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

Abstract

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.

Ultraclean and Facile Patterning of CVD Graphene by a UV-Light-Assisted Dry Transfer Method

“…The I D /I G peak ratio (Figure 3a) of ∼0.04 indicates that the three transfer methods do not cause large defects in the graphene. 32 Furthermore, the correlation between the Raman frequencies of the G (ω G ) and 2D (ω 2D ) modes of various samples was employed to characterize the strain and doping effect on the transferred graphene (Figure 3b). 33 Figure 3b shows that the dry transfer methods (TRT and UV-RT) involve an R2R pressing process, which exerts a tensile strain on the graphene film.…”

“…To discuss the degree of defects and residues on graphene after the transfer process, Raman spectroscopy was used to analyze the above three kinds of samples. The I D / I G peak ratio (Figure a) of ∼0.04 indicates that the three transfer methods do not cause large defects in the graphene . Furthermore, the correlation between the Raman frequencies of the G (ω G ) and 2D (ω 2D ) modes of various samples was employed to characterize the strain and doping effect on the transferred graphene (Figure b) …”

Precise synthesis of graphene by chemical vapor deposition

“…In 2022, He et al adopted a fluorinated-self-assembled-monolayer (FSAM)-modified SiO 2 /Si substrate by a dry-transfer process to achieve wrinkle-free graphene. 81 The lower surface energy of the FSAM allowed the wrinkled graphene to spread out under heat between graphene and the substrate, and thus wrinkle-free graphene was achieved (Fig. 22c).…”

A flexible transparent graphene/metal–organic framework complex hybrid chemical sensor for highly sensitive ethanol detection

“…14,15 Therefore, graphene is a suitable material for high-speed, flexible, and transparent future electronic devices. Based on the excellent electrical properties of graphene, many studies on the application of electronic devices including field-effect transistors (FETs), [16][17][18] capacitors, 19,20 photovoltaic cells, 21,22 light-emitting diodes, 23,24 and sensors [25][26][27][28][29][30][31] have been conducted. Among these, chemical sensors that detect volatile organic compounds have been used as important and practical tools including personal healthcare monitoring tools as well as environmental monitoring tools in industrial applications.…”