Tetra-t-butyl magnesium phthalocyanine on gold: electronic structure and molecular orientation

In this work we have investigated the electronic structure and the molecular orientation of (t-Bu)(4)PcMg (tetra-t-butyl magnesium phthalocyanine) on polycrystalline and single crystalline gold substrates using photoemission spectroscopy and x-ray absorption spectroscopy, and we compare the results to the unsubstituted PcCu (copper phthalocyanine). The C 1s photoemission spectrum is described similar to unsubstituted relatives with an additional component for the aliphatic substituents. The variation of the excitation energy causes distinct differences in the shape of the C 1s spectrum, which is very useful for the analysis of the molecular orientation in the uppermost layer. It is shown that despite of the sterically demanding substituents, ordered sublimed films of (t-Bu)(4)PcMg are accessible, the orientation of the molecules, however, is different from the orientation of the unsubstituted relatives.     

Core-level photoelectron study of indium chains on Si(1 1 1) at 10 K

High-resolution core-level data from the prototypical In/Si(1 1 1) system have been acquired at 10 K. An asymmetric tail in the In 4d spectra reveals a metallic character of the low temperature Si(1 1 1)8 × 2 phase confined to the inner indium rows. The decoupling of the one-dimensional inner indium chains from any metallic environment at ∼10 K suggests a possible Luttinger liquid behavior. At room temperature essentially a broadening of the spectral features is noticed, which appears compatible with a fluctuation scenario.     

Joys and pitfalls of fermi surface mapping in Bi(2)Sr(2)CaCu(2)O(8+delta) using angle resolved photoemission

On the basis of angle-scanned photoemission data recorded using unpolarized radiation, with high (E,k) resolution, and an extremely dense sampling of k space, we resolve the current controversy regarding the normal state Fermi surface (FS) in Bi(2)Sr(2)CaCu(2)O(8+delta). The true picture is simple, self-consistent, and robust: the FS is holelike, with the form of rounded tubes centered on the corners of the Brillouin zone. Two further types of features are also clearly observed: shadow FSs, which are most likely to be due to short range antiferromagnetic spin correlations, and diffraction replicas of the main FS caused by passage of the photoelectrons through the modulated Bi-O planes.     

Silver on copper phthalocyanine: Abrupt and inert interfaces

The chemistry and electronic structure evolution were studied upon the formation of the interfaces between copper phthalocyanine and Ag and Sn deposited on it in ultra high vacuum conditions. The measurements were performed by means of high-resolution photoemission spectroscopy of core-levels and the valence band, and using synchrotron-radiation facilities. The investigations demonstrate the formation of chemically inert and abrupt interfaces.     

The dielectric function of potassium-doped zinc-phthalocyanine

We have studied the electronic excitations of potassium-doped zinc-phthalocyanine using electron energy-loss spectroscopy. This allowed the determination of the complex dielectric function ε(ω) in an energy range between 0 and 70 eV. Our results reveal distinct changes of the electronic excitation spectra going from ZnPc to K₄ZnPc. They can be used as data basis for future optical characterization of potassium-doped ZnPc films. PACS 71.20.Rv; 78.20.-e     

Charge transfer at F<Subscript>16</Subscript>CoPc and CoPc interfaces to Au

We analyze the electronic properties of the interfaces between cobalt phthalocyanine (CoPc), as well as fluorinated cobalt phthalocyanine (F₁₆CoPc), and an Au(100) single-crystal using X-ray photoemission spectroscopy and valence band ultraviolet photoemission spectroscopy. Our data demonstrate that for the monolayers of both materials a charge transfer occurs from the substrate to the center of the organic molecules resulting in a central Co(I) ion. This leads to the conclusion that this effect essentially is fluorination- and ligand-independent.     

Stripe correlations in Na(0.75)CoO2

We present a combined high-energy x-ray diffraction and local-density approximation study of the sodium ordering in Na(0.75)CoO2. The obtained results rule out previously proposed Na-ordering models and provide strong evidence for the formation of sodium-density stripes in this material. The local-density approximation calculations prove that the sodium-density stripes lead to a sizable dip in the density of the Co states at the Fermi level, pointing to band structure effects as a driving force for the stripe formation. This indicates that the sodium ordering is connected to stripelike charge correlations within the CoO2 layers, leading to an astonishing similarity between the doped cuprates and the NaxCoO2 compounds.     

Potassium induced phase transition of FePc thin films

We have studied the structure and stoichiometry of potassium doped iron phthalocyanine (FePc) films using a combination of electron diffraction and core level excitation studies. We show that iron phthalocyanine undergoes structural phase transitions upon potassium addition, which can be described by the formation of two potassium doped phases with K2FePc and K4FePc composition.     

Electronic structure of the organic semiconductor copper phthalocyanine: experiment and theory

The electronic structure of the organic semiconductor copper-phthalocyanine (CuPc) has been determined by a combination of conventional and resonant photoemission, near-edge x-ray absorption, as well as by the first-principles calculations. The experimentally obtained electronic valence band structure of CuPc is in very good agreement with the calculated density of states results, allowing the derivation of detailed site specific information.