X-ray photoelectron spectroscopy of Nd2−xCexCuO4−y (x=0 and 0.15) thin films

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Abstract
Electronic structure of Nd2−xCexCuO4−y (x=0 and 0.15) thin films was examined by x‐ray photoelectron spectroscopy. The films were prepared by rf magnetron sputtering and successive annealing under reducing condition (reduction). The reduced films showed semiconducting and superconducting behaviors depending on the value x. The Cu, O, and Nd core‐level spectra revealed that the doped electrons were predominantly in CuO2 plane of the Nd2CuO4 crystal. The Cu core‐level spectra from x=0.15 films before and after the reduction suggested that the reduction added electrons to Cu4s‐O2p extended conduction band, and strengthened Cu O bond covalency to screen the core hole state by mobile itinerant electrons.