Structural properties of tetracene films on Ag(111) investigated by SPA-LEED and TPD

Langner, Andreas; Hauschild, A.; Fahrenholz, Sonja; Sokołowski, M.

doi:10.1016/j.susc.2004.10.031

Cited by 51 publications

(91 citation statements)

References 42 publications

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“…1). The structure of the phase as derived from our STM images (flat-lying molecules, unit cell vectors b 1 ¼ 8:2 A, b 2 ¼ 13:1 A, ¼ 93 ) agrees with the diffraction study reported previously [18]. The intramolecular contrast at positive bias voltages [ Fig.…”

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Site-Specific Polarization Screening in Organic Thin Films

et al. 2009

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Systematic local spectroscopy of the affinity levels, by means of a scanning tunneling microscope, in highly ordered molecular semiconductor films of tetracene reveals strong energy level shifts by up to $1:0 eV from molecule to molecule. This final state effect can be traced back to the site specificity of the polarization energy in organic materials with complex unit cells, caused by a combination of different molecular environments, the intrinsically anisotropic molecular polarizability, and the influence of the substrate.

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“…It was evaporated from an effusion cell at 420 K onto the silver surface at 210 K, where-depending on the preparation procedure-it may form two long-range ordered phases ( and ) [18]. At a nominal coverage of two monolayers (calibrated with respect to the compact -phase monolayer [18]) regions of both and phases coexist on the surface (Fig. 1).…”

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Site-Specific Polarization Screening in Organic Thin Films

et al. 2009

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“…With applications of organic semiconductors in organic (opto-)electronics in mind, the growth of organic semiconductors on various inorganic substrates has been studied in recent years. [1][2][3][4][5][6][7][8] In these studies it has turned out that often the growth of organic semiconductor films exhibits certain features that are not found in inorganic epitaxy (e.g., Refs. 1,2,8, and 9).…”

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“…Common adsorption energies are therefore below 1 eV per molecule. 1,10,11 The weak and unspecific molecule-substrate interaction implies low diffusion and incorporation barriers and thus will affect the growth kinetics of organic semiconductor films on metals. The interaction between the molecules is also nonchemical, giving rise to considerable structural flexibility of the growing film.…”

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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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“…The presence of the H atoms at the molecular borders and their morphology reduce the possibility of hybridization with metal states. Different ordered phases are found for Tc and Pn adsorption on noble metals Pn/Au(111) ) (Schroder2003), Pn/Au(110) (Floreano2006, Badvek2008), Pn/Au(111) (Kafer 2007a, Pn/Ag(111), (Danişman 2005, Eremtchenko 2005, Tc/Ag(111) (Langner et al 2005) and in some cases the phase diagram appears complex.…”

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confidence: 99%