Efros-Shklovskii variable-range hopping in reduced graphene oxide sheets of varying carbon<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>s</mml:mi><mml:msup><mml:mi>p</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:mrow></mml:math>fraction

Joung, Daeha; Khondaker, Saiful I.

doi:10.1103/physrevb.86.235423

Cited by 196 publications

(148 citation statements)

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“…Also, our transmission electron microscopic images 22 suggest that the ribbons have a nonuniform structure. The VRH-type electron transport mechanism has also been reported in several other graphene-derived materials such as reduced graphene oxide 23 and patterned GNR. From the slope of the VRH-fitting, the characteristic temperature (T o ) is estimated at ∼784 K. Previous studies 23 have reported the characteristic temperature as high as 1800 K in highly reduced graphene oxide materials.…”

Section: Resultsmentioning

confidence: 93%

“…The VRH-type electron transport mechanism has also been reported in several other graphene-derived materials such as reduced graphene oxide 23 and patterned GNR. From the slope of the VRH-fitting, the characteristic temperature (T o ) is estimated at ∼784 K. Previous studies 23 have reported the characteristic temperature as high as 1800 K in highly reduced graphene oxide materials. From T o , the localization length ξ , an indication of edge disorder, is estimated by,…”

Section: Resultsmentioning

confidence: 93%

“…The localization length derived here is in good agreement with those of literature values ranging from 7 nm to 7 μm. 23,25 The ξ values obtained in VRH allowed us to estimate the bandgap (Eg) by…”

Section: Resultsmentioning

confidence: 99%

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Magnetic defects in chemically converted graphene nanoribbons: electron spin resonance investigation

et al. 2014

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Electronic spin transport properties of graphene nanoribbons (GNRs) are influenced by the presence of adatoms, adsorbates and edge functionalization. To improve the understanding of the factors that influence the spin properties of GNRs, local (element) spin-sensitive techniques such as electron spin resonance (ESR) spectroscopy are important for spintronics applications. Here, we present results of multi-frequency continuous wave (CW), pulse and hyperfine sublevel correlation (HYSCORE) ESR spectroscopy measurements performed on oxidatively unzipped graphene nanoribbons (GNRs), which were subsequently chemically converted (CCGNRs) with hydrazine. ESR spectra at 336 GHz reveal an isotropic ESR signal from the CCGNRs, of which the temperature dependence of its line width indicates the presence of localized unpaired electronic states. Upon functionalization of CCGNRs with 4-nitrobenzene diazonium tetrafluoroborate, the ESR signal is found to be 2 times narrower than that of pristine ribbons. NH3 adsorption/desorption on CCGNRs is shown to narrow the signal, while retaining the signal intensity and g value. The electron spin-spin relaxation process at 10 K is found to be characterized by slow (163 ns) and fast (39 ns) components. HYSCORE ESR data demonstrate the explicit presence of protons and 13C atoms. With the provided identification of intrinsic point magnetic defects such as proton and 13C has been reported, which are roadblocks to spin travel in graphene-based materials, this work could help in advancing the present fundamental understanding on the edge-spin (or magnetic)-based transport properties of CCGNRs.

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Section: Resultsmentioning

confidence: 93%

Section: Resultsmentioning

confidence: 93%

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Magnetic defects in chemically converted graphene nanoribbons: electron spin resonance investigation

et al. 2014

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“…Such sp 2 fraction tuning can also lead to a variation of work function and bandgap of RGO. [18][19][20][21][22][23][24] However, how the variation of carbon sp 2 fraction of RGO will affect the performance of RGO-contacted OFETs remains unexplored.…”

mentioning

confidence: 99%

“…21 The carbon sp 2 fraction was calculated as 61%, 66%, and 80% for 10, 30, and 60 min of reduction time of RGO sheets, respectively. The carbon sp 2 fraction was obtained by taking the ratio of the integrated peak areas corresponding to the C-C peak, to the total area under the C 1s spectrum from the X-ray photoelectron spectroscopy (XPS) ( Figure S1 in the supplementary material).…”

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The impact of carbon sp2 fraction of reduced graphene oxide on the performance of reduced graphene oxide contacted organic transistors

