Local Pb Concentration of the Pb/Si(111)–(7 × 7) Wetting Layer Correlated to Kelvin Probe Force Microscopy Measurements

In binary systems of two materials with a different work function, the local work function is believed to depend on the material concentration. For large Pb concentrations, we here confirm a mostly linear relationship between the local work function and the concentration for the Pb/Si(111) system for large Pb concentrations in the regime where Pb islands are not formed. To this end, we evaporate Pb through a half‐space mask onto the Si(111)–(7 × 7) substrate and investigate the resulting penumbra at about 120 K using Scanning Force Microscopy (SFM). We measure the local work function difference by Kelvin probe force microscopy. We expect that the Pb concentration varies mostly linearly with lateral position with deviations near to the end of the range due to the spherical shape of the source. We conclude that the local contact potential difference is indeed proportional to the Pb concentration for large Pb concentrations. This result will allow to calibrate the Pb concentration from Kelvin probe force microscopy measurements in future experiments.