Non-contact atomic force microscopy investigation of the (1 x 1) and (root 3 x root 3) phases on the Pb/Si(111) surface

The (1 x 1) and (root 3 x root 3) phases of the Pb/Si(111) surface are investigated at room temperature using noncontact atomic force microscopy. The topographic height difference between these phases is determined to be 1.6 +/- 0.1 angstrom, which is larger than the theoretical value (1.2 angstrom previously predicted. Kelvin probe force microscopy measurements show that the work function on the (1x1) region is 201 +/- 16 meV higher than that on the (root 3x root 3) region. The effective dipole moments by electron transfer from the first layer Si atom to the Pb adatom on the (1x1) phase is discussed. We also succeed in obtaining atomically resolved images of the two phases, and demonstrate that the (1 x 1) phase has small atomic corrugation compared with the (root 3 x root 3) phase when imaging at same tip condition and the same acquisition parameters.