Impact of Graphene Work Function on the Electronic Structures at the Interface between Graphene and Organic Molecules

Wang, Haitao; Yang, Xinling; Dou, Weidong; Wang, Peng; Ye, Quan‐Lin; Yang, Xiaoqing; Li, Baoxing; Mao, Hongying

doi:10.3390/nano9081136

Cited by 8 publications

(5 citation statements)

References 49 publications

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“…In this regard, to further investigate the impact of molecular orientation on energylevel alignment in organic electronic devices, we conducted a study in which we controlled the thickness of a HAT-CN layer (5 nm and 100 nm) and examined its effect on the molecular orientation of a layer of zinc phthalocyanine (ZnPc), a representative p-type organic semiconductor [30]. ZnPc is widely used in optoelectronic devices, including field-effect transistors and solar cells [31][32][33][34][35][36].…”

Section: Introductionmentioning

confidence: 99%

Effects of HAT-CN Layer Thickness on Molecular Orientation and Energy-Level Alignment with ZnPc

Joo

Hur

et al. 2023

Molecules

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Efficient energy-level alignment is crucial for achieving high performance in organic electronic devices. Because the electronic structure of an organic semiconductor is significantly influenced by its molecular orientation, comprehensively understanding the molecular orientation and electronic structure of the organic layer is essential. In this study, we investigated the interface between a 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HAT-CN) hole injection layer and a zinc-phthalocyanine (ZnPc) p-type organic semiconductor. To determine the energy-level alignment and molecular orientation, we conducted in situ ultraviolet and X-ray photoelectron spectroscopies, as well as angle-resolved X-ray absorption spectroscopy. We found that the HAT-CN molecules were oriented relatively face-on (40°) in the thin (5 nm) layer, whereas they were oriented relatively edge-on (62°) in the thick (100 nm) layer. By contrast, ZnPc orientation was not significantly altered by the underlying HAT-CN orientation. The highest occupied molecular orbital (HOMO) level of ZnPc was closer to the Fermi level on the 100 nm thick HAT-CN layer than on the 5 nm thick HAT-CN layer because of the higher work function. Consequently, a considerably low energy gap between the lowest unoccupied molecular orbital level of HAT-CN and the HOMO level of ZnPc was formed in the 100 nm thick HAT-CN case. This may improve the hole injection ability of the anode system, which can be utilized in various electronic devices.

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Section: Introductionmentioning

confidence: 99%

Effects of HAT-CN Layer Thickness on Molecular Orientation and Energy-Level Alignment with ZnPc

Joo

Hur

et al. 2023

Molecules

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“…The aforementioned issues hinder their practical applications on the following device integration. Compared to the surface-limited hBN substrate, the self-assembled monolayer (SAM) has been widely used for tailoring the electrical properties of 2 DMs with a simple and scalable preparation and area-selectable modification on the substrate for lowering charge inhomogeneity and contaminant absorption. − In this regard, the different functional groups, such as −CH 3 , ,,− −NH 2 , ,,,,,− and −CF 3 ,,,− at the end of the silane molecular chain, have been reported to prepare the SAM-modified substrates, which can present improved electrical characteristics for the graphene. For example, n-type and p-type tailoring of graphene was observed when it was placed on the NH 2 -SAM- and the CF 3 -SAM-modified substrate accordingly due to the diverse charge transfers ( i.e.…”

Section: Introductionmentioning

confidence: 99%

“…Even though the mechanism of charge transfer at the interface of graphene/SAM has been well-known, the correlation between the electrical properties and their surface morphology, especially based on the dry transfer process, has still not yet been explored and fully investigated. Furthermore, the aforementioned SAM layer structures are usually prepared by heating the solid- or liquid-phase precursors and then evaporating onto target substrates in a sealed container ,,, or immersing the substrate in the solution for several hours to obtain high-quality SAM layers. , These methods are limited by their large-area nonuniformity and lower throughput, making it difficult to integrate them into the current integrated circuit (IC) fabrication procedure. Herein, we present new findings for achieving wrinkle-free graphene when transferring it onto the designed FSAM-modified substrate with a dry transfer method, where the FSAM is formed by immersing the target substrate in the trichloro(1 H ,1 H ,2 H ,2 H -perfluorooctyl)silane (FDTS) solution with our optimized conditions (dipping time and concentration).…”

