We used scanning tunneling microscopy and spectroscopy to reconsider three-atomic-layer Pb islands with two types of pattern grown on Si(111) surface. Our results demonstrate that the pattern on the island surface appears as the superposition of geometric corrugation and local variation of the electronic structure. The former originates from two kinds of interface relaxation, resulting in two types of periodic distortion of the lattice. The latter is due to the periodic strength modulation of quantum-well states in Pb islands, causing inhomogeneity in the integration of the density of states and the bias-dependent pattern. This strength modulation of the quantum-well states can be attributed to the electronic screening effect induced by the lattice distortion in Pb islands.
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