Theoretical characterization of the TTF/Au (1 1 1) interface: STM imaging, band alignment and charging energy

Abstract

A detailed density functional study is performed to analyze the TTF/Au (111) interface, including the effect of the molecular charging energy on the transport gap. Theoretical STM calculations are carried out, and compared with recent STM experimental evidence, for a dilute TTF/Au (111) structure in order to validate the interface geometry used in our calculations. We show that the alignment between the metal and the organic levels is mainly controlled by the charge transfer between the two materials, as determined by the difference between the molecule Charge Neutrality Level (CNL), and the initial Fermi level. The calculated transport gap is 4.1eV, and the CNL is found close to the LUMO level, located about 0.7eV from vacuum.