High Potassium Concentrations Nested in Epitaxial Monolayers of a Flexible Lander-Type Molecule on Ag(111)

Abstract

The structural, electronic, and optical properties of organic adlayers can be tuned to a large extent by incorporating metal atoms. Naturally, the tunability of those properties is limited by the thermodynamic stability of the intercalated phases obtained and the segregation tendency, which often prevents the nesting of high metal atom concentrations in homogeneous epitaxial compound films. Here, we employ scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED) to investigate monolayers of the polycyclic aromatic hydrocarbon tetraphenyldibenzoperiflanthene (DBP, C64H36) epitaxially grown on Ag(111) and intercalated with potassium. This lander-type molecule contains four phenyl substituents that are nearly perpendicular to the aromatic backbone, and its flexibility enables rather complex adlayer structures. We succeeded in preparing highly ordered (mixed) monolayers with up to six potassium atoms per DBP. For increasing K concentrations we find that DBP changes its shape from a consi...