Ultrathin Pb film growth on Cu(111) studied by photoemission

The valence bands and the Pb 5d, Cu 3p core levels of Pb films evaporated on Cu(111) were measured by synchrotron radiation photoemission and characterized by low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES). The variation of the surface state at the center of the surface Brillouin zone (SBZ) of Cu(111) with Pb coverage shows that the submonolayer Pb grows on Cu(111) at room temperature (RT) as two-dimensional (2D) islands. With the Pb coverage increasing, the Pb 5d5/2 core level shifts to higher binding energy monotonically. While the Cu 3p3/2 core level is shifted toward higher binding energy by about 120 meV due to the deposition of 1.0 ML Pb. At low Pb coverage, subsequent annealing at 200°C gives rise to Pb–Cu surface alloy formation in the first layer of Cu(111). The Pb 5d core level is shifted toward Fermi level by 20~30 meV due to the surface alloying. An assumption about electron charge transfer from Cu to Pb was adopted to interpret the observed core level shifts.