Morphology and electronic structure of submonolayer Pb on Si(111)–(6×66×6)Au

The electronic structure and the morphology of Pb adsorbed on the Si(111)–(6×66×6)Au substrate in the coverage range from 0.025 up to 1 monolayer are investigated with ultraviolet photoelectron spectroscopy (UPS) and scanning tunneling microscopy (STM). The UPS measurements reveal two distinct peaks in the spectra. Correlation with the STM images allows us to associate one of them with single Pb atoms. The second peak emerges at coverage of 0.075 ML and is identified as a localized quantum well state. An evolution of these states as a function of the Pb coverage is determined.