Abstract:With its exceptional charge mobility, graphene holds great promise for applications in next-generation electronics. In an effort to tailor its properties and interfacial characteristics, the chemical functionalization of graphene is being actively pursued. The oxidation of graphene via the Hummers method is most widely used in current studies, although the chemical inhomogeneity and irreversibility of the resulting graphene oxide compromises its use in high-performance devices. Here, we present an alternative … Show more
“…One approach is the nano-engineering of graphene to form nano-ribbons so that charge carriers are confined to a quantum wire 2,3 . A more scalable approach is the formation of chemical derivatives such as graphene oxide (GO) 4,5 , hydrogenated graphane (CH) 6 or fluorinated graphene (C x F, xr4) [7][8][9] . GO consists of graphene sheets decorated with epoxy, hydroxyl and carboxyl groups 4 , whereas graphane is hydrogenated graphene 6 .…”
One of the most desirable goals of graphene research is to produce ordered two-dimensional (2D) chemical derivatives of suitable quality for monolayer device fabrication. Here we reveal, by focal series exit wave reconstruction (EWR), that C 2 F chair is a stable graphene derivative and demonstrates pristine long-range order limited only by the size of a functionalized domain. Focal series of images of graphene and C 2 F chair formed by reaction with XeF 2 were obtained at 80 kV in an aberration-corrected transmission electron microscope. EWR images reveal that single carbon atoms and carbon-fluorine pairs in C 2 F chair alternate strictly over domain sizes of at least 150 nm 2 with electron diffraction indicating ordered domains Z0.16 mm 2 . Our results also indicate that, within an ordered domain, functionalization occurs on one side only as theory predicts. In addition, we show that electron diffraction provides a quick and easy method for distinguishing between graphene, C 2 F chair and fully fluorinated stoichiometric CF 2D phases.
“…One approach is the nano-engineering of graphene to form nano-ribbons so that charge carriers are confined to a quantum wire 2,3 . A more scalable approach is the formation of chemical derivatives such as graphene oxide (GO) 4,5 , hydrogenated graphane (CH) 6 or fluorinated graphene (C x F, xr4) [7][8][9] . GO consists of graphene sheets decorated with epoxy, hydroxyl and carboxyl groups 4 , whereas graphane is hydrogenated graphene 6 .…”
One of the most desirable goals of graphene research is to produce ordered two-dimensional (2D) chemical derivatives of suitable quality for monolayer device fabrication. Here we reveal, by focal series exit wave reconstruction (EWR), that C 2 F chair is a stable graphene derivative and demonstrates pristine long-range order limited only by the size of a functionalized domain. Focal series of images of graphene and C 2 F chair formed by reaction with XeF 2 were obtained at 80 kV in an aberration-corrected transmission electron microscope. EWR images reveal that single carbon atoms and carbon-fluorine pairs in C 2 F chair alternate strictly over domain sizes of at least 150 nm 2 with electron diffraction indicating ordered domains Z0.16 mm 2 . Our results also indicate that, within an ordered domain, functionalization occurs on one side only as theory predicts. In addition, we show that electron diffraction provides a quick and easy method for distinguishing between graphene, C 2 F chair and fully fluorinated stoichiometric CF 2D phases.
“…oxygen and hydroxyl and carboxyl) to the graphene surface. Due to the chemical inhomogeneity and irreversibility of the resulting GO, an alternative approach using atomic oxygen in ultrahigh vacuum is presented for reversible and uniform oxidation of epitaxial graphene on SiC(0001) [345]. Specifically, the oxidation degree of epitaxial graphene or the density of chemisorbed oxygen (see Figure 19(a)) can be readily tuned by controlling the duration of atomic oxygen exposure.…”
Section: Modulation Of Structural Defects In Graphenementioning
confidence: 99%
“…In addition, the chemisorbed oxygen on epitaxial graphene can be reversibly removed by annealing the oxidized surface at 260 °C as well as by energetic electrons from the STM tips, as shown in the STM images in Figure 19(b,c). 10.1080/14686996.2018.1494493-F0019Figure 19.(a) Configuration of chemisorbed oxygen on graphene sheet, which corresponds to bright protrusions in bottom Auger electron spectroscopy (AES) image [345]. STM images of UHV oxidized epitaxial graphene after (b) annealing at 260 °C and (c) reversibly desorbed by injecting electrons from the STM tip at a sample bias of + 4V and tunneling current of 1 nA [345].…”
Section: Modulation Of Structural Defects In Graphenementioning
confidence: 99%
“…(a) Configuration of chemisorbed oxygen on graphene sheet, which corresponds to bright protrusions in bottom Auger electron spectroscopy (AES) image [345]. STM images of UHV oxidized epitaxial graphene after (b) annealing at 260 °C and (c) reversibly desorbed by injecting electrons from the STM tip at a sample bias of + 4V and tunneling current of 1 nA [345].…”
Section: Modulation Of Structural Defects In Graphenementioning
confidence: 99%
“…STM images of UHV oxidized epitaxial graphene after (b) annealing at 260 °C and (c) reversibly desorbed by injecting electrons from the STM tip at a sample bias of + 4V and tunneling current of 1 nA [345]. (d) Schematic of postulated nitrogenation on graphene [346].…”
Section: Modulation Of Structural Defects In Graphenementioning
Monolayer graphene exhibits extraordinary properties owing to the unique, regular arrangement of atoms in it. However, graphene is usually modified for specific applications, which introduces disorder. This article presents details of graphene structure, including sp2 hybridization, critical parameters of the unit cell, formation of σ and π bonds, electronic band structure, edge orientations, and the number and stacking order of graphene layers. We also discuss topics related to the creation and configuration of disorders in graphene, such as corrugations, topological defects, vacancies, adatoms and sp3-defects. The effects of these disorders on the electrical, thermal, chemical and mechanical properties of graphene are analyzed subsequently. Finally, we review previous work on the modulation of structural defects in graphene for specific applications.
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