An investigation was made of the surface chemistry of superconducting YBa2Cu3O7-ó using high-resolution electron microscopy. Specimens crushed in air exhibited a thick so-called amorphous coating, which would not recrystallize into the bulk structure under electron beam annealing. Instead oxide microcrystals formed within the coating. The amorphous coating layers were reduced to less than half of their original thickness when the specimens were crushed in argon, and were found to recrystallize into the YBa2Cu3O7-ó structure under the same conditions, with atomically clean surfaces produced and observed directly in the profile images. It was also found that the (001) surface terminated with a Cu-O chain. Surface reconstruction with a double atomic layer of Cu covering the (113) and (112) surfaces was confirmed by computer simulation of the profile images.

HREM Studies of Surface Chemistry of Superconducting Cu3Ba2YO7-δ. W.Zhou, D.A.Jefferson, W.Y.Liang: Superconductor Science and Technology, 1993, 6[2], 81-90