HRTEM surface profile imaging of superconducting YBa2Cu4O8

Surface profile images have been recorded from high-Tc superconducting YBa2 Cu4O8 using high-resolution transmission electron microscopy. The surface r egions are found to be relatively more stable than those of YBa2Cu3O7. The stability of the double CuO chains in the vicinity of a crystal surface was found to depend on whether or not they were parallel or perpendicular to t he surface in question. Possible mechanisms of the formation of both surfac e structures and near-surface defects are discussed. (C) 2000 Academic Pres s.