Perylene-3,4,9,10-tetracarboxylic Dianhydride Molecules Research Articles

The Franck–Condon effect in 1 1B 1u state of 3,4,9,10-perylenetetracarboxylic-dianhydride

The high-resolution laser-induced fluorescence (LIF) electronic spectrum associated with the 1 1A g→1 1B 1u transition in the perylenetetracarboxylic-dianhydride (PTCDA) molecule is discussed in terms of time-dependent density functional theory at TD-B3LYP/4-31G and TD-B3LYP/cc-pVDZ levels. It is shown that the simple vibronic model based on the displaced harmonic oscillators leads to quite reasonable agreement with the LIF experiment, even if some discrepancies occur. The results of TD-B3LYP/cc-pVDZ computations are compared to those obtained earlier within density-functional tight-binding (DFTB) approximation. We argue that the DFTB approach is inadequate to account correctly for the observed intensity distributions in the absorption spectra associated with the 1 1A g→1 1B 1u transition in the PTCDA molecule.

Low energy electron diffraction of the system In-[perylene-3,4,9, 10-tetracarboxylic dianhydride] on MoS2

The system In-[perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA)] on MoS2, prepared by the sequential evaporation of PTCDA and In on a cleaved MoS2 surface, was studied by low energy electron diffraction. The result indicates that reaction products form an ordered structure on the MoS2 surface. From the analysis of the diffraction pattern, the presence of six symmetry-equivalent domains of an oblique unit cell of In-PTCDA species results with the dimensions of 9.5 Å, 16.3 Å, and an enclosed angle of 80.2°. In addition, splitting in two domains by a mirror plane exists with the rotation angle R=±10.8° with respect to each of the three equivalent surface crystal axes of the MoS2 substrate. The new structure is explained by assuming that four In atoms are chemically bonded to the four carbonyl groups of the PTCDA molecules. Furthermore, it is concluded that the In4PTCDA species become tilted after a chemical reaction between the PTCDA molecules and the In atoms, which is in agreement with results previously obtained by angle-resolved ultraviolet photoemission experiments.

Interfacial chemistry of perylene-3,4,9,10-tetracarboxylic dianhydride during the initial stages of film growth on InAs(1 1 1)A

X-ray photoelectron spectroscopy (XPS) and high resolution electron energy loss spectroscopy (HREELS) have been used to investigate the initial stages of film growth of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) on InAs(1 1 1)A substrates. XPS measurements show that the binding energies of the C 1s and O 1s core levels are considerably lower in sub-monolayer films compared to those observed in thicker films, suggesting significant charge transfer at the PTCDA/InAs interface. HREELS results at low film thickness also indicate some interaction as evidenced by a substantial red shift in the carbonyl stretching frequency of the molecules, although there is no molecular fragmentation. The results suggest that the PTCDA molecules in the first monolayer undergo significant interaction with the substrate, with charge transferred from the In-terminated surface to the carbonyl groups of the PTCDA molecules.

Strong K-induced changes in perylene-tetracarboxylic-dianhydride films on Ag(1 1 0) studied by HREELS and LEED

Using high-resolution electron energy loss spectroscopy (HREELS) and low energy electron diffraction (LEED) we have studied the strong structural, electronic, and vibrational changes occurring in K-“doped” films of perylene-tetracarboxylic-dianhydride (PTCDA) on Ag(1 1 0) as a function of K concentration and annealing temperature. Two major phase transitions were observed in the vibrational and electronic excitations as well as in the LEED patterns. At low K-coverages (∼0.5 K/PTCDA) mainly structural changes are observed. Enormous changes occur for K-concentrations of 1 to 2 K atoms per PTCDA molecule which are tentatively attributed to the formation of a charge transfer complex leading to a semiconductor–metal transition. This state is characterized by a drastic intensity increase of vibrational modes at 392, 532, 1042, 1210 and 1540 cm −1 and two low-energy electronic excitations at 0.6 and 0.9 eV, which are tentatively assigned to K 2(PTCDA) and K(PTCDA) complexes. The second transition, perhaps a metal–semiconductor transition, occurs at higher K concentration and/or annealing temperature and is correlated with the abrupt disappearance of the prominent spectroscopic features related to the charge transfer state.

Polarized optical absorption spectra of orientation aligned vanadyl phthalocyanine films

Optical absorption spectra (400∼900 nm) of vanadyl phthalocyanine (VOPc) films deposited on perylenetetracarboxylic dianhydride (PTCDA) films formed on mica (VOPc/PTCDA/mica) depended on orientation of polarization plane of incident light. This means that orientations of VOPc and PTCDA molecules in VOPc/PTCDA/mica align. Since the absorption spectrum of the VOPc film with thickness 100 nm in the VOPc/PTCDA/mica formed at 60 °C corresponded to that of I-TiOPc, structure of the VOPc film was supposed to be close to I-TiOPc. Without the PTCDA film, orientation aligned II-VOPc film was formed on mica kept at 100 °C. © 1997 Elsevier Science S.A. All rights reserved.

A combined STM, LEED and molecular modelling study of PTCDA grown on Ag(110)

Perylene-3,4,9,10-tetracarboxylic-dianhydride (PTCDA) was commensurably grown on Ag(110) by organic molecular-beam deposition (OMBD) under ultra-high vacuum conditions at 5 × 10 −8 Pa. In the monolayer regime, an epitaxial superstructure exists in a single domain orientation, as investigated with low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). Molecular modelling calculations result in the same commensurate structure and provide, in addition, the absolute position of the adsorbate relative to the silver surface. As a result, the flat-lying PTCDA molecules are orientated in the (001) direction of the Ag(110) unit cell, leaving small holes with three uncovered silver atoms between the molecules.

Chemistry and electronic properties of metal-organic semiconductor interfaces: Al, Ti, In, Sn, Ag, and Au on PTCDA.

The chemistry and electronic properties of interfaces formed between thin films of the archetype molecular organic semiconductor 3, 4, 9, 10 perylenetetracarboxylic dianhydride (PTCDA) and reactive and nonreactive metals are investigated via synchrotron radiation photoemission spectroscopy. In, Al, Ti, and Sn react at room temperature with the anhydride group of the PTCDA molecule, producing heavily oxidized interface metal species and thick interfacial layers with a high density of states in the PTCDA band gap. The penetration of the reactive metal species in the PTCDA film is found to be inversely related to their first ionization energy. The noble metals Ag and Au form abrupt, unreacted interfaces. The chemical and structural results correlate well with the electrical properties of the interfaces that show Ohmic behavior with the reactive metal contacts and blocking characteristics with the noble metals. The Ohmic behavior of the reactive metal contacts is ascribed to carrier hopping and/or tunneling through the reaction-induced interface states. \textcopyright{} 1996 The American Physical Society.