A study of the surface structure of deposited Au on Pb film

Using low-temperature scanning tunnelling microscopy/scanning tunnelling spectroscopy and in situ reflection high-energy electron diffraction, the surface structure of deposited Au on Pb film was investigated. We observed two types of Moire patterns, the first is formed by Au2Pb with Pb(111) reconstruction (Pb-) with an average period of 2.4 nm; the second is formed by AuPb2 with a Pb- layer with an average period of 5.8 nm. Such a surface structure changes the boundary condition of electrons confined in the Pb film. Moreover, using the structural model proposed, it consumes three monolayers (3 ML) of Pb and reduces the film thickness. These results explain well the phase shift in the oscillation of physical properties of the Pb film, which strongly depends on film thickness by the quantum size effect.