Quantitative XPS analysis of high Tc superconductor surfaces

Abstract

The procedure of quantitative XPS analysis involving the relative sensitivity factors is most convenient to apply to high T c superconductor surfaces because this procedure does not require standards. However, a considerable limitation of such an approach is its relatively low accuracy. In the present work, a proposition is made to use for this purpose a modification of the relative sensitivity factor approach accounting for the matrix and the instrumental effects. The accuracy of this modification when applied to the binary metal alloys is 2% or better. A quantitative XPS analysis was made for surfaces of the compounds Bi 2Sr 2CuO 6, Bi 2Sr 2CaCu 2O 8, and YBa 2Cu 3O Y. The surface composition determined for the polycrystalline samples corresponds reasonably well to the bulk stoichiometry. Slight deficiency of oxygen was found for the Bi-based compounds. The surface exposed on cleavage of the Bi 2Sr 2CaCu 2O 8 single crystal was found to be enriched with bismuth, which indicates that the cleavage occurs along the BiO planes. This result is in agreement with the STM studies published in the literature.