Charge transfer from Cu in YBa2Cu3O7−δ and Ba2Cu3O4Cl2 crystals determined by Auger electron spectroscopy

Abstract

A formulation is proposed to estimate the charge transfer ΔqCu from Cu to some anions in metal-oxide crystals, using Auger electron spectroscopy. In the formulation, a parameter, the Auger transition probability ω, is introduced, which is defined as the ratio of Auger intensity due to a certain transition to the total Auger intensity due to other transitions when the same core electrons are primarily excited. By applying the formulation to vacuum-cleaved surfaces of YBa2Cu3O7−δ (YBCO) and Ba2Cu3O4Cl2 (BCOC) crystals, we obtained the following results: (1) YBCO cleaves between CuO2 and BaO layers, and the amount of ΔqCu is 2.3 in units of elementary electric charge. The deviation of ΔqCu from 2.0 suggests the existence of Cu3+-like atoms; (2) for BCOC, ΔqCu varies from 3.3 to 1.7 depending on the Ar ion beam sputtering time.

Charge transfer from Cu inCu2Oepitaxially grown on MgO(001) by dc-reactive magnetron sputtering

“…The average operation is supported by the result for YBCO where the agreement with other reports by x-ray photoelectron became better. 1 So ⌬q Cu is 0.34e.…”

“…The current is 2.0ϫ10 Ϫ7 A. The detail of the chemical bonding analysis was described in the previous paper 1 and we briefly explain the main points avoiding the repetition of the full story. We first assume that Auger transition intensity is proportional to the charges of the levels involved in the transition as Weißmann did.…”

“…⌬q Cu for the L 3 M 23 M 23 transition is smaller than ⌬q Cu for the L 3 M 45 M 45 transition as is the case with YBCO and BCOC. 1 We still have no clear explanation and tentatively took the average. The average operation is supported by the result for YBCO where the agreement with other reports by x-ray photoelectron became better.…”