Electron transport properties of graphene with charged impurities and vacancy defects

Kudo, Yasuhiko; Takai, Kazuyuki; Enoki, Toshiaki

doi:10.1557/jmr.2013.62

Cited by 8 publications

(5 citation statements)

References 39 publications

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“…Contamination on the surface of 2D materials, such as boron nitride nanosheets (BNNS) and the graphene family of materials is detrimental to their intrinsic transport properties (e.g., thermal, electrical conduction) as they induce electron and phonon scattering, reducing electrical and thermal conduction. [1][2][3][4] Different approaches have been adopted to clean the surface of 2D materials from surface contaminants of the 2D material when freezing without adding any further water, as is normally required in the freeze drying process (method FD-(i)). Further details on each methodology are provided in the Experimental Section.…”

Section: Introductionmentioning

confidence: 99%

“…Contamination on the surface of 2D materials, such as boron nitride nanosheets (BNNS) and the graphene family of materials is detrimental to their intrinsic transport properties (e.g., thermal, electrical conduction) as they induce electron and phonon scattering, reducing electrical and thermal conduction. [ 1–4 ] Different approaches have been adopted to clean the surface of 2D materials from surface contaminants and impurities using methodologies such as electrical current annealing, [ 5 ] thermal annealing/desorption, [ 6–12 ] washing with water, acids, bases, ethanol, [ 12–14 ] plasma treatment, [ 13 ] and etching of metals. [ 15 ] Electrical annealing is effective at cleaning the surfaces of 2D materials; however, it is very limited in that it can only treat small sample areas (few micrometer square).…”

Section: Introductionmentioning

confidence: 99%

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Surface Cleaning of 2D Materials: Boron Nitride Nanosheets (BNNS) and Exfoliated Graphite Nanoplatelets (GNP)

Guerra

McNally

2020

Adv Materials Inter

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and impurities using methodologies such as electrical current annealing, [5] thermal annealing/desorption, [6-12] washing with water, acids, bases, ethanol, [12-14] plasma treatment, [13] and etching of metals. [15] Electrical annealing is effective at cleaning the surfaces of 2D materials; however, it is very limited in that it can only treat small sample areas (few micrometer square). [5] Thermal annealing proved to be the most effective at removing the impurities from the surface of 2D materials; however, there are serious concerns with regard degradation of the 2D material as a function of time. Washing with acids/bases are not always desirable as they can alter surface chemistry and their use may negatively impact the environment. [15] The etching of metals procedure is too laborious and not readily suitable for large-scale applications. Almost without exception the top-down production of 2D materials requires the use of surfactants or dispersants (e.g., water, ionic liquids) to assist the exfoliation of some bulk material. By way of example, the pretreatment of BNNS and exfoliated graphite nanoplatelets (GNP) studied here contain trace water and surfactant (sodium cholate, SC), [16,17] mainly introduced during the exfoliation of the corresponding bulk materials (i.e., boron nitride and graphite) in a high pressure homogenizer. [18] Specifically, three cleaning procedures were adopted in an attempt to remove impurities (i.e., water and SC) from the surfaces of BNNS and GNP, namely washing with ethanol, water assisted-freeze drying, and freeze drying without addition of water. Ethanol (EtOH) was utilized as it can wash water away from the surface of the BNNS and GNP and interact with the ionic surfactant SC thus being removed. The freeze drying process was selected as the sublimation of iced-water from the surface of BNNS and GNP would ideally remove water and exfoliate the 2D material further. [19-23] Indeed, when ice sublimates, the layers and flakes surrounded by ice are pulled apart. Two specific procedures for freeze drying were realized; FD-(i)-freezing of a dispersion of BNNS or GNP in water in liquid nitrogen followed by freeze drying and FD-(ii)-freezing in liquid nitrogen of the as received BNNS or GNP powder followed by freeze drying. The latter was performed on the basis that the water present as impurity in the BNNS and GNP samples would be sufficient at creating an ice pattern cutting through the layered structure Surface impurities such as water and surfactants can significantly affect the properties of 2D materials. They disrupt the 2D material lattice structure and surface chemistry and also promote electron and phonon scattering. Strategies to clean the surfaces of 2D materials are therefore critical to achieving optimal properties. Boron nitride nanosheets (BNNS) and exfoliated graphite nanoplatelets (GNP) are treated using three procedures: washing with ethanol, water-assisted freeze-drying, and freeze-drying without addition of water in an attempt to remove two impurities-water and an ion...

