Unoccupied Electronic States and Surface Phenomena for YBa2 Cu3 O6.9.

摘要

Inverse photoemission was used to probe the unoccupied electronic levels within 25 eV of E/sub F/ for the high temperature superconductor YBa sub 2 Cu sub 3 O/sub 6.9/. Our results show that the density of states is low from E/sub F/ to /approximately/3.7 eV. Large emission features appearing at 6.5 eV and 8.6 eV are associated with Ba 5d- and Y 4d-derived bands, respectively, while structure at 14 eV above E/sub F/ is due to localized Ba 4f states. Energy dependent studies reveal a dispersive band between /approximately/4 and /approximately/6 eV above E/sub F/. An oxygen-induced feature was observed at 1.8 eV, but there is no evidence that high-energy electron-stimulated-desorption removes these chemisorption states. (ERA citation 14:019876)