Search query: MoS2

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abstract: Two dimensional materials are attractive for use in next generation nanoelectronic devices because, compared to one dimensional materials, it is relatively easy to fabricate complex structures from them. The most widely studied two dimensional material is graphene, both because of its rich physics and its high mobility. However, pristine graphene does not have a bandgap, a property that is essential for many applications, including transistors. Engineering a graphene bandgap increases fabrication complexity and either reduces mobilities to the level of strained silicon films or requires high voltages. Although single layers of MoS(2) have a large intrinsic bandgap of 1.8 eV (ref. 16) previously reported mobilities in the 0.5 3 cm(2) V( 1) s( 1) range are too low for practical devices. Here, we use a halfnium oxide gate dielectric to demonstrate a room temperature single layer MoS(2) mobility of at least 200 cm(2) V( 1) s( 1) similar to that of graphene nanoribbons, and demonstrate transistors with room temperature current on/off ratios of 1 x 10(8) and ultralow standby power dissipation. Because monolayer MoS(2) has a direct bandgap, it can be used to construct interband tunnel FETs, which offer lower power consumption than classical transistors. Monolayer MoS(2) could also complement graphene in applications that require thin transparent semiconductors, such as optoelectronics and energy harvesting.
author_names: Branimir Radisavljevic

Aleksandra Radenovic

Jacopo Brivio

Valentina Giacometti

Andras Kis
title: Single layer MoS2 transistors.
venue: Nature nanotechnology
year: 2011

abstract: Two dimensional materials are an emerging class of new materials with a wide range of electrical properties and potential practical applications. Although graphene is the most well studied two dimensional material, single layers of other materials, such as insulating BN (ref. 2) and semiconducting MoS2 (refs 3, 4) or WSe2 (refs 5, 6) are gaining increasing attention as promising gate insulators and channel materials for field effect transistors. Because monolayer MoS2 is a direct bandgap semiconductor due to quantum mechanical confinement, it could be suitable for applications in optoelectronic devices where the direct bandgap would allow a high absorption coefficient and efficient electron hole pair generation under photoexcitation. Here, we demonstrate ultrasensitive monolayer MoS2 phototransistors with improved device mobility and ON current. Our devices show a maximum external photoresponsivity of 880 A W( 1) at a wavelength of 561 nm and a photoresponse in the 400 680 nm range. With recent developments in large scale production techniques such as liquid scale exfoliation and chemical vapour deposition like growth, MoS2 shows important potential for applications in MoS2 based integrated optoelectronic circuits, light sensing, biomedical imaging, video recording and spectroscopy.
author_names: Oriol Lopez-Sanchez

Dominik S Lembke

M Kayci

Aleksandra Radenovic

Andras Kis
title: Ultrasensitive photodetectors based on monolayer MoS2.
venue: Nature nanotechnology
year: 2013

abstract: Novel physical phenomena can emerge in low dimensional nanomaterials. Bulk MoS(2) a prototypical metal dichalcogenide, is an indirect bandgap semiconductor with negligible photoluminescence. When the MoS(2) crystal is thinned to monolayer, however, a strong photoluminescence emerges, indicating an indirect to direct bandgap transition in this d electron system. This observation shows that quantum confinement in layered d electron materials like MoS(2) provides new opportunities for engineering the electronic structure of matter at the nanoscale.
author_names: Andrea Splendiani

Liang Sun

Yuanbo Zhang

Tianshu Li

Jonghwan Kim

Chi Yung Chim

Giulia Galli

Feng Wang
title: Emerging photoluminescence in monolayer MoS2.
venue: Nano letters
year: 2010

abstract: Abstract Designing and constructing bifunctional electrocatalysts is vital for water splitting. Particularly, the rational interface engineering can effectively modify the active sites and promote the electronic transfer, leading to the improved splitting efficiency. Herein, free standing and defect rich heterogeneous MoS2/NiS2 nanosheets for overall water splitting are designed. The abundant heterogeneous interfaces in MoS2/NiS2 can not only provide rich electroactive sites but also facilitate the electron transfer, which further cooperate synergistically toward electrocatalytic reactions. Consequently, the optimal MoS2/NiS2 nanosheets show the enhanced electrocatalytic performances as bifunctional electrocatalysts for overall water splitting. This study may open up a new route for rationally constructing heterogeneous interfaces to maximize their electrochemical performances, which may help to accelerate the development of nonprecious electrocatalysts for overall water splitting.
author_names: Jinghuang Lin

