Electronic structure of partially fluorinated copper phthalocyanine (CuPCF4) and its interface to Au(1 0 0)

We present a study of the organic semiconductor copper tetrafluorophthalocyanine (CuPCF4) on single crystalline Au(1 0 0) using photoemission spectroscopy and compare the results to the unsubstituated copper phthalocyanine (CuPC) complex, which is a well-established molecular organic semiconductor. The observed satellite structures in the C 1s core level photoemission spectra are discussed in detail and we show that the fluorination considerably changes the ionization potential while leaving the energy separation of the occupied electronic levels almost unchanged. Concerning the metal/organic interface, we observe the formation of an interface dipole, whereas the observed dipole is very different for CuPCF4 (0.6 eV) and CuPC (1.2 eV). Furthermore, the energy position of the highest occupied molecular orbital with respect to the gold Femi level is similar in both cases.