Hybridisation at the organic–metal interface: a surface-scientific analogue of Hückel's rule?

Harutyunyan, Hasmik; Callsen, Martin; Allmers, T.; Caciuc, Vasile; Blügel, Stefan; Atodiresei, Nicolae; Wegner, Daniel

doi:10.1039/c3cc42574f

Cited by 15 publications

(24 citation statements)

References 17 publications

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“…However, when adsorbed on the surface considered here, the planar structure of the carbon atoms is approximately restored. This has previously been shown to occur when COT is chemisorbed onto a surface with the resulting strong hybridization between molecular and surface electronic states [48]. Similar to the Bz case, the hydrogen atoms are positioned in a plane higher than that of the carbons, in this case by approximately 0.11Å.…”

Section: Structuresmentioning

confidence: 70%

Atomic-scale inversion of spin polarization at an organic-antiferromagnetic interface

et al. 2013

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Using first-principles calculations, we show that the magnetic properties of a two-dimensional antiferromagnetic transition-metal surface are modified on the atomic scale by the adsorption of small organic molecules. We consider benzene (C6H6), cyclooctatetraene (C8H8) and a small transition metal -benzene complex (BzV) adsorbed on a single atomic layer of Mn deposited on the W(110) surface -a surface which exhibits a nearly antiferromagnetic alignment of the magnetic moments in adjacent Mn rows. Due to the spin-dependent hybridization of the molecular pz orbitals with the d states of the Mn monolayer there is a significant reduction of the magnetic moments in the Mn film. Furthermore, the spin-polarization at this organic-antiferromagnetic interface is found to be modulated on the atomic scale, both enhanced and inverted, as a result of the molecular adsorption. We show that this effect can be resolved by spin-polarized scanning tunneling microscopy (SP-STM). Our simulated SP-STM images display a spatially-dependent spin-resolved vacuum charge density above an adsorbed molecule -i.e., different regions above the molecule sustain different signs of spin polarization. While states with s and p symmetry dominate the vacuum charge density in the vicinity of the Fermi energy for the clean magnetic surface, we demonstrate that after a molecule is adsorbed those d-states, which are normally suppressed due to their symmetry, can play a crucial role in the vacuum due to their interaction with the molecular orbitals. We also model the effect of small deviations from perfect antiferromagnetic ordering, induced by the slight canting of magnetic moments due to the spin spiral ground state of Mn/W(110). PACS numbers:arXiv:1308.0934v2 [cond-mat.mtrl-sci]

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Section: Structuresmentioning

confidence: 70%

Atomic-scale inversion of spin polarization at an organic-antiferromagnetic interface

et al. 2013

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“…In these systems the injection barriers were found to be completely unpredictable from the substrate work function and molecular IE and EA, partly due to the appearance of a dipole Δ across the interface for any value of Φ (Figure c). Indeed, the Schottky‐Mott model fails to address the complex interactions that take place between an atomically clean metal and a molecular adsorbate: As described in section , as the molecule approaches the clean metal substrate, the respective electronic states may hybridize, causing the molecular orbitals to broaden and shift The bandgap of the organic semiconductor is affected by the polarizability of its surroundings: upon electron extraction from occupied levels or electron addition to unoccupied levels, the screening of this positive or negative charge by the surroundings tends to reduce the molecular bandgap .…”

Section: Energy Level Alignmentmentioning

confidence: 99%

“…These are therefore chemisorptive systems that operate under different mechanisms. Several recent studies have sought to elucidate the process of chemisorption between the molecule and the metal substrate . In many of these the XSW technique has proven to be an invaluable tool, since it is able to precisely determine the conformation of the adsorbed molecule, shedding light on which of the atoms are most closely involved in the chemical processes.…”

Section: Energy Level Alignmentmentioning

confidence: 99%

Multi‐Component Organic Layers on Metal Substrates

et al. 2015

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Increasingly high hopes are being placed on organic semiconductors for a variety of applications. Progress along these lines, however, requires the design and growth of increasingly complex systems with well-defined structural and electronic properties. These issues have been studied and reviewed extensively in single-component layers, but the focus is gradually shifting towards more complex and functional multi-component assemblies such as donor-acceptor networks. These blends show different properties from those of the corresponding single-component layers, and the understanding on how these properties depend on the different supramolecular environment of multi-component assemblies is crucial for the advancement of organic devices. Here, our understanding of two-dimensional multi-component layers on solid substrates is reviewed. Regarding the structure, the driving forces behind the self-assembly of these systems are described. Regarding the electronic properties, recent insights into how these are affected as the molecule's supramolecular environment changes are explained. Key information for the design and controlled growth of complex, functional multicomponent structures by self-assembly is summarized.

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“…For this we have to consider the possibility of strong physisorption (or even chemisorption). While weak physisorption only leads to a broadening of the MO levels (as described above), a strong molecule–substrate hybridization (i.e., strong physisorption or chemisorption) can lead to a strong broadening of a MO level as well as significant shifts in binding energy even to a degree that this state changes its occupancy due to charge transfer with the substrate [ 48 , 51 – 54 ]. For the SOMO scenario, we would expect the transfer of one electron from the Pt d z² state to the Au substrate, but the emergence of a Coulomb blockade would require that the MO is still well localized and should be clearly visible as peaks in STS spectra.…”

Section: Resultsmentioning

confidence: 99%

Spectroscopic mapping and selective electronic tuning of molecular orbitals in phosphorescent organometallic complexes – a new strategy for OLED materials

Ewen¹,

Sanning²,

Koch³

et al. 2014

Beilstein J. Nanotechnol.

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SummaryThe improvement of molecular electronic devices such as organic light-emitting diodes requires fundamental knowledge about the structural and electronic properties of the employed molecules as well as their interactions with neighboring molecules or interfaces. We show that highly resolved scanning tunneling microscopy (STM) and spectroscopy (STS) are powerful tools to correlate the electronic properties of phosphorescent complexes (i.e., triplet emitters) with their molecular structure as well as the local environment around a single molecule. We used spectroscopic mapping to visualize several occupied and unoccupied molecular frontier orbitals of Pt(II) complexes adsorbed on Au(111). The analysis showed that the molecules exhibit a peculiar localized strong hybridization that leads to partial depopulation of a dz² orbital, while the ligand orbitals are almost unchanged. We further found that substitution of functional groups at well-defined positions can alter specific molecular orbitals without influencing the others. The results open a path toward the tailored design of electronic and optical properties of triplet emitters by smart ligand substitution, which may improve the performance of future OLED devices.

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Hybridisation at the organic–metal interface: a surface-scientific analogue of Hückel's rule?

Cited by 15 publications

References 17 publications

Atomic-scale inversion of spin polarization at an organic-antiferromagnetic interface

Atomic-scale inversion of spin polarization at an organic-antiferromagnetic interface

Multi‐Component Organic Layers on Metal Substrates

Spectroscopic mapping and selective electronic tuning of molecular orbitals in phosphorescent organometallic complexes – a new strategy for OLED materials

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