Section: Introductionmentioning

confidence: 99%

“…29 Even though the mechanism of charge transfer at the interface of graphene/ SAM has been well-known, the correlation between the electrical properties and their surface morphology, especially based on the dry transfer process, has still not yet been explored and fully investigated. Furthermore, the aforementioned SAM layer structures are usually prepared by heating the solid-or liquid-phase precursors and then evaporating onto target substrates in a sealed container 7,17,23,29 or immersing the substrate in the solution for several hours to obtain highquality SAM layers. 11,20 These methods are limited by their large-area nonuniformity and lower throughput, making it difficult to integrate them into the current integrated circuit (IC) fabrication procedure.…”

Section: Introductionmentioning

confidence: 99%

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Wrinkle-Free Graphene Films on Fluorinated Self-Assembled Monolayer-Modified Substrates for Enhancing the Electrical Performance of Transistors

Lin

Shen

et al. 2022

ACS Appl. Nano Mater.

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Self-assembled monolayer (SAM)-functionalized substrates are widely used for tailoring the electronic properties (i.e., p- and n-type doping) of two-dimensional materials, which might suppress the charge scattering, impurities, and wrinkles that can severely decline electrical properties. The fluorinated self-assembled monolayer (FSAM) is also used for promoting electrical properties by eliminating the small number of water molecules/residues between the substrate and graphene during the typical wet transfer process. However, taking graphene as an example, most of the graphene/SAM or graphene/FSAM studies are focused on the enhancement of their electrical properties and lack investigation on their surface morphology after transfer and the correlation between them. Herein, a strategy is discovered in which FSAM-modified substrates help construct a wrinkle-free graphene film with the dry transfer process due to the low surface energy between the graphene and FSAM. Trichloro(1H,1H,2H,2H-perfluorooctyl)silane (FDTS) was selected as a precursor toward the formation of the monolayer and highly uniform FSAM using a facile dip-coating route, which is feasible on versatile substrates such as Si, SiO2/Si, and poly(ethylene terephthalate) (PET). The surface roughness of the FSAM-modified SiO2 substrate reduces from 2.98 to 0.13 nm. Therefore, the lower surface energy (from 60.80 to 8.12 mN/m) was found to enhance the carrier mobility of the transferred graphene by about 1.77 times, increasing from 894.6 to 1588 cm2/(V·s). Furthermore, a top-gated field-effect transistor based on graphene/FSAM was fabricated and characterized in which the FSAM decouples from the strong substrate interference and significantly improved the field-effect mobility by up to 17 times compared to that of graphene without substrate modification. Thus, this work provides a facile strategy to avoid wrinkle defects and suppress charge scattering through the decoupling from the substrate, which could be applied to other two-dimensional (2D) materials for improving their electrical performance on transistors and flexible electronics.

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“…Self-assembled monolayers (SAMs) have been the subject of intense studies due to their promising applications in microelectromechanicalsystems (MEMS), molecular electronics, wetting, lubrication, and corrosion inhibition [1][2][3][4][5]. The formation of SAMs on various kinds of substrates has been investigated intensively [6,7].…”

Section: Introductionmentioning

confidence: 99%

Thermal Stability of Octadecyltrichlorosilane and Perfluorooctyltriethoxysilane Monolayers on SiO2

Yang

Wang

et al. 2020

Nanomaterials

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Using in situ ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS) measurements, the thermal behavior of octadecyltrichlorosilane (OTS) and 1H, 1H, 2H, and 2H-perfluorooctyltriethoxysilane (PTES) monolayers on SiO2 substrates has been investigated. OTS is thermally stable up to 573 K with vacuum annealing, whereas PTES starts decomposing at a moderate temperature between 373 K and 423 K. Vacuum annealing results in the decomposition of CF3 and CF2 species rather than desorption of the entire PTES molecule. In addition, our UPS results reveal that the work function (WF)of OTS remains the same after annealing; however WF of PTES decreases from ~5.62 eV to ~5.16 eV after annealing at 573 K.

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Impact of Graphene Work Function on the Electronic Structures at the Interface between Graphene and Organic Molecules

Cited by 8 publications

References 49 publications

Effects of HAT-CN Layer Thickness on Molecular Orientation and Energy-Level Alignment with ZnPc

Effects of HAT-CN Layer Thickness on Molecular Orientation and Energy-Level Alignment with ZnPc

Wrinkle-Free Graphene Films on Fluorinated Self-Assembled Monolayer-Modified Substrates for Enhancing the Electrical Performance of Transistors

Thermal Stability of Octadecyltrichlorosilane and Perfluorooctyltriethoxysilane Monolayers on SiO2

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