Kang

Khondaker

2014

Applied Physics Letters

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One of the major bottlenecks in fabricating high performance organic field effect transistors (OFETs) is a large interfacial contact barrier between metal electrodes and organic semiconductors (OSCs) which makes the charge injection inefficient. Recently, reduced graphene oxide (RGO) has been suggested as an alternative electrode material for OFETs. RGO has tunable electronic properties and its conductivity can be varied by several orders of magnitude by varying the carbon sp2 fraction. However, whether the sp2 fraction of RGO in the electrode affects the performance of the fabricated OFETs is yet to be investigated. In this study, we demonstrate that the performance of OFETs with pentacene as OSC and RGO as electrode can be continuously improved by increasing the carbon sp2 fraction of RGO. When compared to control palladium electrodes, the mobility of the OFETs shows an improvement of ∼200% for 61% sp2 fraction RGO, which further improves to ∼500% for 80% RGO electrode. Similar improvements were also observed in current on-off ratio, on-current, and transconductance. Our study suggests that, in addition to π-π interaction at RGO/pentacene interface, the tunable electronic properties of RGO electrode have a significant role in OFETs performance.

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Conductive Graphitic Channel in Graphene Oxide‐Based Memristive Devices

Kim

Jang

et al. 2016

Adv Funct Materials

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wileyonlinelibrary.comdichalcogenides (TMDs), [11][12][13] and black phosphorous, [ 14 ] have been highlighted as promising candidates. Among these materials, graphene oxide (GO) has been extensively studied to develop electronic devices based on atomically thin fi lms. The high-quality thin fi lms via a simple and cost-effective solution process are easily fabricated onto transparent and fl exible substrates at the relatively low temperature. Furthermore, the electrical properties of fi lms can be controlled by the amount of oxygen-functional groups attached to the GO sheets. [15][16][17][18] Reduced graphene oxide (rGO) can be produced from electrically insulating GO by removing the oxygen groups via thermal and chemical reductions. Therefore, GO thin fi lms can be used as a promising active layer in resistive switching memories [ 10,[19][20][21] as well as fl exible electrodes with highly conductive rGO sheets. [ 9,10,22,23 ] Many research groups have reported on GObased resistive switching memories that show superior memory properties when sandwiched with different metal electrode materials. [19][20][21][24][25][26][27] Recently, GO hybrid composites mixed with other materials such as a polymer, [ 28,29 ] nanoparticles, [ 30,31 ] or other 2D materials [ 32 ] have been widely studied to improve the performance of GO-based memory.The microscopic origin of the resistive switching phenomenon in GO-based memories has been generally explained by oxygen ion migration and the formation of a metal fi lament within GO fi lms. Fundamental studies of this microscopic origin have been limited to electrical I -V measurements at various temperatures [ 10,18,21,23 ] or chemical analysis methods. [ 31,33,34 ] These methods differ from those used to directly demonstrate the switching mechanisms of conventional transition-metal-oxide-based memories, by applying highly resolved techniques such as local conductivity atomic force microscopy (LC-AFM), [ 35,36 ] scanning probe microscopy (SPM), [ 37 ] and transmission electron microscopy (TEM). [38][39][40] The measurement limitations in GO-based memories are due to practical challenges such as sample preparation of 2D stacked GO nanosheets for advanced characterization. Although we previously reported on the nanoscale Al metallic fi lament induced at the top amorphous interface layer in Al/GO/Al resistive memory devices using high-resolution TEM (HRTEM) techniques, [ 19,20 ] revealing the existence of conducting path in a GO active layer remains a diffi cult challenge. The ability to visualize the conductive fi lament induced in Electrically insulating graphene oxide with various oxygen-functional groups is a novel material as an active layer in resistive switching memories via reduction process. Although many research groups have reported on graphene oxide-based resistive switching memories, revealing the origin of conducting path in a graphene oxide active layer remains a critical challenge. Here nanoscale conductive graphitic channels within graphene oxide fi lms are reported us...

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Efros-Shklovskii variable-range hopping in reduced graphene oxide sheets of varying carbonsp2fraction

Cited by 196 publications

References 61 publications

Magnetic defects in chemically converted graphene nanoribbons: electron spin resonance investigation

Magnetic defects in chemically converted graphene nanoribbons: electron spin resonance investigation

The impact of carbon sp2 fraction of reduced graphene oxide on the performance of reduced graphene oxide contacted organic transistors

Conductive Graphitic Channel in Graphene Oxide‐Based Memristive Devices

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