X-ray Photoemission Measurements Ancl Electronic Structure of Hg]la2~a(h2~6+3

HgBa2CaCu20~s (Hg1212.) thin films g]own epitaxially on SrTi03 (100) substrates have been chemically etched and studied with x-ray photoelectron spectroscopy (XPS). The XPS data presented here are the first on an epitaxial thin film of a mercury cuprate superconductor, the first in which signals from the superconducting phase dominate all the core level spectra, and the first to exhibit a clear Fermi edge in the valence band region. 1 Ig is found tc) be in a single chemical state, contrary to previous reports based on measurements from sintered pcdycrystalline pellets. The Ba, Ca, Cu, and O core levels are similar to those rneasurcd from T1213a?.CaCu20g+~ (’N-2212), which is chemically and structurally most similar to Hg-1 212, and other cuprate superconductors. Despite the similarities in the core level spectra} distinct differences are observed in the valence bands of IIg1212 andTI-2212 which are attributed to differences in the apical oxygen densities of states.