Carrier Control of MoS<sub>2</sub> Nanoflakes by Functional Self-Assembled Monolayers

Yang, Li; Xu, Cheng‐Yan; Hu, PingAn

doi:10.1021/nn402682j

Cited by 220 publications

(269 citation statements)

References 57 publications

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“…1p, the E 1 2g peak of 1L AA-MoS 2 was blue-shifted by 0.8 cm −1 compared to that of pristine 1L MoS 2 , which is different from unchanged E 1 2g peak of 1L MoS 2 on water adlayer [29]. It has been reported that both electron and hole doping will not affect the position of E 1 2g peak [42], and thus this blue shift ARTICLES . .…”

Section: Resultsmentioning

confidence: 85%

The influence of two-dimensional organic adlayer thickness on the ultralow frequency Raman spectra of transition metal dichalcogenide nanosheets

Shi

Liu

et al. 2018

Sci. China Mater.

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Recently, it has been reported that physisorbed adsorbates can be trapped between the bottom surface of twodimensional (2D) materials and supported substrate to form 2D confined films. However, the influence of such 2D confined adsorbates on the properties of 2D materials is rarely explored. Herein, we combined atomic force microscopy (AFM), Kelvin probe force microscopy (KPFM) and Raman spectroscopy especially the ultralow frequency (ULF) Raman spectroscopy to explore the influence of 2D confined organic adlayer thickness on the ULF breathing modes of few-layer MoS 2 and WSe 2 nanosheets. As the thickness of organic adlayers increased, red shift, coexistence of blue and red shifts as well as blue shift of ULF breathing mode was observed. KPFM measurement confirmed the enhanced n-doping and p-doping behaviors of organic adlayers as their thickness increased, respectively. Our results will provide new insights into the interaction between 2D confined adsorbates and bottom surface of 2D nanosheets, which could be useful for modulating properties of 2D materials.

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Section: Resultsmentioning

confidence: 85%

The influence of two-dimensional organic adlayer thickness on the ultralow frequency Raman spectra of transition metal dichalcogenide nanosheets

Shi

Liu

et al. 2018

Sci. China Mater.

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“…The impact of substrates [10,11], the gaseous environment as well as of adsorbates [12][13][14] on the optoelectronic properties of 2D materials have been reported. The atomistic interfaces offer the opportunity of novel route for interfacial engineering of electronic, optical and optoelectronic properties [10,12,15,16].In this letter, we study the effect of photogating in MoS 2 mono-and few-layer flakes by means of Raman spectroscopy. Our observations are consistent with physisorbed environmental molecules acting as molecular gates.…”

