ELECTRONIC-STRUCTURE STUDIES OF YBA2CU3OX (6.2-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-6.9) USING ANGLE-RESOLVED PHOTOEMISSION

Using high-resolution angle-resolved photoemission, the electronic structure of YBa2Cu3Ox is examined when oxygen stoichiometries are varied in the range 6.2 less-than-or-equal-to x less-than-or-equal-to 6.9. Detailed measurements of the Fermi surface for YBa2Cu3O6.9 are presented and are compared with predictions of band theory. In the metallic region of the phase diagram, changes in the Fermi surfaces are measured as a function of oxygen stoichiometry. The electronic structure is monitored as the oxide changes from a metal to a semiconductor with additional oxygen depletion. For intermediate stoichiometries, effects of oxygen-vacancy ordering are considered. Unusual resonant effects observed at several photon energies are examined as the oxygen content is varied.