Surface Phase Nucleation of Lead Monoatomic Layers on Si(111) Induced by Manganese Phthalocyanine Molecules

Hybrid interfaces where organic molecules are adsorbed on metallic substrates are very interesting to understand the fundamental interactions that might modify the chemical–physical properties of molecules or substrate. Here, we explore the adsorption of manganese phthalocyanines (MnPcs) on different structural phases of a Pb monatomic layer, namely, the √7 × √3-Pb and the striped incommensurate phase (SIC-Pb) phase, grown on Si(111). Surprisingly, the deposition of a minute amount of MnPc molecules (∼0.18 molecules/100 nm²) nucleates a macroscopic structural transition of the √7 × √3-Pb phase into the SIC-Pb phase. Our combined scanning tunneling microscopy, low-energy electron diffraction, and density functional theory study revealed that the mechanism behind this surface transformation is related to a strong and local molecule–substrate interaction. The structural phase transition is finally driven by the strained nature of the Pb phases and the energetic stability of the MnPc/SIC-Pb/Si(111) system with respect to the MnPc/√7 × √3-Pb/Si(111) one. The molecule–substrate interaction found in the present study is stronger than the one observed on Pb(111) bulk or thin films, highlighting the implication of the Pb/Si(111) interface in the interaction process. Hence, our results reveal that playing with the substrate dimensionality to tune the molecule–substrate coupling has strong impact on the electronic/magnetic properties of organic hybrid systems.