ELECTRONIC-STRUCTURE STUDIES OF YBA2CU3OX 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 str ucture 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. D etailed measurements of the Fermi surface for YBa2Cu3O6.9 are presente d and are compared with predictions of band theory. In the metallic re gion of the phase diagram, changes in the Fermi surfaces are measured as a function of oxygen stoichiometry. The electronic structure is mon itored as the oxide changes from a metal to a semiconductor with addit ional oxygen depletion. For intermediate stoichiometries, effects of o xygen-vacancy ordering are considered. Unusual resonant effects observ ed at several photon energies are examined as the oxygen content is va ried.