Impact of Potassium Doping on a Two-Dimensional Kagome\nOrganic Framework on Ag(111)

Alkali\nelement doping has significant physical implications for\ntwo-dimensional materials, primarily by tuning the electronic structure\nand carrier concentration. It can enhance interface electronic interactions,\nproviding opportunities for effective charge transfer at metal–organic\ninterfaces. In this work, we investigated the effects of gradually\nincreasing the level of K doping on the lattice structure and electronic\nproperties of an organometallic coordinated Kagome lattice on a Ag(111)\nsurface. With the introduction of K dopants into the 4-fold N–Ag\ncoordinated Kagome lattice, the highly periodic Kagome lattice gradually\ntends to become discrete. Combining synchrotron radiation photoemission\nspectroscopy, scanning tunneling microscopy/spectroscopy, and density\nfunctional theory calculations, we revealed the mechanism of structural\ntransformation of the lattice, i.e., the change in thermodynamically\nfavored structures caused by competition of electron donors. As an\nelectron donor with a lower ionization energy, K adatoms tend to replace\nthe Ag adatoms and form a more thermodynamically stable N–K\ncoordination structure. Moreover, enhanced charge transfer from K\nto the Kagome lattice induced a rigid shift of the Fermi level. Our\ninvestigation provides new insights for the study of alkali-doped\norganometallic nanostructures.