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Section: Introductionmentioning

confidence: 99%

“…Contamination on the surface of 2D materials, such as boron nitride nanosheets (BNNS) and the graphene family of materials is detrimental to their intrinsic transport properties (e.g., thermal, electrical conduction) as they induce electron and phonon scattering, reducing electrical and thermal conduction. [ 1–4 ] Different approaches have been adopted to clean the surface of 2D materials from surface contaminants and impurities using methodologies such as electrical current annealing, [ 5 ] thermal annealing/desorption, [ 6–12 ] washing with water, acids, bases, ethanol, [ 12–14 ] plasma treatment, [ 13 ] and etching of metals. [ 15 ] Electrical annealing is effective at cleaning the surfaces of 2D materials; however, it is very limited in that it can only treat small sample areas (few micrometer square).…”

Section: Introductionmentioning

confidence: 99%

Surface Cleaning of 2D Materials: Boron Nitride Nanosheets (BNNS) and Exfoliated Graphite Nanoplatelets (GNP)

Guerra

McNally

2020

Adv Materials Inter

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“…As the properties of 2D materials have been shown to be sensitive to the substrate, surface defects, and impurities, graphene, TMD, and h‐BN surface cleaning and preparation procedures are critically needed . However, relatively few investigations of h‐BN surface cleaning have been reported, and most of these have focused on pure thermal annealing/desorption procedures .…”

Section: Introductionmentioning

confidence: 99%

Cleaning of pyrolytic hexagonal boron nitride surfaces

King

Nemanich

Davis

2015

Surface & Interface Analysis

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Hexagonal boron nitride (h-BN) has recently garnered significant interest as a substrate and dielectric for two-dimensional materials and devices based on graphene or transition metal dichalcogenides such as molybdenum disulfide (MoS 2 ). As substrate surface impurities and defects can negatively impact the structure and properties of two-dimensional materials, h-BN surface preparation and cleaning are a critical consideration. In this regard, we have utilized X-ray photoelectron spectroscopy to investigate the influence of several ex situ wet chemical and in situ thermal desorption cleaning procedures on pyrolytic h-BN surfaces. Of the various wet chemistries investigated, a 10 : 1 buffered HF solution was found to produce surfaces with the lowest amount of oxygen and carbon contamination. Ultraviolet/ozone oxidation was found to be the most effective ex situ treatment for reducing carbon contamination. Annealing at 1050°C in vacuum or 10 À5 Torr NH 3 was found to further reduce oxygen and carbon contamination to the XPS detection limits.

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“…1 Recently, the oxidation of graphene has been of particular interest because the band gap is opened by oxidation, which makes it possible to utilize graphene for high-performance transistor devices, 2,3 and because graphene oxidation is a promising technique to prepare various types of graphene, including nano-hole and anti-dot graphene. [4][5][6][7][8] Oxidation and subsequent reduction are prevalent techniques for fabricating graphene of a large size. 4 In practical applications of graphene and graphite, such as batteries, catalysis, and gas absorbers, 5 graphene is handled in the ambient atmosphere, so that the edges of graphene are seriously oxidized with the majority of the edge carbon atoms bonded to oxygencontaining functional groups.…”

Section: Introductionmentioning

confidence: 99%

Preferential oxidation-induced etching of zigzag edges in nanographene

Takashiro

Kudo

Hao

et al. 2014

Phys. Chem. Chem. Phys.

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We investigated the thermal oxidation process of nanographene using activated carbon fibers (ACFs) by thermogravimetry (TG), X-ray photoemission spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS), and electrical conductance measurements. The oxidation process started from the edge of nanographene with the formation of phenol (-OH) or ether (C-O-C) groups attached to edge carbon atoms, as verified by the XPS and NEXAFS results. While the TG results indicated a decrease in the size of the nanographene sheet during the oxidation process, the intensity of the edge-state peak, i.e., the signature of the zigzag edge, decreased in the C K-edge NEXAFS spectra. This suggests that the zigzag edge preferentially reacted with oxygen and that the nanographene terminated with the thermodynamically unstable zigzag edges converted to one terminated with stable armchair edges. As the oxidation temperature increased, the activation energy for the electron hopping transport governed by the Coulomb gap variable range hopping between the nanographene sheets increased, and the tunneling barrier decreased. This change can be understood on the basis of the decrease in the size of the nanographene sheets together with the preferential etching of nanographene edges and the decrease in the inter-nanographene-sheet distance.

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Electron transport properties of graphene with charged impurities and vacancy defects

Abstract: Abstract

Cited by 8 publications

References 39 publications

Surface Cleaning of 2D Materials: Boron Nitride Nanosheets (BNNS) and Exfoliated Graphite Nanoplatelets (GNP)

Surface Cleaning of 2D Materials: Boron Nitride Nanosheets (BNNS) and Exfoliated Graphite Nanoplatelets (GNP)

Cleaning of pyrolytic hexagonal boron nitride surfaces

Preferential oxidation-induced etching of zigzag edges in nanographene

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