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Title: Molecular adsorption and multilayer growth of pentacene on Cu(100): Layer structure and energetics

Abstract

We used the partial charge tight binding method to perform a full structure optimization to determine equilibrium adsorption geometries, energetics, and local charge redistribution for molecular adsorption and multilayer growth of pentacene on Cu(100). We found that single molecule adsorption induces only a localized perturbation of the metal lattice which is limited to the topmost layers. At saturation coverage four stable topologies (Brick, Wave, Lines and Zigzag) were identified, all based on pentacene molecules lying flat on the metal surface and with the central phenyl ring adsorbed in top position. Only two (Brick and Wave) out of the four structures are able to sustain multilayer growth. In both cases, assembling beyond the second layer corresponds to a transition from the flat to a tilted geometry, in which the pentacenes adopt a face-plane-face arrangement leading to a herringbone structure. The energetics of the different structure are reported as a function of the molecular number density of the pentacene multilayer by calculating cohesive, stress, and electrostatic energies. The dominant tilted molecular orientation in the pentacene multilayer is in agreement with the average tilt angle of 65 deg. between the molecular plane and the Cu surface derived by near edge x-ray absorption spectroscopymore » of a four monolayer pentacene film deposited on Cu(100)« less

Authors:
 [1];  [2]; ;  [1]
  1. CNR, Institute of Complex Systems, Sez. Montelibretti, Via Salaria, Km. 29.3, 00016 Monterotondo Scalo (Italy)
  2. (Italy)
Publication Date:
OSTI Identifier:
20957812
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 75; Journal Issue: 15; Other Information: DOI: 10.1103/PhysRevB.75.155401; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ABSORPTION SPECTROSCOPY; ADSORPTION; COPPER; GEOMETRY; LAYERS; MOLECULES; ORGANIC SEMICONDUCTORS; PENTACENE; SURFACES; THIN FILMS; X-RAY SPECTROSCOPY

