Nonaqueous chemical etch for YBa2Cu3O7−x

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Abstract
A nonaqueous chemical etch, with Br as the active ingredient, is described which removes the insulating hydroxides and carbonates that form on high‐temperature superconductor surfaces as a result of atmospheric exposure. X‐ray photoemission spectra have been recorded before and after etching YBa2Cu3O7−x films. It is found that, after the etch, the high binding energy O 1s and Ba 3d peaks associated with surface contaminants are greatly reduced, the Y:Ba:Cu ratio is close to the expected 1:2:3, and the oxidation state of the Cu(2+) is not affected. The resistance of an etched film reaches zero at 78 K, compared to 81 K for a similar unetched film. The suitability of other nonaqueous halogen‐based etches is discussed, as is the applicability of this etch to other high Tc superconductors.