Coexisting Charge States in a Unary Organic Monolayer Film on a Metal.

Abstract

The electronic and geometric structure of tetracene films on Ag(110) and Cu(110) has been studied with photoemission tomography and compared to that of pentacene. Despite similar energy level alignment of the two oligoacenes on these surfaces revealed by conventional ultraviolet photoelectron spectroscopy, the momentum-space resolved photoemission tomography reveals a significant difference in both structural and electronic properties of tetracene and pentacene films. Particularly, the saturated monolayer of tetracene on Ag(110) is found to consist of two molecular species which are, despite having the same orientation, electronically very different- while one molecule remains neutral, another is charged due to electron donation from the substrate.