ANALYSIS OF OLS CORE-LEVEL OF P-TYPE AND N-TYPE HIGH-T(C) COPPER OXIDES - EVIDENCE FOR A DIFFERENT NATURE OF CARRIER DOPING

A detailed analysis of the O1s core-levels of p- and n-type high-Tc co pper oxides is reported. The binding energies of O1s core-level in La2 -xSrxCuO4 and Nd2-xCexCuO4 are found to be different. We also find tha t, for the p-type La2-xSrxCuO4, the O1s peak shifts towards lower bind ing energy when hole-carriers are introduced, while, for the n-type Nd 2-xCexCuO4, the O1s peak shifts towards higher binding energy when ele ctron-carriers are introduced. Taking into account the different cryst al structures and the chemical environment of oxygen sites, our observ ations are analyzed and explained consistently. It follows that, we ar e able to understand why holes (electrons) can be doped into p- (n-) t ype high-Tc copper oxides. The results also confirm that p- and n-type high-Tc copper oxides are quite distinct in nature.