We have studied the molecular orientation of the commonly used organic semiconductor copper phthalocyanine (CuPC) grown as thin films on the technically relevant substrates indium tin oxide, oxidized Si, and polycrystalline gold using polarization-dependent x-ray absorption spectroscopy, and compare the results with those obtained from single crystalline substrates [Au(110) and GeS(001)]. Surprisingly, the 20–50 nm thick CuPC films on the technical substrates are as highly ordered as on the single crystals. Importantly, however, the molecular orientation in the two cases is radically different: the CuPC molecules stand on the technical substrates and lie on the single crystalline substrates. The reasons for this and its consequences for our understanding of the behavior of CuPC films in devices are discussed.

Interface between poly (9,9-dioctylfluorene) and alkali metals: cesium, potassium, sodium, and lithium J.Role of metal-molecule chemistry and interdiffusion on the electrical properties of an organic interface: The Al-F 16 CuPc case Chemical and electrical properties of interfaces between magnesium and aluminum and tris-(8-hydroxy quinoline) aluminum Organic semiconductor interfaces: Discrimination between charging and band bending related shifts in frontier orbital line-up measurements with photoemission spectroscopy

We compare the electronic structure of differently fluorinated copper phthalocyanines (CuPC, CuPCF4, and CuPCF16) using x-ray photoemission spectroscopy and valence-band ultraviolet photoemission spectroscopy. Whereas the ionization potential (IP) is increased by more than 1 eV as a function of the degree of fluorination, further electronic properties such as the optical gap or the composition of the highest occupied molecular orbital and lowest unoccupied molecular orbital remain nearly unchanged. This fact renders these compounds an ideal tool for the investigation of the influence of the IP on the interface properties. At the interface to gold, besides interface dipoles we observe both downward and upward band bending. These phenomena depend clearly on the IP of the phthalocyanines.

The changes of the electronic structure of copper phthalocyanine ͑CuPc͒ caused by the intercalation with potassium are studied using core-level and ultraviolet photoemission spectroscopy. The analysis of the valenceband spectra allows the estimation of the energy gap relevant for transport, which is substantially larger than the energy gap obtained using optical methods, showing that solid CuPc has to be regarded as a correlated material. Furthermore, our experiments indicate that there is structural ͑polaronic͒ relaxation of the CuPc molecules upon charging and that the lowest unoccupied molecular orbital of CuPc is more concentrated in the central part of the phthalocyanine molecules.

We report a study of the electronic structure and charge transfer in the metallofullerene Sc 3 N@C 80 using photoemission and x-ray absorption spectroscopy. Through a comparison of the x-ray absorption spectrum of Sc 3 N@C 80 at the Sc L 2,3 edge with atomic multiplet calculations, the Sc 3d electron count is determined to be 0.6, thus giving an effective Sc valency of 2.4. With the N atom gaining a full electronic shell by means of covalent bonding with the Sc ͑also involving the Sc 3d electron density observed in the x-ray absorption experiments͒, the remaining six valence electrons of the Sc 3 N cluster are then transferred to the carbon cage which stabilizes the C 80 cage structure with I h symmetry, a structure which is not energetically favored in neutral C 80. The presence of the highly symmetric I h cage structure is further supported by the observation of distinct fine structure in the valence band photoemission spectra of the endohedral, which results from the high degree of effective degeneracy of the electronic states in the molecule. Finally, the results of investigations of K-doped Sc 3 N@C 80 using photoemission give insight into the K x Sc 3 N@C 80 phases that are formed upon intercalation.