BEHAVIOR OF PB DEPOSITED ON SINGLE-CRYSTAL SURFACE OF BI-SR-CA-CU-O

The clean and modified surfaces of Bi2Sr2CaCu2Oy and Bi2Sr2CuOy single crystals were investigated by LEED and AES. The clean surfaces were found to be composed of the BiO layer and it was strongly modulated with a period of 26 Å (Bi2Sr2CaCu2Oy) and 24 Å (Bi2Sr2CuOy). At the initial stages of Pb deposition, the Auger signal from oxidized Pb was observed and at the later stages beyond half a monolayer, the metallic Pb signal was dominant. From this fact, it was concluded that there were two adsorption sites on the Bi layer, the one being the oxygen occupied site and the other the oxygen vacant site. The sample heating at 200°C promoted the oxidation of Pb without a significant mixing of Pb and Bi. The further heating at 550°C fully removed the deposited Pb from the surface and recovered the original Bi layer. From the LEED result after the monolayer deposition, the modulated structure of Bi layer was found to be persistent, especially in its periodicity, despite the considerable change of surroundings. © 1990.