Auger electron spectroscopy study of copper binding states in YBa 2Cu 3O 7−x monocrystals: effect of high oxygen pressure

Abstract

The Cu L 3M 45M 45 Auger transitions were compared for the oxides CuO and Cu 2O and for YBa 2Cu 3O 7− x monocrystals as grown or annealed at 400°C under 60 atm oxygen pressure. An indication of the presence of copper in other binding states than in copper oxides was found for the YBa 2Cu 3O 7− x monocrystals. Deconvolution of the Cu L 3M 45M 45 spectra allows a clear distinction between copper in the oxidized monocrystal and copper in a non-oxidized monocrystal. Gaussian components found for the superconducting oxide can be interpreted by considering the presence of two copper sites containing two different copper(II) binding states, or copper(II) andcopper(III) binding states. It is also probable that the variations in the L 3M 45M 45 line shapes for YBa 2Cu 3O 7− x and the shifts observed for this transition indicate the mixing of Cu 3d levels with O 2p states.