Optical characterization of surface and interface oxygen content in YBa2Cu3O/sub x/

Because YBa2Cu3O/sub x/ exists over a range of oxygen content and low oxygen material is nonsuperconducting, it is important to be able to measure and control this parameter for application purposes. We present an optical technique for determining oxygen loss at surfaces and interfaces, where processing and contacts with other materials may affect composition and where usual techniques are insensitive. Using a strong absorption feature at 4.1 eV which appears at low oxygen composition, we find that overlayers of Al and In remove oxygen from YBa2Cu3O/sub x/, but Ag, Au, and room-temperature exposure to moderate vacuum do not