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Jinshui Miao, Zhihao Xu, Li Qing, Arthur Bowman, Suoming Zhang, Weida Hu, Zhixian Zhou, Chuan Wang
Van der Waals heterojunctions using 2D semiconducting materials could overcome the defect issues included by lattice mismatch in conventional epitaxially-grown heterojunctions with bulk materials and could enable a much wider palette for choice of materials and more sophisticated device design. Such 2D heterojunction devices are of great interest for important functional devices such as diodes, bipolar junction transistors, light-emitting diodes, and photodetectors. In this paper, we demonstrate a truly vertical p-n heterojunction diode built from 2D semiconductors (MoS2 and BP) and compare its performance against conventional lateral 2D heterojunction devices...
September 19, 2017: ACS Nano
Juan Xiang, Taeseup Song
Multicomponent MoS2/Co9S8/C hollow nanocubes were developed by the one-pot solvothermal method and a subsequent calcination process. Benefitting from the merits of hollow structures, the highly-conductive carbon matrix and the buffering effect provided by uniformly-mixed MoS2 and Co9S8, the MoS2/Co9S8/C anode shows high capacity and rate capability as the anode of sodium-ion batteries.
September 19, 2017: Chemical Communications: Chem Comm
Mahfujur Rahaman, Raul D Rodriguez, Gerd Plechinger, Stefan Moras, Christian Schüller, Tobias Korn, Dietrich R T Zahn
Tip-enhanced Raman spectroscopy (TERS) has been rapidly improved over the last decade and opened up opportunities to study phonon properties of materials at the nanometer scale. In this contribution we report on tip-enhanced Raman spectroscopy (TERS) of an ultra-thin MoS2 flake on a nanostructured Au on silicon surface forming a two-dimensional (2D) crystal/plasmonic heterostructure. Au nanostructures (shaped in triangles) are prepared by nanosphere lithography and then MoS2 is mechanically exfoliated on top of them...
September 19, 2017: Nano Letters
Xuying Yin, Ya Yan, Mao Miao, Ke Zhan, Pingwei Li, Junhe Yang, Bin Zhao, Bao Yu Xia
Hydrogen with high purity produced by water splitting is considered as one of the most promising technology to replace the traditional fossil fuels. Developing highly efficient electrocatalysts towards hydrogen evolution is vital for the realization of H2 generation in large scale. With assistance of glycerol, we report herein a facile solvothermal process to synthesize edge-rich ultrathin MoS2/RGO composites. The introduction of glycerol plays an important role in the formation of such an interesting structure...
September 19, 2017: Chemistry: a European Journal
Nengjie Huo, Gerasimos Konstantatos
Two-dimensional transition metal dichalcogenide-based photodetectors have demonstrated potential for the next generation of 2-dimensional optoelectronics. However, to date, their sensitivity has not been superior to that of other technologies. Here we report an ultrasensitive two-dimensional photodetector employing an in-plane phototransistor with an out-of-plane vertical MoS2 p-n junction as a sensitizing scheme. The vertical built-in field is introduced for the first time in the transport channel of MoS2 phototransistors by facile chemical surface doping, which separates the photo-excited carriers efficiently and produces a photoconductive gain of >10(5) electrons per photon, external quantum efficiency greater than 10%, responsivity of 7 × 10(4) A W(-1), and a time response on the order of tens of ms...
September 18, 2017: Nature Communications
Hyeokshin Kwon, Kiyoung Lee, Jinseong Heo, Youngtek Oh, Hyangsook Lee, Samudrala Appalakondaiah, Wonhee Ko, Hyo Won Kim, Jin-Wook Jung, Hwansoo Suh, Hongki Min, Insu Jeon, Euyheon Hwang, Sungwoo Hwang
Despite recent efforts for the development of transition-metal-dichalcogenide-based high-performance thin-film transistors, device performance has not improved much, mainly because of the high contact resistance at the interface between the 2D semiconductor and the metal electrode. Edge contact has been proposed for the fabrication of a high-quality electrical contact; however, the complete electronic properties for the contact resistance have not been elucidated in detail. Using the scanning tunneling microscopy/spectroscopy and scanning transmission electron microscopy techniques, the edge contact, as well as the lateral boundary between the 2D semiconducting layer and the metalized interfacial layer, are investigated, and their electronic properties and the energy band profile across the boundary are shown...
