Highest-Occupied-Molecular-Orbital Band Dispersion of Rubrene Single Crystals as Observed by Angle-Resolved Ultraviolet Photoelectron Spectroscopy

Machida, Shin’ichi; Nakayama, Yasuo; Duhm, Steffen; Xin, Qian; Funakoshi, Akihiro; Ogawa, Naoki; Kera, Satoshi; Ueno, Nobuo; Ishii, Hisao

doi:10.1103/physrevlett.104.156401

Cited by 194 publications

(200 citation statements)

References 40 publications

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“…Therefore, the molecular arrangement is crucial for all of the proposed models ranging from the incoherent hopping to the coherent band-like transport models, which are still under debate. Experimentally, band dispersion measurements by means of photoelectron spectroscopy have been performed on thin films to prevent the charge-up problem [19][20][21] , and the reports on singlecrystal samples are limited 22,23 . The theoretical studies on the transport properties reported thus far have been based on bulk single crystals [24][25][26][27][28][29] .…”

Section: Resultsmentioning

confidence: 99%

Large surface relaxation in the organic semiconductor tetracene

et al. 2014

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Organic crystals are likely to have a large degree of structural relaxation near their surfaces because of the weak inter-molecular interactions. The design of organic field-effect transistors requires a detailed knowledge of the surface relaxation as the carriers usually transfer within the first few molecular layers at the semiconductor surfaces, and their transport properties reflect the structural changes through the transfer integral. Here, we report the direct observation of the surface relaxation of an organic semiconductor, a tetracene single crystal, by means of X-ray crystal truncation rod scattering measurements. A significant degree of surface relaxation is observed, taking place only in the first monolayer at the semiconductor surface. First principles calculations show that the resultant transfer integrals are completely different between the bulk and surface of the semiconductor.

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Section: Resultsmentioning

confidence: 99%

Large surface relaxation in the organic semiconductor tetracene

et al. 2014

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“…In contrast to vacuumsublimated thin films, however, organic SCs commonly exhibit serious charging upon ionizing UV irradiation or electron bombardment, which hinders ultraviolet photoelectron spectroscopy (UPS) or low-energy electron diffraction (LEED) investigations to probe the band structure and the crystal orientation. It was demonstrated for UPS that the charging can be overcome by concomitant illumination by UV and laser light [1][2][3], and recently some of the present authors and coworkers succeeded in measuring the band dispersion of rubrene SCs at room temperature by angle-resolved UPS (ARUPS) [4]. However, to our knowledge, no LEED study of an organic SC exists so far, although LEED is a straightforward approach to access the surface Brillouin zone and thus the orientation of a SC.…”

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confidence: 96%

Accessing Surface Brillouin Zone and Band Structure of Picene Single Crystals

et al. 2012

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We have experimentally revealed the band structure and the surface Brillouin zone of insulating picene single crystals (SCs), the mother organic system for a recently discovered aromatic superconductor, with ultraviolet photoelectron spectroscopy (UPS) and low-energy electron diffraction with laser for photoconduction. A hole effective mass of 2.24 m0 and the hole mobility µ h ≥ 9.0 cm 2 /Vs (298 K) were deduced in Γ-Y direction. We have further shown that some picene SCs did not show charging during UPS even without the laser, which indicates that pristine UPS works for high-quality organic SCs.

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“…Several experimental and theoretical publications address the formation of Bloch-like states in organic materials, but a significant band dispersion is only observed for aromatic condensates with extended p-systems. There, the band width can be of the order of some 100 meV along the p-stacks [7][8][9][10][11][12][13][14][15] , while it is much smaller in other directions 9,16 . It is moreover well-established that the bonding to a metal substrate can lead to new states at the interface because of hybridization between metal and molecular wave functions 17,18 .…”

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Substrate-mediated band-dispersion of adsorbate molecular states

et al. 2013

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Charge carrier mobilities in molecular condensates are usually small, as the coherent transport, which is highly effective in conventional semiconductors, is impeded by disorder and the small intermolecular coupling. A significant band dispersion can usually only be observed in exceptional cases such as for p-stacking of aromatic molecules in organic single crystals. Here based on angular resolved photoemission, we demonstrate on the example of planar p-conjugated molecules that the hybridization with a metal substrate can substantially increase the delocalization of the molecular states in selective directions along the surface. Supported by ab initio calculations we show how this mechanism couples the individual molecules within the organic layer resulting in an enhancement of the in-plane charge carrier mobility.

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Highest-Occupied-Molecular-Orbital Band Dispersion of Rubrene Single Crystals as Observed by Angle-Resolved Ultraviolet Photoelectron Spectroscopy

Cited by 194 publications

References 40 publications

Large surface relaxation in the organic semiconductor tetracene

Large surface relaxation in the organic semiconductor tetracene

Accessing Surface Brillouin Zone and Band Structure of Picene Single Crystals

Substrate-mediated band-dispersion of adsorbate molecular states

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