Pengcheng Wang

Haohan Wang

Chun Li

Xiaoqing Si

Junlei Qi

Jian Cao

Zhengxiang Zhong

Weidong Fei

Ji-cai Feng
title: Defect Rich Heterogeneous MoS2/NiS2 Nanosheets Electrocatalysts for Efficient Overall Water Splitting
venue: Advanced science
year: 2019

abstract: Abstract Although graphitic carbon nitride (g C3N4) is an attractive photocatalyst for solar H2 generation, the preparation of g C3N4 nanosheets via a "green" and simple method as well as the construction of highly efficient g C3N4 based photocatalysts are still challenges. In this study, g C3N4 nanosheets prepared by a simple probe sonication assisted liquid exfoliation method were used to construct 2D 2D MoS2/g C3N4 photocatalyst for photocatalytic H2 production. The 2D 2D MoS2/g C3N4 photocatalyst containing 0.75% MoS2 showed the highest H2 evolution rate of 1155 mmol*h 1*g 1 with an apparent quantum yield of 6.8% at 420 nm monochromatic light, which is much higher than that of the optimized 0D 2D Pt/g C3N4 photocatalyst. The high photocatalytic H2 production activity of 2D 2D MoS2/g C3N4 photocatalyst can be attributed to the large surface area and the formed 2D interfaces between MoS2 and g C3N4 nanosheets. As demonstrated by photoluminescence quenching and time resolved fluorescence decay studies, the 2D interfaces can accelerate the photoinduced charge transfer, resulting in the high photocatalytic H2 production performance. This study provides a new strategy in developing highly efficient g C3N4 based photocatalysts for H2 production via using 2D nanojunction as a bridge to promote the photoinduced charge separation and transfer.
author_names: Yongjun Yuan

Zhi-Kai Shen

Shiting Wu

Yibing Su

Lang Pei

Zhen-guo Ji

Mingye Ding

Wangfeng Bai

Yifan Chen

Zhen-Tao Yu

Zhi-gang Zou
title: Liquid exfoliation of g C3N4 nanosheets to construct 2D 2D MoS2/g C3N4 photocatalyst for enhanced photocatalytic H2 production activity
venue: Applied Catalysis B: Environmental
year: 2019

abstract: A novel approach to effectively suppress the "polysulfide shuttle" in Li S batteries is presented by designing a freestanding, three dimensional graphene/1T MoS2 (3DG/TM) heterostructure with highly efficient electrocatalysis properties for lithium polysulfides (LiPSs) The 3DG/TM heterostructure is constructed by few layered graphene nanosheets sandwiched by hydrophilic, metallic, few layered 1T MoS2 nanosheets with abundant active sites. The porous 3D structure and the hydrophilic feature of 1T MoS2 are beneficial for electrolyte penetration and Li ion transfer, and the high conductivities of both graphene and the 1T MoS2 nanosheets facilitate electron transfer. These merits lead to a high electrocatalytic efficiency for LiPSs due to excellent ion/electron transfer and the presence of sufficient electrocatalytic active sites. Therefore, the cells with 3DG/TM exhibit outstanding electrochemical performance, with a high reversible discharge capacity of 1181 mA h g 1 and a capacity retention of 96.3% after 200 cycles. The electrocatalysis mechanism of LiPSs is further experimentally and theoretically revealed, which provides new insights and opportunities to develop advanced Li S batteries with highly efficient electrocatalysts for LiPS conversion.
author_names: Jiarui He

Gregor Hartmann

Myungsuk Lee

Gyeong S Hwang

Yuanfu Chen

Arumugam Manthiram
title: Freestanding 1T MoS2/graphene heterostructures as a highly efficient electrocatalyst for lithium polysulfides in Li S batteries
year: 2019

abstract: Abstract Exposing the highly active facets and hybridizing the photocatalyst with appropriate cocatalysts with right placement have been regarded as a powerful approach to high performance photocatalysts. Herein, TiO2 nanosheets (NSs) are in situ grown on highly conductive Ti3C2 MXene and then MoS2 NSs are deposited on the (101) facets of TiO2 NSs with mainly exposed high active (001) facets through a two step hydrothermal method. And a unique 2D 2D 2D structure of Ti3C2@TiO2@MoS2 composite is achieved. With an optimized MoS2 loading amounts (15 wt% the Ti3C2@TiO2@MoS2 composite shows a remarkable enhancement in the photocatalytic H2 evolution reaction compared with Ti3C2@TiO2 composite and TiO2 NS. It also shows good stability under the reaction condition. This arises from: (i) the in situ growth of TiO2 NSs construct strong interfacial contact with excellent electronic conductivity of Ti3C2, which facilitates the separation of carriers; (ii) the coexposed (101) and (001) facets can form a surface heterojunction within single TiO2 NS, which is beneficial for the transfer and separation of charge carriers; and (iii) the MoS2 NSs are deposited on the electrons rich (101) facets of TiO2 NSs, which not only effectively reduces the charge carriers recombination rate by capturing photoelectrons, but also makes TiO2 NSs expose more highly active (001) facets to afford high efficiency photogeneration of electron hole pairs.
author_names: Yujie Li

