-O bond CuO$_2$ plane annealing, which consistent screening effect phonons metallic state. Since amounts oxygen loss ($\delta$) comparable each other, these results suggest distinct electron-doping processes two compounds. That approximately follows relation $n_{\rm AN}=2\delta$ can understood if doped through deficiency, anneal-induced nature large AN}$ band causes self-doping carriers. origin difference doping discussed connection size charge transfer gap.