Citation Formats

Satta, M., Dipartimento di Fisica dell'Universita di Roma 'La Sapienza', Piazzale Aldo Moro 5, 00185 Rome, Iacobucci, S., and Larciprete, R.. Molecular adsorption and multilayer growth of pentacene on Cu(100): Layer structure and energetics. United States: N. p., 2007. Web. doi:10.1103/PHYSREVB.75.155401.
Satta, M., Dipartimento di Fisica dell'Universita di Roma 'La Sapienza', Piazzale Aldo Moro 5, 00185 Rome, Iacobucci, S., & Larciprete, R.. Molecular adsorption and multilayer growth of pentacene on Cu(100): Layer structure and energetics. United States. doi:10.1103/PHYSREVB.75.155401.
Satta, M., Dipartimento di Fisica dell'Universita di Roma 'La Sapienza', Piazzale Aldo Moro 5, 00185 Rome, Iacobucci, S., and Larciprete, R.. Sun . "Molecular adsorption and multilayer growth of pentacene on Cu(100): Layer structure and energetics". United States. doi:10.1103/PHYSREVB.75.155401.
@article{osti_20957812,
title = {Molecular adsorption and multilayer growth of pentacene on Cu(100): Layer structure and energetics},
author = {Satta, M. and Dipartimento di Fisica dell'Universita di Roma 'La Sapienza', Piazzale Aldo Moro 5, 00185 Rome and Iacobucci, S. and Larciprete, R.},
abstractNote = {We used the partial charge tight binding method to perform a full structure optimization to determine equilibrium adsorption geometries, energetics, and local charge redistribution for molecular adsorption and multilayer growth of pentacene on Cu(100). We found that single molecule adsorption induces only a localized perturbation of the metal lattice which is limited to the topmost layers. At saturation coverage four stable topologies (Brick, Wave, Lines and Zigzag) were identified, all based on pentacene molecules lying flat on the metal surface and with the central phenyl ring adsorbed in top position. Only two (Brick and Wave) out of the four structures are able to sustain multilayer growth. In both cases, assembling beyond the second layer corresponds to a transition from the flat to a tilted geometry, in which the pentacenes adopt a face-plane-face arrangement leading to a herringbone structure. The energetics of the different structure are reported as a function of the molecular number density of the pentacene multilayer by calculating cohesive, stress, and electrostatic energies. The dominant tilted molecular orientation in the pentacene multilayer is in agreement with the average tilt angle of 65 deg. between the molecular plane and the Cu surface derived by near edge x-ray absorption spectroscopy of a four monolayer pentacene film deposited on Cu(100)},
doi = {10.1103/PHYSREVB.75.155401},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 15,
volume = 75,
place = {United States},
year = {Sun Apr 15 00:00:00 EDT 2007},
month = {Sun Apr 15 00:00:00 EDT 2007}
}
  • We report on the influence of defects in the electronic properties of a pentacene single-layer grown on a benzenethiolate self-assembled-monolayer (Bt-SAM) adsorbed on Cu(100) at 300 K, using high-resolution ultraviolet photoelectron spectroscopy. The weak interaction between pentacene and the underlying Bt-SAM is deduced by the lineshape and evolution of the highest-occupied molecular orbital (HOMO). Closer inspection of the pentacene HOMO band reveals a skewed feature, where the contribution in the low binding energy side is found originating from states associated to structural defects that can be reduced by controlled mild-temperature annealing (355 K). Presence of such defects influences also themore » pentacene HOMO onset energy and hole-injection barrier that can be reduced to typical value of this organic heterostructure after the annealing.« less
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  • One important issue for integrating atomic-layer-deposited (ALD) TaN barrier metal into Cu interconnects is a low thickness margin due to high electrical resistivity ({approx}50 m{omega} cm) of ALD-TaN. In investigating this issue, the median via resistance (0.16 {mu}m diameter vias) was found to increase from 0.5 to 26 {omega}/via as the ALD-TaN thickness was increased from 1 to 2 nm. To reduce the resistivity of ALD-TaN, its atomic concentration on various substrates was investigated. The N/Ta ratio of ALD-TaN was found to be about 4/5 on a SiO{sub 2} substrate but about 1/2 on a Ta substrate. We also confirmedmore » that the Ta-rich ALD-TaN film on the Ta substrate had low electrical resistivity ({approx}2 m{omega} cm). We could thus successfully obtain low via resistance (5.4 {omega}/via) with thick ALD-TaN (5 nm) by using a PVD-Ta/ALD-TaN/PVD-Ta multilayer structure.« less
  • The unambiguous identification of adsorption sites is demonstrated using absolute and relative polarization-dependent surface extended-x-ray-absorption fine-structure amplitude functions. This empirical procedure is generally applicable to all oriented adsorbates on single-crystal substrates.
  • The structure and orientation of adsorbed myoglobin as directed by metal-histidine complexation at the liquid-film interface was studied as a function of time using neutron and X-ray reflectivity (NR and XR, respectively). In this system, adsorption is due to the interaction between iminodiacetate (IDA)-chelated divalent metal ions Ni(II) and Cu(II) and histidine moieties at the outer surface of the protein. Adsorption was examined under conditions of constant area per lipid molecule at an initial pressure of 40 mN/m. Adsorption occurred over a time period of about 15 h, allowing detailed characterization of the layer structure throughout the process. The layermore » thickness and the in-plane averaged segment volume fraction were obtained at roughly 40 min intervals by NR. The binding constant of histidine with Cu(II)-IDA is known to be about four times greater than that of histidine with Ni(II)-IDA. The difference in interaction energy led to significant differences in the structure of the adsorbed layer. For Cu(II)-IDA, the thickness of the adsorbed layer at low protein coverage was {le} 20 {angstrom} and the thickness increased almost linearly with increasing coverage to 42 {angstrom}. For Ni(II)-IDA, the thickness at low coverage was - 38 {angstrom} and increased gradually with coverage to 47 {angstrom}. The in-plane averaged segment volume fraction of the adsorbed layer independently confirmed a thinner layer at low coverage for Cu(II)-IDA. These structural differences at the early stages are discussed in terms of either different preferred orientations for isolated chains in the two cases or more extensive conformational changes upon adsorption in the case of Cu(II)-IDA. Subphase dilution experiments provided additional insight, indicating that the adsorbed layer was not in equilibrium with the bulk solution even at low coverages for both IDA-chelated metal ions. We conclude that the weight of the evidence favors the interpretation based on more extensive conformational changes upon adsorption to Cu(II)-IDA.« less