Zhaohua Yin

Guanrui Ji

Zhang Liang

Yanjun Xue

Yichen Guo

Jian Tian

Xinzhen Wang

Hongzhi Cui
title: 2D/2D/2D heterojunction of Ti3C2 MXene/MoS2 nanosheets/TiO2 nanosheets with exposed (001) facets toward enhanced photocatalytic hydrogen production activity
venue: Applied Catalysis B: Environmental
year: 2019

abstract: Low dimensional materials have been examined as electrocatalysts for the hydrogen evolution reaction (HER) Among them, two dimensional transition metal dichalcogenides (2D TMDs) such as MoS2 have been identified as potential candidates. However, the performance of TMDs toward HER in both acidic and basic media remains inferior to that of noble metals such as Pt and its alloys. This calls for investigating the influence of controlled defect engineering of 2D TMDs on their performance toward hydrogen production. Here, we explored the HER activity from defective multilayered MoS2 over a large range of surface S vacancy concentrations up to 90% Amorphous MoS2 and 2H MoS2 with ultrarich S vacancies demonstrated the highest HER performance in acid and basic electrolytes, respectively. We also report that the HER performance from multilayered MoS2 can be divided into two domains corresponding to "point defects" at low concentrations of surface S vacancies (Stage 1) and large regions of undercoordinated Mo atoms for high concentrations of surface S vacancies (Stage 2) The highest performance is obtained for Stage 2 in the presence of undercoordinated Mo atoms with a TOF of ~2 s 1 at an overpotential of 160 mV in 0.1 M KOH which compares favorably to the best results in the literature. Overall, our work provides deeper insight on the HER mechanism from defected MoS2 and provides guidance for the development of defect engineered TMD based electrocatalysts.
author_names: Lei Li

Zhao-Xian Qin

Lucie Ries

Song Hong

Thierry Michel

Jieun Yang

Chrystelle Salameh

Mikhael Bechelany

Philippe Miele

Daniel Kaplan

Manish Chhowalla

Damien Voiry
title: Role of Sulfur Vacancies and Undercoordinated Mo Regions in MoS2 Nanosheets toward the Evolution of Hydrogen.
venue: ACS nano
year: 2019

abstract: We show that inversion symmetry breaking together with spin orbit coupling leads to coupled spin and valley physics in monolayers of MoS2 and other group VI dichalcogenides, making possible controls of spin and valley in these 2D materials. The spin valley coupling at the valence band edges suppresses spin and valley relaxation, as flip of each index alone is forbidden by the valley contrasting spin splitting. Valley Hall and spin Hall effects coexist in both electron doped and hole doped systems. Optical interband transitions have frequency dependent polarization selection rules which allow selective photoexcitation of carriers with various combination of valley and spin indices. Photoinduced spin Hall and valley Hall effects can generate long lived spin and valley accumulations on sample boundaries. The physics discussed here provides a route towards the integration of valleytronics and spintronics in multivalley materials with strong spin orbit coupling and inversion symmetry breaking.
author_names: Di Xiao

Gui-Bin Liu

Wanxiang Feng

Xiaodong Xu

Wang Yao
title: Coupled spin and valley physics in monolayers of MoS2 and other group VI dichalcogenides.
venue: Physical review letters
year: 2012

abstract: The identification of the active sites in heterogeneous catalysis requires a combination of surface sensitive methods and reactivity studies. We determined the active site for hydrogen evolution, a reaction catalyzed by precious metals, on nanoparticulate molybdenum disulfide (MoS2) by atomically resolving the surface of this catalyst before measuring electrochemical activity in solution. By preparing MoS2 nanoparticles of different sizes, we systematically varied the distribution of surface sites on MoS2 nanoparticles on Au(111) which we quantified with scanning tunneling microscopy. Electrocatalytic activity measurements for hydrogen evolution correlate linearly with the number of edge sites on the MoS2 catalyst.
author_names: Thomas Francisco Jaramillo

Kristina Pilt Jorgensen

Jacob Bonde

Jane Hvolbaek Nielsen

Sebastian Horch

Ib Chorkendorff
title: Identification of Active Edge Sites for Electrochemical H2 Evolution from MoS2 Nanocatalysts
venue: Science
year: 2007