Room‐Temperature Transport Properties of Graphene with Defects Derived from Oxo‐Graphene

Abstract

In recent years, graphene oxide has been considered as as oluble precursor of graphene for electronic applications. However,t he performance lags behind that of graphene due to lattice defects. Here, the relation between the density of defects in the range of 0.2 %a nd 1.5 %a nd the transport properties is quantitatively studied. Therefore, the related flakes of monolayers of graphene were prepared from oxo-functionalized graphene (oxo-G). The morphologic structure of oxo-G was imaged by atomicf orce microscopy (AFM) and scanning tunneling microscopy (STM). Field-effect mobility values were determined to range between 0.3 cm 2 V À1 s À1 and 33.2 cm 2 V À1 s À1 ,w hich were inverselyp roportionalt ot he density of defects. These resultsp rovide the first quantitative description of the density of defects and transport properties, which plays an important role for potentiala pplications.Chemically modified graphene, such as graphene oxide (GO) or oxo-functionalized graphene (oxo-G), has received considerable interests for electronic, [1] optoelectronic, [2] biological [3] and chemicals ensing [4] applications due to its physicochemical phenomena, including its tunable bandgap, [5] diverse luminescence behaviors, [6] biological compatibility [7] and the ability to modify the surfacec ovalently and non-covalently. [8] In contrast to pristine graphene with carbona toms arranged into at wodimensional hexagonal lattice, oxo-G consists of abundant sp 3hybridized carbon atoms, which are covalently bound to oxogroups,m ainly hydroxyl and epoxy groups. [9] The sp 3 -portioni s between 4% and6 0%,w ith variable functionality. [10] The oxoaddends are tentatively immobilizedo nto segregatedc arbon, which isolates intact nanometer-scale graphene domains into small islands. [11] The existence of surface oxo-groups has profound impacts on improving its hydrophilicity, [12] chemicalreactivity, [13] catalytic activity, [14] and optical properties, [2a] whereas the effect is detrimental for the electrical conductivity. [15] Therefore, to enhancet he electrical performance of GO or oxo-G, extensiver esearches were conducted on the deoxygenation of oxo-addends. [16] In this regard, thermal processing provides a simple and versatile method for carbonization, however,w ithout ac arbon source, more lattice defects, such as few-atoms vacancies and nanometer-scale holes, are introduced due to thermald isproportionation along with CO 2 formation. [17] Duringt he oxidative synthesis of GO and oxo-G, defects are introducedi nto the carbon framework. [10a] They cannot be healedo ut by simple chemical reduction although oxo-addendsa re reductively defunctionalized from the carbon lattice by ac hemical reductant. [18] The defect concentrationi nG Oo r oxo-G can be determined by Ramans pectroscopy after chemical reduction and typically varies from 0.001 %t o2%. [19] We demonstrated that the mobility of chargec arriers of reduced oxo-G with ad ensity of defects as low as 0.02 %i se xceeding 1000 cm 2 V À1 s À1 ,m easureda t1 .6 Ki na...

Interlayer electron modulation in van der Waals heterostructures assembled by stacking monolayer MoS2 onto monolayer graphene with different electron transfer ability

“…32 The intensity ratio I D /I G is approximately 3.5, which is used to determine the density of the defects (0.5%) in the r-oxo-G sample. 28 In Fig. 2B, two peaks, the in-plane E 1 2g (384.1 cm −1 ) and the out-of-plane A 1g (403.2 cm −1 ), appear in the Raman spectrum of the isolated 1L-MoS 2 layer.…”

“…25 It cannot be ignored that the decomposition and recombination of carbon atoms during the reduction process cause different in-plane defects including vacancies, holes, and non-six-membered carbon rings with sp 3 hybridization. 26,27 These defects, acting as structural motifs or active sites, can significantly change the electronic and surface properties of r-oxo-G. 28,29 In this work, we fabricated heterostructures of monolayer MoS 2 with three types of monolayer graphene: mechanically exfoliated graphene (1L-G), oxygen-functionalized graphene (1L-oxo-G), and chemically reduced oxo-G (1L-r-oxo-G). Raman and PL spectroscopy combined with Kelvin probe force microscopy (KPFM) measurements were carried out to study the optoelectronic properties and mechanism of interface interaction.…”

New Insight into the Characterization of Graphene Oxide and Reduced Graphene Oxide Monolayer Flakes on Si-Based Substrates by Optical Microscopy and Raman Spectroscopy

“…With the discovery and the development of graphene, graphene oxide (GO) and its reduced counterpart (reduced GORGO) has been regarded as the most promising precursors for pristine graphene because they can be scaled up to industrial requirement with controllable properties. , However, the lattice structure of GO is more complex than graphene obtained via mechanical exfoliation or chemical vapor deposition (CVD) due to the abundant defects, including oxygen-containing groups and lattice vacancies. This results in different chemical and physical properties in GO and RGO. − On the other hand, RGO has properties that lie between GO and graphene. As a result, the interpretation of Raman spectra of GO and RGO is more complicated than that of other carbon nanomaterials .…”

Enhancing Structural Properties and Performance of Graphene-Based Devices Using Self-Assembled HMDS Monolayers

“…The values of n D and L D observed after HMDS treatment are typical values reported in CVD pristine graphene. 49,50 The reduction of disorder in graphene after HMDS treatment indicates that HMDS acts as a protective layer for graphene that reduces damage during the fabrication process. Reductions of damage are observed for both rf and dc sputtering and different films, as shown in Figure S3 (see the Supporting Information).…”