Nonaqueous chemical depth profiling of YBa2Cu3O7−x

A nonaqueous solution of Br in absolute ethanol (EtOH) has recently been reported [R. P. Vasquez, B. D. Hunt, and M. C. Foote, Appl. Phys. Lett. 53, 2692 (1988)] to be effective at removing nonsuperconducting surface species from YBa2 Cu3 O7−x films, leaving the surface close to the ideal stoichiometry. This same etchant is shown here to be an effective bulk etchant in chemical depth profiling through 1-μm-thick films. The Cu remains in the 2+oxidation state and the stoichiometry, as determined by x-ray photoelectron spectroscopy, is close to ideal and nearly constant throughout the profile, indicating the absence of any large preferential etching effects. The reaction of YBa2 Cu3 O7−x films with HF/EtOH, HCl/ EtOH, and I/EtOH solutions is also reported.