September 18, 2017: Advanced Materials
Alexander Kerelsky, Ankur Nipane, Drew Edelberg, Dennis Wang, Xiaodong Zhou, Abdollah Motmaendadgar, Hui Gao, Saien Xie, Kibum Kang, Jiwoong Park, James Teherani, Abhay Pasupathy
High quality electrical contact to semiconducting transition metal dichalcogenides (TMDCs) such as MoS2 is key to unlocking their unique electronic and optoelectronic properties for fundamental research and device applications. Despite extensive experimental and theoretical efforts reliable ohmic contact to doped TMDCs remains elusive and would benefit from a better understanding of the underlying physics of the metal-TMDC interface. Here we present measurements of the atomic-scale energy band diagram of junctions between various metals and heavily doped monolayer MoS2 using ultrahigh vacuum scanning tunneling microscopy (UHV-STM)...
September 20, 2017: Nano Letters
Zheguan Lin, Jinjin Lin, Lingting Huang, Xiaoyan Zhang, Ying Wang, Zizhong Zhang, Huaxiang Lin, Xuxu Wang
Developing a heterostructure on the surface of a "sandwich" structure semiconductor is essential for full utilization of its heterojunction function and hence for designing efficient solar energy conversion systems. Here, we show that 2D-2D MoS2/MnSb2S4 heterostructure composites are designed for the first time and successfully synthesized by a simple in situ calcination pathway. Under visible light irradiation, the ca. 3.3 wt% MoS2/MnSb2S4 samples exhibited the highest activity for H2 evolution, which was 7...
September 18, 2017: Nanoscale
Helio Ribeiro, João Paulo Campos Trigueiro, Wellington M Silva, Cristiano F Woellner, Peter Samora Owuor, Alin Cristian Chipara, Magnovaldo Carvalho Lopes, Chandra Sekhar Tiwary, Jairo José Pedrotti, Rodrigo Villegas Salvatierra, James M Tour, Nitin Chopra, Ihab N Odeh, Glaura Silva, Pulickel M Ajayan
Two-dimensional (2D) nanomaterials as molybdenum disulfide (MoS2), hexagonal boron nitride (h-BN), and the hybrid (MoS2/h-BN) were employed as fillers to improve the physical properties of epoxy composites. Nanocomposites were produced in different concentrations and studied in their microstructure, mechanical and thermal properties. The hybrid 2D mixture imparted efficient reinforcement to the epoxy leading to increases of up to 95% in tensile strength, 60% in ultimate strain and 58% in Young's modulus. Moreover, an enhancement of 203% in thermal conductivity was achieved for the hybrid composite as compared to neat polymer...
September 18, 2017: ACS Applied Materials & Interfaces
Yudong Xue, Govindhan Maduraiveeran, Mingyong Wang, Shili Zheng, Yi Zhang, Wei Jin
Owing to the extensive applications of hydrogen peroxide (H2O2) in biological, environmental and chemical engineering, it is of great importance to investigate sensitive and selective sensing platform towards the detection of H2O2. Herein, oxygen-implanted MoS2 nanoparticles decorated graphene nanocomposite is synthesized via a facile one-pot solvothermal method for the sensitive detection of H2O2 in alkaline media. The structure and morphology of the MoS2/graphene nanocomposites were systematically characterized, showing that Mo-O bonds are formed and oxygen is implanted into the crystal structure in the nanocomposite...
