Site-Specific Polarization Screening in Organic Thin Films

Soubatch, Serguei; Weiss, Christian; Temirov, Ruslan; Tautz, F. Stefan

doi:10.1103/physrevlett.102.177405

Cited by 29 publications

(37 citation statements)

References 25 publications

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“…A careful analysis of the electronic spectra, recorded with STS, confirms this conjecture, as the discussion in Ref. 35 shows. In short because of strong shifts in the energy position of the LUMO level due to site-specific polarization screening, it is possible at bias voltages below 1.8 V to image the lower (i.e., interface) layer of the β-phase through the band gap of the molecules in the upper (i.e., surface) layer, while above 1.8.…”

Section: A Preparation Of the β-Phasesupporting

confidence: 69%

“…Such a tilt has already been predicted by Langner et al, 1 but we can exclude one of their proposed models, namely the symmetric tilt of both molecules, since we observe these molecules to be nonequivalent in STM. Based on our STS data, 35 we can conclude that the tilt of B molecules is larger than that of the A molecules, because the LUMO of A molecules is found closer to the Fermi level and is broadened more strongly; this reveals a stronger electronic coupling to the metal and hence a smaller tilt angle, if any.…”

Section: Structure Model For the β-Phasementioning

confidence: 72%

“…It is marked with C (here and later the notation is the same as in Ref. 35). Its contrast is similar to the submolecular structure of molecules in the α-phase, i.e., four narrow lobes that are oriented perpendicular to the long molecular axis in the center of the molecule and two more circular features at either end of the molecule.…”

Section: A Preparation Of the β-Phasementioning

confidence: 99%

“…It has been shown in Ref. 35 that chains may consist of monomers (D molecule) or dimers (E and D molecules), dimers being the more frequent case [cf. Fig.…”

Section: Structure Model For the β-Phasementioning

confidence: 99%

“…1 Yet the available experimental data on this interface is limited. 1,10,[33][34][35] The emphasis in the present study is placed on structural data collected with scanning tunneling microscopy (STM) and low energy electron diffraction (LEED); in particular we present a refined phase diagram of the Tc/Ag(111) interface in the coverage range 0 to 2.4 MLs. Based on the structural data presented here, electronic structure studies, 35 kinetic growth studies, etc., may be performed in the future.…”

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confidence: 99%

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Structure and growth of tetracene on Ag(111)

et al. 2011

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The structure of the tetracene/Ag(111) interface in the coverage range θ = 0 to 2.4 ML is studied with scanning tunneling microscopy (STM) at 8 K and with low energy electron diffraction (LEED) at T = 300 . . . 100 K. For θ 0.01 ML, one-dimensional (1D) diffusion of single molecules along 011 -directions is observed even at 8 K. For 0.1 ML < θ < 0.5 ML molecules are homogeneously distributed over the surface forming a disordered phase (static at T = 8 K, dynamic at T = 25 K), indicating a repulsive intermolecular interaction (δ-phase). For θ 0.5 ML, local ordering in the commensurate γ -phase is observed. Further increase of the coverage yields a compressed monolayer (ML) phase (θ ≡ 1 ML) with point-on-line registry (α-phase). The interaction between molecules has been calculated with the force-field approach to rationalize the molecular packing motifs in the various phases. Under most circumstances molecule-molecule interactions are repulsive, in agreement with experimental findings. A simulation of the adsorption up to θ = 1 ML according to the random sequential adsorption (RSA) algorithm shows that the disorder-to-order transition from the δ-to γ -phase occurs close to random close packing (RCP), θ = 0.5-0.6 ML. Since tetracene molecules are a two-dimensional (2D) representation of Onsager's hard rod model, this suggests that this phase transition is driven both energetically and entropically. For θ ≈ 2.23 ML a metastable bilayer phase with point-on-line coincidence is observed (β-phase). The basic structural unit of this phase is a triplet of molecules that are tilted along the long molecular axis against each other; at least one of these molecules is tilted out of the surface plane. Within the β-phase a superstructure of alternating rotation domains is observed. This superstructure has a period of 7.4 nm. The molecular packing in the β-phase resembles the packing in the bulk crystal structure of tetracene, its formation can therefore be interpreted as incipient pseudomorphic growth of tetracene on Ag(111). However, pseudomorphic growth cannot be continued beyond the β-phase.

