<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">C</mml:mi></mml:mrow><mml:mrow><mml:mn>60</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>bonding and energy-level alignment on metal and semiconductor surfaces

Ohno, Toshinobu; Chen, Y.; Harvey, S. E.; Kroll, G. H.; Weaver, J. H.; Haufler, R. E.; Smalley, R. E.

doi:10.1103/physrevb.44.13747

Cited by 324 publications

(128 citation statements)

References 43 publications

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“…The peak that appears at 1.9 eV has been identified as an exciton from HOMO to LUMO derived states. Both satellite features are still visible for 1.3 ML C 60 but they are not present in the 0.9 ML film, which is consistent with the fact that chemisorption of the C 60 molecules in the first layer involves mixing of the molecular and substrate levels in the initial and final states [27]. For 0.9 ML C 60 , the C 1s peak displays an asymmetric line shape.…”

Section: Resultssupporting

confidence: 67%

Charge-transfer dynamics in one-dimensional C60 chains

Pérez-Dieste¹,

Tamai²,

Greber³

et al. 2008

Surface Science

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Charge transfer in highly-ordered C60 chains grown on a Cu(5 5 3) vicinal surface is studied by means of resonant photoemission. Tuning the light polarization, autoionization of the highest occupied molecular orbital (HOMO) was expected to detect anisotropy in this one-dimensional system. For one monolayer C60 we found no signature of autoionization. This indicates that for an electron which is excited from the C 1s level of C60 to the lowest unoccupied molecular orbital (LUMO), hybridization leads to delocalization on the femtosecond time-scale and no influence of the light polarization is observed. Charge-transfer Dynamics in AbstractCharge transfer in highly-ordered C 60 chains grown on a Cu(553) vicinal surface is studied by means of resonant photoemission. Tuning the light polarization, autoionization of the highest occupied molecular orbital (HOMO) was expected to detect anisotropy in this one-dimensional system. For one monolayer C 60 we found no signature of autoionization. This indicates that for an electron which is excited from the C 1s level of C 60 to the lowest unoccupied molecular orbital (LUMO), hybridization leads to delocalization on the femtosecond time-scale and no influence of the light polarization is observed.

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Section: Resultssupporting

confidence: 67%

Charge-transfer dynamics in one-dimensional C60 chains

Pérez-Dieste¹,

Tamai²,

Greber³

et al. 2008

Surface Science

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“…The energy difference between E A and E I (the conductivity gap) is reduced by a factor of 2 when comparing the energy levels of an isolated molecule with those of a C 60 monolayer on Ag (111). Values taken from [13,21,[34][35][36][37][38][39] In the system depicted by Fig. 1c, the metal stabilizes the charged state of the C 60 -ion, since the metal effectively screens the ion.…”

Section: Introductionmentioning

confidence: 99%

On interface dipole layers between C 60 and Ag or Au

Veenstra

Heeres

Hadziioannou

et al. 2002

Applied Physics A: Materials Science & Processing

103

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C 60 layers on polycrystalline Ag and Au are studied by photoelectron spectroscopy. At these metal/C 60 interfaces an electron transfer occurs from the metal to the lowest unoccupied orbital of C 60 . We found in the case of the polycrystalline Ag/C 60 interface a dipolar layer with its associated electric field in the direction corresponding to the charge transfer, so pointing from the substrate to the adsorbent. Yet, at the Au/C 60 interface we observed an overall electric field pointing from C 60 towards the metal. We discuss our observations in terms of charge transfer, screening and hybridization effects and propose the occurrence of a hybridization mechanism similar to back-bonding at the Au/C 60 interface. We show that the alignment of energy levels at the metal/C 60 interface cannot simply be deduced using the metal workfunction and the frontier orbitals of C 60 , including screening effects, since hybridization effects may strongly alter the interfacial energy level structure. Our experimental findings on the polycrystalline metal/C 60 interfaces indicate an at-most weak dependence of the Fermi level of the C 60 overlayer on the workfunction of the polycrystalline metal substrate. These interfaces are found in donoracceptor-based organic photovoltaic devices and our results may help to understand the electrical characteristics of these devices.

