Analysis by X-ray photoelectron spectroscopy of LnBa2Cu3O7−x: The significance of fine structure in the O 1s and Ba 3d envelopes

Observations by X-ray photoelectron spectroscopy on LnBa 2 Cu 3 O 7−x (Ln = Y and Ho) show that there are no significant surface electronic differences as a result of substitution of Y by Ho. The O 1s and Ba 3d envelopes exhibit fine structure which appears to be related to significant electronic and structural properties of the 1-2-3 compounds. Namely, the low-binding-energy component of the O 1s envelope is due to Ba─o bonding as well as being specific to the electronic linkage of the Cu layers in the orthorhombic structure. The anomalous low-binding-energy contribution to the Ba 3d envelope suggests that Ba may play an important electronic role as well as a structural role. There is further evidence that Sr and Ca play similar roles in the related Bi─Sr─Ca─Cu─O high-T c compounds.