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Section: A Preparation Of the β-Phasesupporting

confidence: 69%

Section: Structure Model For the β-Phasementioning

confidence: 72%

Section: A Preparation Of the β-Phasementioning

confidence: 99%

“…It has been shown in Ref. 35 that chains may consist of monomers (D molecule) or dimers (E and D molecules), dimers being the more frequent case [cf. Fig.…”

Section: Structure Model For the β-Phasementioning

confidence: 99%

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confidence: 99%

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Structure and growth of tetracene on Ag(111)

et al. 2011

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Molecular Organic Films

Sokołowski¹

2014

Surface and Interface Science

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Effect of Aromatic Solvents Residuals on Electron Mobility of Organic Single Crystals

Xue

Peng

et al. 2022

Adv Elect Materials

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Ideally, balanced transport for both hole and electron carriers is favored in these double-carrier devices. But in actual, there is still a big lag between the electron and hole transport properties. For instance, the extremely high hole mobility has reached much more than 20 cm 2 V −1 s −1 , [10][11][12][13][14] but in sharp contrast, very few literatures have reported electron mobility beyond 10 cm 2 V −1 s −1 . [15][16][17][18][19] Understanding the determining factors that limit the charge mobility, especially for electron transport, is significant yet challenging. Several typical obstacles to electron conductance, such as the high electron injection barriers [20][21][22] and the electron traps at the semiconductor-dielectric interface, [23] have been widely studied. The polarity of dielectric layer, consisting of a set of dipoles, [24] has another crucial effect. In 2003, Veres et al. observed that charge transport showed strong correlation with dielectric polarizability and they put forward that the dielectric layer could change the density of states by local polarization effects and thus affect the charge transport and indeed, carrier localization is enhanced by insulators with larger permittivity. [22,25] The dominant mechanism is the so-called dipolar disorder. [25][26][27][28] Hulea et al. carried on measurements on rubrene single-crystal devices for the observation of intrinsic charge-transport characteristics and reported that the mobility dependence on dielectric polarizability has a dynamic origin owing to the coupling of the charged carriers in the organic conducting channel to the ionic lattice of the dielectric. [29] This coupled carrier-polarization cloud is referred to as a "Fröhlich polaron" [30][31][32] and moves with electron (or hole). The authors also demonstrated that the charge mobility would switch from a band-like character to a hopping one when the dielectric polarizability increased. In addition to the polarity of dielectrics, we further found that the polarity effects could arise from the solvent residues in solution-processed organic semiconductors. In fact, the existence of polar solvent residues is identified as a factor detrimental to electron transport. [15,33] Both of 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene), and an n-type material, 6,13-bis(triisopropyl silylethynyl)-5,7,12,14-tetraazapentacene (TIPS-TAP), have been examined. Crystals of TIPS-pentacene grown from non-polar solvents exhibited ambipolar transport for the first time with Balanced electron and hole transport properties are essential for various organic electrical/optoelectrical applications such as organic solar cells, complementary circuits, and light-emitting transistors. However, the electron transport in organic semiconductor lags far behind the hole side, making it with vital significance to seek the factors that limit the electron mobility. Here, the authors demonstrate that the π-conjugated solvents, as essential components in the widely-used solution processing techniques, can signific...

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Site-Specific Polarization Screening in Organic Thin Films

Cited by 29 publications

References 25 publications

Structure and growth of tetracene on Ag(111)

Structure and growth of tetracene on Ag(111)

Molecular Organic Films

Effect of Aromatic Solvents Residuals on Electron Mobility of Organic Single Crystals

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