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confidence: 99%

Photogating of mono- and few-layer MoS2

Miller

Parzinger

Vernickel

et al. 2015

Applied Physics Letters

126

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We describe a photogating effect in mono-and few-layer MoS2, which allows the control of the charge carrier density by almost two orders of magnitude without electrical contacts. Our Raman studies are consistent with physisorbed environmental molecules, that effectively deplete the intrinsically n-doped charge carrier system via charge transfer, and which can be gradually removed by the exposure to light. This photogating process is reversible and precisely tunable by the light intensity. The photogating efficiency is quantified by comparison with measurements on electrostatically gated MoS2.Two-dimensional layered van-der Waals materials and their heterostructures, particularly the transition metal dichalcogenides (TMDCs) family such as MoS 2 , are of great interest for fundamental research as well as for novel device concepts in the areas of electronic [1,2], optoelectronic [1,[3][4][5], valley-and spintronic [6] as well as solar energy conversion [7] and sensing applications [8]. It has been demonstrated that MoS 2 undergoes a transition from an indirect to a direct bandgap semiconductor by thinning it down to one single layer [3]. The direct gap at the K-point with E gap = 1.9 eV [3] remains almost unaffected by the number of layers. The indirect gap existing in vicinity of the Γ-point decreases in energy for increasing number of layers [3]. In particular, a high absorption of the monolayer of 5-10% in the visible regime [9] makes MoS 2 a promising material for optoelectronic devices such as phototransistors and solar cells. For atomistic thin materials, knowledge about the interaction with the dielectric environment is of great importance. The impact of substrates [10,11], the gaseous environment as well as of adsorbates [12][13][14] on the optoelectronic properties of 2D materials have been reported. The atomistic interfaces offer the opportunity of novel route for interfacial engineering of electronic, optical and optoelectronic properties [10,12,15,16].In this letter, we study the effect of photogating in MoS 2 mono-and few-layer flakes by means of Raman spectroscopy. Our observations are consistent with physisorbed environmental molecules acting as molecular gates. The molecules can be gradually removed from the MoS 2 surface by the exposure to light. We find that the photogating effect facilitates the control of the charge carrier density in MoS 2 by almost two orders of magnitude in pristine flakes without the need for electrical contacts. In general, Raman spectroscopy provides access to various properties of 2D layered materials [17] such as to the number of layers [18,19], to strain [20,21] to the local temperature [22] and to the doping level [23]. The Raman spectrum of MoS 2 includes two prominent firstorder phonon modes, the E 1 2g and the A 1g mode [17]. The E 1 2g mode is an in-plane mode, i.e. the atoms are oscillating parallel to the basal plane of the van-der Waals coupled crystal layers. The A 1g mode is an out-of plane oscillation, where the sulfur atoms are moving in opposite directions...

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“…The built-in electric field induces an additional charge redistribution across the interface, which modifies the surface electronic properties of condensed matter used as the substrate. To date, the effects of SAM formation on the magnetism, 15,16,1922 conductiv-ity, 9,10,18,23,24 and superconductivity 2527 have been reported by several research groups.…”

Section: Introductionmentioning

confidence: 99%

A New Photo-Control Method for Organic–Inorganic Interface Dipoles and Its Application to Photo-Controllable Molecular Devices

Suda

2017

Bulletin of the Chemical Society of Japan

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The ability to manipulate the behavior of electrons at organicinorganic interfaces is of crucial importance in the development of future molecular devices. It has been shown that interface dipoles, created by the chemisorption of a selfassembled organic monolayer (SAM) on a solid surface, induce carrier injection effects. This means that the interface electronic properties can be manipulated by designing the molecular dipoles and arrangements in the SAMs. In this study, a novel strategy to photo-control molecular dipoles through the use of photochromic SAMs is proposed, and a number of photocontrollable molecular devices have been developed based on this strategy. This account provides a review of the basic concept of the photo-control of interface dipoles and the recent advances in the development of photo-controllable molecular devices.

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Carrier Control of MoS₂ Nanoflakes by Functional Self-Assembled Monolayers

Cited by 220 publications

References 57 publications

The influence of two-dimensional organic adlayer thickness on the ultralow frequency Raman spectra of transition metal dichalcogenide nanosheets

The influence of two-dimensional organic adlayer thickness on the ultralow frequency Raman spectra of transition metal dichalcogenide nanosheets

Photogating of mono- and few-layer MoS2

A New Photo-Control Method for Organic–Inorganic Interface Dipoles and Its Application to Photo-Controllable Molecular Devices

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Carrier Control of MoS2 Nanoflakes by Functional Self-Assembled Monolayers

Cited by 220 publications

References 57 publications

The influence of two-dimensional organic adlayer thickness on the ultralow frequency Raman spectra of transition metal dichalcogenide nanosheets

The influence of two-dimensional organic adlayer thickness on the ultralow frequency Raman spectra of transition metal dichalcogenide nanosheets

Photogating of mono- and few-layer MoS2

A New Photo-Control Method for Organic–Inorganic Interface Dipoles and Its Application to Photo-Controllable Molecular Devices

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Product

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Carrier Control of MoS₂ Nanoflakes by Functional Self-Assembled Monolayers