Superconductivity of Nd1.85Ce0.15CuO4-y by electrochemical oxidation

Superconductivity of n-type superconductor Nd1.85Ce0.15CuO4-y (NCCO) by ele ctrochemical oxidation is reported for the first time and the cyclic voltam mogram curve for NCCO as working electrode is presented. Investigations ind icate that after oxidation, superconductivity of NCCO is improved: T-c is r aised from 20 K up to 26 K, the superconducting volume fraction is increase d also. The valence electronic states of oxygen and copper in NCCO are stud ied by x-ray photoelectron spectroscopy. It is found that the Cu-2p(3/2) pe ak shifts to the higher binding energy side about 0.4 eV, which indicates t hat the valence-state of copper ions is risen up after oxidation. These res ults imply that hole-carriers exist in n-type superconductor.