Electronic structure of ceramics and thin-film samples of high T c Bi2Sr2CaCu2O8+δ superconductors: Effects of Ar+ sputtering, O2 exposure, and Rb deposition

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Abstract
The electronic structure of bulk, and, for the first time, thin‐film samples of the new class of high Tc Bi2Sr2CaCu2O8+δ superconductors, is investigated by photoemission spectroscopy using synchrotron radiation. Ar+ sputtering and Rb deposition result in disrupted Bi O bonds and subsequent change in the valency of Bi, while oxygen adsorption or annealing in oxygen is found to restore the Bi O bonds. The results also show that adsorbates of O2 and/or Rb readily give rise to a number of new oxygen states in the valence band of Bi2Sr2CaCu2O8+δ. The Ar+‐sputtered film is found to be more sensitive to adsorbates of O2 and Rb than the scraped bulk sample, as monitored by the Bi 5d core shifts and the oxygen‐induced valence‐band states.