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Section: Resultsmentioning

confidence: 99%

“…27,28 The XPS spectrum, therefore, is made up of an intense peak from the original ejected photoelectron, and a number of peaks on the high binding energy side of the main peak due to the energy loss for excitation of 32 all visible in the spectrum. (b) Molecular energy levels of C 60 (neglecting core hole ionization) (after Refs.…”

Section: Resultsmentioning

confidence: 99%

LiF Doping of C₆₀Studied with X-ray Photoemission Shake-Up Analysis

Turak

Zgierski

Dharma‐wardana

2017

ECS J. Solid State Sci. Technol.

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We report our investigation of the chemical doping mechanism induced by LiF interaction with fullerene thin films. High resolution Xray photoelectron spectroscopy of the C1s shake-up satellites and F1s main core level, supported by density functional calculations, suggest the formation of a charge transfer complex between covalent LiF monomers and dimers and C 60 . This interaction was observed in both LiF/C 60 and C 60 /LiF depositions, suggesting that some charge transfer complexation can occur in these systems even without dissociation. hydrogen storage materials, 5 and even antibacterial treatments. 6,7 Due to the rich electronic properties in the ground and excited states, C 60 is most widely used as an organic semiconductor. With the ability to act as both an electron acceptor and donor, it is a standard material in organic light emitting diodes, solar cells, transistors and Schottky diodes.The interface with the metal contacts play a crucial role in the effectiveness of organic semiconductors in device performance and stability.8 Introducing a thin buffer layer of LiF between an organic film and an Al cathode has been seen to dramatically enhance the energy-level alignment and stability of the interface.9-13 Additionally, alternating stacks of LiF and C 60 14 and LiF doped C 60 nanocomposite buffer layers 15,16 have been shown to have high conductivities and stability in OLEDs and OPVs. Several mechanisms have been proposed for these behaviors including chemical reactions, dipole alignment, tunneling, and LiF dissociation requiring the additional presence of Al. 17In this contribution, we present results showing that in the absence of Al, there is a charge transfer interaction between LiF and C 60 , leading to the formation of LiF••C 60 complexes without dissociation. Using the well-developed and described X-ray photoelectron shakeup structure of C 60 and the strong feature from F1s XPS core level, we see evidence of a direction independent interaction. The spectroscopic features can be described by the semi-covalent interaction of LiF monomers or dimers with C 60 using density functional theory. Coupled with XPS core level shift calculations, using approximate Madelung energy, the predicted Millikan charges and bond lengths give values that approximate the observed core level shifts. Additionally, the small transfer of charge to C 60 predicted by the modelling is consistent with the minimal impact on the shake-up satellites of the C1s of C 60 . ExperimentalThe samples were produced using a Kurt J. Lesker OLED cluster attached to an X-ray photoelectron spectroscopy tool. For deposition of C 60 , ∼5Å of LiF on 100 nm sputter deposited Au/Si was used z E-mail: turaka@mcmaster.ca as a substrate. For deposition of LiF, the substrate was 350Å of C 60 thermally deposited onto cleaned Si with native oxide. C 60 and LiF were thermally evaporated from home built crucible sources at an average rate of 1 Å/min and 2-3 Å/hr as measured by oscillating quartz crystal microbalance (Inficon XTM/2) respectively onto previ...

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C60bonding and energy-level alignment on metal and semiconductor surfaces

Cited by 324 publications

References 43 publications

Charge-transfer dynamics in one-dimensional C60 chains

Charge-transfer dynamics in one-dimensional C60 chains

On interface dipole layers between C 60 and Ag or Au

LiF Doping of C₆₀Studied with X-ray Photoemission Shake-Up Analysis

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C60bonding and energy-level alignment on metal and semiconductor surfaces

Cited by 324 publications

References 43 publications

Charge-transfer dynamics in one-dimensional C60 chains

Charge-transfer dynamics in one-dimensional C60 chains

On interface dipole layers between C 60 and Ag or Au

LiF Doping of C60Studied with X-ray Photoemission Shake-Up Analysis

Contact Info

Product

Resources

About

LiF Doping of C₆₀Studied with X-ray Photoemission Shake-Up Analysis