Electronic structure of clean and Ag-covered single-crystalline ${\mathrm{Bi}}_2$${\mathrm{Sr}}_2$${\mathrm{CuO}}_6$

Photoemission studies of single-crystalline samples of ${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{CuO}}_6$ show clear resemblance to the corresponding data for single crystals of ${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{CaCu}}_2$ ${\mathrm{O}}_8$. In particular, a sharp Fermi-level cutoff, giving evidence of metallic conductivity at room temperature, as well as single-component O 1s emission and Cu 2p satellites with a strength amounting to about 50% of that of the main Cu 2p line, are observed. An analysis of the relative core-level photoemission intensities shows that the preferential cleavage plane of single-crystalline ${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{CuO}}_6$ is between adjacent Bi-O layers. Deposition of Ag adatoms causes only weak reaction with the Bi and O ions of the ${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{CuO}}_6$ substrate, while the Cu states rapidly react with the Ag adatoms, as monitored by a continuous reduction of the Cu 2p satellite intensity as the Ag overlayer becomes thicker.