Re-evaluating how charge transfer modifies the conformation of adsorbed molecules

Blowey, Phil J.; Velari, Simone; Rochford, Luke A.; Duncan, David A.; Warr, Daniel; Lee, TL; Vita, Alessandro De; Costantini, Giovanni; Woodruff, D.P.

doi:10.1039/c8nr02237b

Cited by 38 publications

(87 citation statements)

References 56 publications

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“…The NIXSW technique, with the X-ray absorption monitored by the resulting core level photoemission signal, provides a method of determining the height above a surface of the atoms within an element-specific and chemical-state-specific fashion [8]. A detailed structural analysis of the LDC phase, based on a combination of NIXSW data and the results of DFT calculations has already been published [9]. A similar DFT simulation of the HDI phase is not possible because these calculations rely on having a commensurate molecular superstructure.…”

Section: Nixsw Resultsmentioning

confidence: 99%

“…However, NIXSW can be applied to such a system and a their fits, are shown in Fig. S2 in the supplemental material [22], also compared with the experimental data for the LDC phase and their fits [9]. All parameter values are very similar for the two different structural phases.…”

Section: Nixsw Resultsmentioning

confidence: 99%

“…As indicated in the introduction, a full structure determination of the LDC phase has already been published [9]. The only previously reported observations of the HDI phase appear to be in the paper of Wäckerlin et al [17], who presented an STM image that shows a similar ordering of molecular features, and in a later PhD thesis [18].…”

Section: Surface Characterisationmentioning

confidence: 99%

“…intensity. An alternative possibility is some modification in the underlying Ag(111) surface geometry, by the addition or removal of Ag adatoms (identified as an ingredient of the LDC structure [9] and previously speculated to occur in the HDI phase [17]) or by a change in the surface corrugation. In view of the much higher atomic number of the Ag atoms, and of the consequential larger scattering cross-section, rearrangement of these atoms may be a more likely cause of the change in the LEEM intensity (and in the entire LEEM-I-V curve).…”

Section: Leem Study Of the Tcnq Adsorption Phasesmentioning

confidence: 99%

“…Evidence from experimental studies, particularly using X-ray photoelectron spectroscopy (XPS), has indicated that this electron transfer occurs on a number of coinage metal surfaces, and density functional theory (DFT) calculations have predicted that the resulting flexible molecule bends into an inverted bowl configuration with the N atoms as much as 1.4 Å below the central quinoid ring [1,2,3,4,5,6,7]. phase of TCNQ adsorbed on Ag(111) using normal incidence X-ray standing waves (NIXSW) [8] and showed that the molecule does not adopt this bent configuration in this phase [9]. Through comparison of the NIXSW data with dispersion-corrected DFT calculations we concluded that instead the adsorbed molecule twists such that some C-N are tilted out of the surface to bond to Ag adatoms, while other C-N bonds tilt down to bond to the Ag atoms in the underlying surface.…”

Section: Introductionmentioning

confidence: 99%

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Characterization of growth and structure of TCNQ phases on Ag(111)

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Section: Nixsw Resultsmentioning

confidence: 99%

Section: Nixsw Resultsmentioning

confidence: 99%

Section: Surface Characterisationmentioning

confidence: 99%

Section: Leem Study Of the Tcnq Adsorption Phasesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Characterization of growth and structure of TCNQ phases on Ag(111)

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Haags

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et al. 2019

Phys. Rev. Materials

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Engineering of Printable and Air‐Stable Silver Electrodes with High Work Function using Contact Primer Layer: From Organometallic Interphases to Sharp Interfaces

Widdascheck

Bischof

Witte

2021

Adv Funct Materials

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Contact engineering is an important issue for organic electronics as it allows to reduce charge carrier injection barriers. While the use of molecular contact primer layers to control the energy level alignment is demonstrated in many concept studies, mainly using (single crystalline) model substrates, the processability of electrodes and their robustness must also be considered in real devices. Although silver electrodes can be printed using silver ink, their low work function and sensitivity to oxidation severely limits their use for printable organic electronics. The present study demonstrates that mono layers of F 4 TCNQ and F 6 TCNNQ provide a reliable approach to engineer high work function silver electrodes, which is examined for Ag(111) as well as polycrystalline and silver ink substrates. Notably, upon multilayer growth, a pronounced intercalation of silver into the molecular adlayer occurs, yielding thermally stabilized organometallic interphases extending over the entire adlayer. It is shown that heating allows their controlled desorption leaving behind a well-defined monolayer that is further stabilized by additional charge transfer. Especially F 6 TCNNQ contact primer layers can also be prepared on oxidized silver electrodes yielding work functions of 5.5-5.6 eV, which can even withstand air exposure. Such contact primers show no interdiffusion into subsequently deposited layers of the prototypical p-type organic semiconductor pentacene, hence validating their use for organic electronic devices.

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Electrostatically Designing Materials and Interfaces

Zojer

2024

Advanced Materials

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Collective electrostatic effects arise from the superposition of electrostatic potentials of periodically arranged (di)polar entities and are known to crucially impact the electronic structures of hybrid interfaces. Here, it is discussed, how they can be used outside the beaten paths of materials design for realizing systems with advanced and sometimes unprecedented properties. The versatility of the approach is demonstrated by applying electrostatic design not only to metal‐organic interfaces and adsorbed (complex) monolayers, but also to inter‐layer interfaces in van der Waals heterostructures, to polar metal‐organic frameworks (MOFs), and to the cylindrical pores of covalent organic frameworks (COFs). The presented design ideas are straightforward to simulate and especially for metal‐organic interfaces also their experimental implementation has been amply demonstrated. For van der Waals heterostructures, the needed building blocks are available, while the required assembly approaches are just being developed. Conversely, for MOFs the necessary growth techniques exist, but more work on advanced linker molecules is required. Finally, COF structures exist that contain pores decorated with polar groups, but the electrostatic impact of these groups has been largely ignored so far. All this suggest that the dawn of the age of electrostatic design is currently experienced with potential breakthroughs lying ahead.

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Re-evaluating how charge transfer modifies the conformation of adsorbed molecules

Abstract: A combined quantitative experimental and theoretical structure determination shows TCNQ is not bent on Ag(111) as expected from conventional wisdom.

Cited by 38 publications

References 56 publications

Characterization of growth and structure of TCNQ phases on Ag(111)

Characterization of growth and structure of TCNQ phases on Ag(111)

Engineering of Printable and Air‐Stable Silver Electrodes with High Work Function using Contact Primer Layer: From Organometallic Interphases to Sharp Interfaces

Electrostatically Designing Materials and Interfaces

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