HRTEM surface profile images of Bi₂Sr₂CaCu₂O₈

Surface profile images of Bi2Sr2CaCu2O8 have been obtained using high-resolution electron microscopy. The cleaved (001) surface of the crystals terminates with a single Bi-O atomic layer. The modulated structure developed in this surface atomic layer was observed directly. The (hk0) surfaces were found to decompose in air into an amorphous coating layer. This coating layer was unlikely recrystallized into the original structure under electron beam irradiation. The amorphous layer on the (hk0) surface formed in pure Ar atmosphere was relatively thin and could be recrystallized into some secondary phases in which a Bi loss was observed. The original (001) surface might also be covered by an amorphous-like layer. This disordered layer could be recrystallized under electron beam irradiation into BiSr2Ca2Cu3O9, BiSr2CuO5, etc. which intergrow with the parent crystal perfectly on the (001) planes.