X‐ray determination of the crystal structure and orientation of vacuum evaporated sexithiophene films

Servet, Bernard; Ries, Simone; Trotel, Marie; Alnot, P.; Horowitz, Gilles; Garnier, F.

doi:10.1002/adma.19930050611

Cited by 140 publications

(103 citation statements)

References 11 publications

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“…The 6T exposures were monitored by a water cooled quartz microbalance and are given in terms of nominal thickness given the 6T density of 1.55 g/cm 3 (Refs. [13][14][15]). The typical 6T growth rates used were 1.5 ± 0.5 Å /min.…”

Section: Methodsmentioning

confidence: 97%

Sexithiophene films on ordered and disordered TiO2(110) surfaces: Electronic, structural and morphological properties

et al. 2007

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Section: Methodsmentioning

confidence: 97%

Sexithiophene films on ordered and disordered TiO2(110) surfaces: Electronic, structural and morphological properties

et al. 2007

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“…Therefore, it is important to understand and control the kinetics of growth in order to infer the basic relations between film structure, molecular ordering, and the relevant electri-164 6 Electronic Structure and Energy Transfer in Solid a-Sexithienyl cal and optical properties, as well as to obtain films of reproducible quality. It was found by X-ray diffraction (XRD) that T 6 films grown at room deposition temperature (RT) possess long-range molecular order [3,36,37] and therefore there is a spontaneous tendency towards ordered aggregation. Upon changes of the deposition temperature, enhanced anisotropy in the electrical properties was observed, as correlated to structural (XRD) and morphological (SEM) changes [38].…”

Section: Growth In High Vacuummentioning

confidence: 99%

Electronic Structure and Energy Transfer in Solid α‐Sexithienyl

Taliani¹,

Biscarini²,

Muccini³

1999

Semiconducting Polymers

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Semiconducting conjugated polymers have been widely studied over the last twenty years for their unique electronic and optical properties, which fundamentally reside on the delocalized p-electron structure. In the early stages of the study of conjugated polymers it was thought that the p-conjugated backbone would provide the pathway for coherent electronic transport within the macromolecular unit. Further studies showed, however, that real polymers have a finite distribution of conjugated chain lengths and it became clear that electron transport would ultimately be limited by interchain hopping. Other trapping centers for electron transport are chemical defects of the macromolecular ensemble as well as morphological disorder of the material. It was at this stage that the use of oligomers had the first impulse and was widely considered a valuable route to the understanding of the intrinsic properties of conjugated polymers. In the early nineties the development of organic field effect transistors (FET), based on a-sexithienyl (T 6 ) by Garnier et al. [1,2] and confirmed soon after by Ostoja et al. [3] and Dodabalapur et al. [4], clearly indicated that the availability of chemically pure and ordered solids was the requisite to achieve reasonable working conditions for the FET operation. This finding opened the avenue for the development of the so-called plastic electronics. Disorder moreover is detrimental not only to electric transport but also, to a lesser extent, energy transport. Both charge and energy transport are among the basic steps in the operation of the organic light emitting diodes (OLED) [5,6]. Recombination is followed by energy transfer within the manifold of the excited electronic states leading ultimately to an exciton. The notion of excitons as lowest excitations in conjugated solids is now universally accepted since the emission of OLED is molecular in character as opposed to band-to-band radiative electron-hole recombination. Excitons in molecular crystals were extensively studied over the last decades [7,8]. Anisotropic intermolecular interactions in the ordered molecular solids were shown to allow the formation of collective Bloch electronic excitations (Frenkel excitons) in which the excitation is strongly bound to the molecular entity and therefore is called tight bound exciton as opposed to the weakly bound exciton (Wannier exciton) in inorganic semiconductors. Nevertheless, the excitonic band structure of conjugated oligomers is not known and the relative energy of the lowest singlet Semiconducting Polymers: Chemistry, Physics and Engineering. Edited by G. Hadziioannou and P. F. van Hutten

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“…33 However, the natural direction of growth of the bulk molecular crystal was still found to dominate the molecular aggregation from the very first layer, that is, standing-up orientation for sexiphenyl and lying-down orientation for sexithiophene (because this orientation is characteristic of the 6T bulk polymorphs 34 and thin films 35 ). Here we show the formation of a compact monolayer of lyingdown pentacene on the unreconstructed and stoichiometric TiO 2 (110) surface.…”

mentioning

confidence: 99%

Planar Growth of Pentacene on the Dielectric TiO₂(110) Surface

Lanzilotto

Sánchez‐Sánchez

Bavdek³

et al. 2011

J. Phys. Chem. C

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We have studied the growth of pentacene molecules on the unreconstructed and stoichiometric surface of TiO2(110). At variance with its characteristic homeotropic growth mode, pentacene is found to be physisorbed on this dielectric substrate with its long molecular axis oriented parallel to the surface and aligned along the [001] direction. Pentacene molecules couple side-by-side into long stripes running along the [11̅0] direction, where the overlayer preserves the substrate lattice periodicity (∼6.5 Å). In the opposite direction, head-to-head pentacene repulsion drives the ordering of the stripes, whose spacing simply depends on the surface coverage. By near-edge X-ray absorption, NEXAFS, we have determined the pentacene molecules to be tilted by ∼25° off the surface around their long axis. At the monolayer coverage, the pentacene orientation and spacing are very close to that of the (010) bulk planes (also called a−c planes) of pentacene crystals. We have observed that at least two additional layers can be grown on top of the monolayer following a planar configuration. Both the strong side-by-side intermolecular attraction and the full development of the bulklike electronic states, as probed by NEXAFS, suggest an optimal charge transport along the monolayer stripes of lying-down molecules.

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X‐ray determination of the crystal structure and orientation of vacuum evaporated sexithiophene films

Cited by 140 publications

References 11 publications

Sexithiophene films on ordered and disordered TiO2(110) surfaces: Electronic, structural and morphological properties

Sexithiophene films on ordered and disordered TiO2(110) surfaces: Electronic, structural and morphological properties

Electronic Structure and Energy Transfer in Solid α‐Sexithienyl

Planar Growth of Pentacene on the Dielectric TiO₂(110) Surface

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X‐ray determination of the crystal structure and orientation of vacuum evaporated sexithiophene films

Cited by 140 publications

References 11 publications

Sexithiophene films on ordered and disordered TiO2(110) surfaces: Electronic, structural and morphological properties

Sexithiophene films on ordered and disordered TiO2(110) surfaces: Electronic, structural and morphological properties

Electronic Structure and Energy Transfer in Solid α‐Sexithienyl

Planar Growth of Pentacene on the Dielectric TiO2(110) Surface

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Planar Growth of Pentacene on the Dielectric TiO₂(110) Surface