Molecules on Insulating Films: Scanning-Tunneling Microscopy Imaging of Individual Molecular Orbitals

Repp, Jascha; Meyer, Gerhard; Stojkovic, Sladjana; Gourdon, André; Joachim, Christian

doi:10.1103/physrevlett.94.026803

Cited by 812 publications

(906 citation statements)

References 25 publications

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“…2e,f). These features show a molecular orbital-like electronic density and a periodicity of about 2.4 Å between bright lobes 28 . This distance corresponds to the lattice constant of graphene, indicating that these structures consist of a concatenation of benzene rings (see Supplementary Note 2 and Supplementary Figs 1 and 2).…”

Section: Resultsmentioning

confidence: 99%

Graphene etching on SiC grains as a path to interstellar polycyclic aromatic hydrocarbons formation

et al. 2014

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Polycyclic aromatic hydrocarbons as well as other organic molecules appear among the most abundant observed species in interstellar space and are key molecules to understanding the prebiotic roots of life. However, their existence and abundance in space remain a puzzle. Here we present a new top-down route to form polycyclic aromatic hydrocarbons in large quantities in space. We show that aromatic species can be efficiently formed on the graphitized surface of the abundant silicon carbide stardust on exposure to atomic hydrogen under pressure and temperature conditions analogous to those of the interstellar medium. To this aim, we mimic the circumstellar environment using ultra-high vacuum chambers and investigate the SiC surface by in situ advanced characterization techniques combined with first-principles molecular dynamics calculations. These results suggest that top-down routes are crucial to astrochemistry to explain the abundance of organic species and to uncover the origin of unidentified infrared emission features from advanced observations.

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Section: Resultsmentioning

confidence: 99%

Graphene etching on SiC grains as a path to interstellar polycyclic aromatic hydrocarbons formation

et al. 2014

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“…Franke et al have recently reduced the electronic coupling of C 60 with a metal surface by locking and lifting each fullerene with a second molecular species [7]. Furthermore, it has been shown that, upon adsorption of molecules on ultrathin NaCl films on metal surfaces, inherent electronic and optical properties of individual molecules can be studied [8][9][10]. However, to our knowledge, there are only three published STM studies on the growth of two-dimensional molecular islands on insulating NaCl layers, two of them on metal-containing porphyrine molecules [11,12], and the third one on C 60 molecules [13].…”

Section: Introductionmentioning

confidence: 99%

Stabilization of bimolecular islands on ultrathin NaCl films by a vicinal substrate

et al. 2009

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a b s t r a c tThe structure of ultrathin NaCl films on Au(1 1 1) and on Au(11 12 12), as well as the one of bimolecular 3,4,9,10-perylenetetracarboxylic diimide (PTCDI) and 1,4-bis-(2,4-diamino-1,3,5,-triazine)-benzene (BDATB) islands on NaCl films on both surfaces have been studied with a low-temperature scanning tunnelling microscope. We show that intermixed bimolecular assemblies based on selective three-fold hydrogen-bonding (H-bonding), that have previously been observed on Au(1 1 1) and on Au(11 12 12), can also be stabilized on insulating NaCl films on Au, however, only if these films are grown on Au(11 12 12) and not on Au(1 1 1). The behaviour of the heterocomplex structures is found to be largely influenced by the structural properties of the underlying substrate and by the number of NaCl layers. On a partly NaCl-covered Au(1 1 1) surface, the excess of molecules after completion of the first layer on Au prefers to form a second molecular layer based on ordered heterocomplex structures rather than to adsorb on the NaCl islands. The use of a vicinal surface together with the strong cohesion characteristic of the NaCl film introduces smooth elastic deformations on the NaCl(0 0 1) plane. As a consequence, the periodically modified structure of the overlayer provides preferential binding sites and allows adsorption of two-dimensional molecular structures. In contrast to what is observed on Au(11 12 12), the molecular domains on the NaCl film do not follow the Au step directions, but the NaCl(0 0 1) high symmetry directions. Our results provide a strategy to increase the adsorption energy of flat molecules on insulating layers by choosing a vicinal metal substrate.

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“…[19,34,38] The large lateral separation of the highly reactive Si "up" atoms on the silicene surface may be key to minimizing the hybridization between the Pc ligands and the silicene surface, in contrast to the case of other π-conjugated organic molecules on conventional Si surfaces. [16,18] Therefore, despite the small variation in binding configuration, which suggests the molecule is strongly pinned, the molecule retains localized states that resemble the states of the isolated molecule.…”

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confidence: 99%

Guided Molecular Assembly on a Locally Reactive 2D Material

et al. 2017

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occurs when 2D materials are placed on a substrate, such as when they are epitaxially grown upon a metallic surface. [11,12] For example, it has been shown that molecules can become trapped within nanopores of hexagonal boron nitride grown on Ru (0001) because of dipolar interactions; [13,14] similar results have also been observed for nanopores on the surface of bulk SiC. [15] Physisorption of a molecule to a surface (i.e., van der Waals bonding) is often not strong enough to fix the molecule's position at room temperature, particularly on the surface of bulk metal crystals. This is more readily accomplished by anchoring the mole cule to the surface through chemisorption of part of the molecule to the surface. [16][17][18] However, care must be taken to limit hybridization that can cause detrimental modifications of the molecule and its frontier orbitals, [19,20] especially on different surface reconstructions of bulk semiconductors like silicon. [15,17] It is therefore of interest to investigate the interface between molecules and more reactive 2D materials in an attempt to isolate individual molecules at room temperature while retaining their localized electronic states.With its mixed sp 2 -sp 3 character, silicene-the silicon analogue of graphene-has the potential to provide unique properties for molecular templating. This is particularly true because the structural and electronic properties of silicene are more susceptible to modification [21][22][23][24][25][26] once it is formed upon a surface, owing to its greater reactivity than graphene and the flexibility of The interactions between atomic or molecular adsorbates and the surfaces of 2D materials are of interest for applications ranging from catalysis [1] and molecular sensing [2] to molecular electronics and spintronics. [3][4][5] For the prototypical 2D material graphene, there are typically only weak van der Waals interactions between molecules and the surface. [6] This allows for the fabrication of functional self-assembled monolayers [6][7][8] that are reminiscent of the ordered supramolecular arrangements that can be formed on the surfaces of bulk (3D) materials. [9] However, isolating individual molecules is more challenging. [10] In contrast, new possibilities for templating emerge from nanostructuring that

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Molecules on Insulating Films: Scanning-Tunneling Microscopy Imaging of Individual Molecular Orbitals

Cited by 812 publications

References 25 publications

Graphene etching on SiC grains as a path to interstellar polycyclic aromatic hydrocarbons formation

Graphene etching on SiC grains as a path to interstellar polycyclic aromatic hydrocarbons formation

Stabilization of bimolecular islands on ultrathin NaCl films by a vicinal substrate

Guided Molecular Assembly on a Locally Reactive 2D Material

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