Electron-Vibron Coupling in High-Resolution X-Ray Absorption Spectra of Organic Materials: NTCDA on Ag(111)

Schöll, A.; Zou, Ying; Kilian, L.; Hübner, D.; Gador, D.; Jung, Ch.; Urquhart, Stephen G.; Schmidt, Thomas; Fink, R.; Umbach, E.

doi:10.1103/physrevlett.93.146406

Cited by 46 publications

(44 citation statements)

References 19 publications

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“…NEXAFS spectra of the same material deposited from different solvents and processing conditions are substantially different. This indicates a far more extensive breakdown of the "building-block" picture than previously reported, [4,5] allowing p-interactions to be studied. The surface sensitivity has recently been established to be ca.…”

mentioning

confidence: 84%

Solvent Effects on Chain Orientation and Interchain π‐Interaction in Conjugated Polymer Thin Films: Direct Measurements of the Air and Substrate Interfaces by Near‐Edge X‐ray Absorption Spectroscopy

Chua

Dipankar

et al. 2007

Advanced Materials

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The orientation and packing of semiconducting polymer chains at film interfaces crucially affects charge injection and transport at those interfaces. Although X-ray diffraction techniques have been used extensively as a structural probe, they are not particularly sensitive to these interfaces. Near-edge X-ray absorption fine-structure spectroscopy (NEXAFS), on the other hand, is sensitive to surface orientation and has been applied to investigate polymer structures, for example, in polyimide, [1] polyfluorene, [2] and polythiophene.[3] Here we show that NEXAFS band shapes and intensities are in fact also sensitive to the intermolecular p-interaction in regioregular poly(3-hexylthiophene) (rreg-P3HT) films. NEXAFS spectra of the same material deposited from different solvents and processing conditions are substantially different. This indicates a far more extensive breakdown of the "building-block" picture than previously reported, [4,5] allowing p-interactions to be studied. The surface sensitivity has recently been established to be ca. 2.5 nm for the total electron yield in rreg-P3HT, [6] which is highly relevant to interfacial charge transport and surface-induced self-organization. Rreg-P3HT thin films were deposited from a wide range of solvent qualities, and both the air and substrate interfaces were studied. Delamination was used to expose the substrate interface. We found that: i) the thiophene (Th)-ring orientation at both these interfaces was disordered and showed only a weak preference for the out-of-plane (oop) stacking favorable for field-effect mobility (l FET ); ii) the hexyl side chains were also disordered; and iii) the interchain p-interaction was strongly dependent on the deposition solvent quality, and varied in opposite directions between the air and substrate interfaces, being generally better at the substrate than the air interface. Direct imaging by friction-mode atomic force microscopy (AFM) revealed the expected presence of a mosaic surface morphology with a finer length scale than surface topography. Transistor l FET measurements suggested that the high l FET of rreg-P3HT is still limited by heterogeneity, which we attribute to the distribution of interface domains of varying orientation and/or packing. This ability to directly measure chain segmental orientation and interaction at the interfaces will open the way to their systematic optimization for even higher device performance.The self-organization behavior of polymers at interfaces is of significant scientific and technological interest. Much of the structural knowledge of conjugated polymers such as rreg-P3HT, a prototype high-l FET polymer, has come from wideangle [7,8] and grazing-angle X-ray diffraction (GIXRD) [9,10] studies. For polythiophenes, the chains p-stack to give short interchain distances (3.8 Å in rreg-P3HT) in the lamellae plane, but long distances (17 Å in rreg-P3HT) between lamellae separated by the alkyl side chains. [7][8][9][10] These p stacks further show a preference for either oop stacking in which the plane...

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confidence: 84%

Solvent Effects on Chain Orientation and Interchain π‐Interaction in Conjugated Polymer Thin Films: Direct Measurements of the Air and Substrate Interfaces by Near‐Edge X‐ray Absorption Spectroscopy

Chua

Dipankar

et al. 2007

Advanced Materials

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“…One saturated NTCDA monolayer was obtained by depositing a thick film followed by subsequent desorption of the multilayers upon a mere annealing at about 385 K. At this temperature, only the first molecular layer remains stuck to the metal due to the strong bonding between NTCDA and the Ag(1 1 1) at the interface [13].…”

Section: Methodsmentioning

confidence: 99%

“…As shown earlier in Refs. [13,31] the absorption resonances marked by A and B in the CIS spectra are assigned to the excitations of C1s electrons of the naphthalene core into different unoccupied molecular orbitals, whereas resonances C and D are attributed to the excitations of the carbon atoms of the anhydride groups. This finding has been corroborated by a straightforward comparison with the NEXAFS spectra of naphthalene-dicarbonic acid anhydride (NDCA) on Ni(1 1 1), where the NDCA molecule consists of naphthalene core attached with only one anhydride group [32] and by calculations [13].…”

Section: ML Ntcda/ag(1 1 1) -Spectroscopy At the Carbon K-edgementioning

confidence: 99%

“…The NTCDA/Ag(1 1 1) system has already been studied by other techniques, in particular by low energy electron diffraction (LEED) [8,9], scanning tunneling microscopy (STM) [9], normal incidence X-ray standing waves (NIXSW) [10], X-ray photoelectron spectroscopy (XPS) and near-edge X-ray adsorption fine structure (NEXAFS) [11][12][13][14]. To summarize briefly, NTCDA is a semiconductor molecule with the chemical formula of C 14 functional groups.…”

Section: Introductionmentioning

confidence: 99%

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Electronic structure of 1ML NTCDA/Ag(111) studied by photoemission spectroscopy

et al. 2007

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“…Most investigations so far focused on the chemistry and physics of thin films deposited on surfaces. In a number of experiments NTCDA was deposited on a Ag(1,1,1) surface and investigated by X-ray absorption and photoemission [4][5][6][7]. Thin films on a Au substrate were also studied by photoelectron spectroscopy and an IE of 8 eV was reported [8].…”

Section: Introductionmentioning

confidence: 99%

Threshold Photoelectron Spectrum of Isolated NTCDA

Fischer

Fischer²,

Bodi

2011

Zeitschrift Für Physikalische Chemie

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The threshold photoelectron spectrum of NTCDA (1,4,5,8-naphthalene-tetracarboxylic dianhydride) has been recorded using synchrotron radiation. An ionization energy of 9.66 eV was observed. The experiments are supported by DFT computations that yield a value of 9.51 eV, in good agreement with the measured value. Several bands corresponding to excited electronic states of the cation are also visible and can be assigned with the aid of computations.

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Electron-Vibron Coupling in High-Resolution X-Ray Absorption Spectra of Organic Materials: NTCDA on Ag(111)

Cited by 46 publications

References 19 publications

Solvent Effects on Chain Orientation and Interchain π‐Interaction in Conjugated Polymer Thin Films: Direct Measurements of the Air and Substrate Interfaces by Near‐Edge X‐ray Absorption Spectroscopy

Solvent Effects on Chain Orientation and Interchain π‐Interaction in Conjugated Polymer Thin Films: Direct Measurements of the Air and Substrate Interfaces by Near‐Edge X‐ray Absorption Spectroscopy

Electronic structure of 1ML NTCDA/Ag(111) studied by photoemission spectroscopy

Threshold Photoelectron Spectrum of Isolated NTCDA

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