January 1, 2018: Talanta
Mohammad Heiranian, Yanbin Wu, Narayana R Aluru
Understanding the interaction between water and molybdenum disulfide (MoS2) is of crucial importance to investigate the physics of various applications involving MoS2 and water interfaces. An accurate force field is required to describe water and MoS2 interactions. In this work, water-MoS2 force field parameters are derived using the high-accuracy random phase approximation (RPA) method and validated by comparing to experiments. The parameters obtained from the RPA method result in water-MoS2 interface properties (solid-liquid work of adhesion) in good comparison to the experimental measurements...
September 14, 2017: Journal of Chemical Physics
Anja Förster, Sibylle Gemming, Gotthard Seifert, David Tomanek
Using ab initio density functional theory calculations, we characterize changes in the electronic structure of MoS2 monolayers introduced by missing or additional adsorbed sulfur atoms. We furthermore identify the chemical and electronic function of substances that have been reported to reduce the adverse effect of sulfur vacancies in quenching photoluminescence and reducing electronic conductance. We find that thiol-group containing molecules adsorbed at vacancy sites may re-insert missing sulfur atoms. In presence of additional adsorbed sulfur atoms, thiols may form disulfides on the MoS2 surface to mitigate the adverse effect of defects...
September 15, 2017: ACS Nano
Wenting Zhang, Yue Lin, Qi Wang, Weijie Li, Zhifeng Wang, Jiangluqi Song, Xiaodong Li, Lijie Zhang, Lixin Zhu, XiaoLiang Xu
Guided by the hexagonal lattice symmetry, triangle and hexagon are the most basic morphological unit for the two-dimensional (2D) transition metal dichalcogenides (TMDs) synthesized by chemical vapor deposition (CVD). Also, it is widely acknowledged that these units start from the single nucleation site and then grow epitaxially. Accordingly, the triangular monolayer (ML) samples are generally considered as single crystals. Here, we report a 2D core-shell growth mode in the CVD process for ML-MoS2, which leads to one kind of "pseudo" single crystal triangles containing triangular outline grain boundaries (TO-GBs)...
September 15, 2017: ACS Nano
Massimo Macucci, Gerry Tambellini, Dmitry Ovchinnikov, Andras Kis, Giuseppe Iannaccone, Gianluca Fiori
We present an experimental investigation of slow transients in the gate and drain currents of MoS2-based transistors. We focus on the measurement of both the gate and drain currents and, from the comparative analysis of the current transients, we conclude that there are at least two independent trapping mechanisms: trapping of charges in the silicon oxide substrate, occurring with time constants of the order of tens of seconds and involving charge motion orthogonal to the MoS2 sheet, and trapping at the channel surface, which occurs with much longer time constants, in particular when the device is in a vacuum...
September 14, 2017: Scientific Reports
Xianchong Miao, Ningning Xuan, Qi Liu, Weishu Wu, Hanqi Liu, Zhengzong Sun, Minbiao Ji
Two-dimensional (2D) materials have attracted broad research interests across various nonlinear optical (NLO) studies, including nonlinear photoluminescence (NPL), second harmonic generation (SHG), transient absorption (TA), and etc. These studies have unveiled important features and information of 2D materials, such as in grain boundaries, defects and crystal orientations. However, as most researches focused on the intrinsic NLO processes, little attention has been paid to the substrates underneath. Here, we discovered that the NLO signal depends significantly on the thickness of SiO2 in SiO2/Si substrates...
September 14, 2017: ACS Applied Materials & Interfaces
Cecil N M Ouma, Sobhit Singh, Kingsley O Obodo, George O Amolo, Aldo H Romero
The electronic, magnetic and optical properties of lanthanide substitutional doping (∼2% concentration) on the MoS2 monolayer have been investigated within the density functional theory formalism together with the Hubbard correction (DFT+U). The dopants investigated include Ce, Eu, Gd, Lu and Tm. The calculated dopant substitutional energies under both Mo-rich and S-rich conditions suggest that it is possible to experimentally realize the lanthanide doped MoS2 monolayer systems. The Eu, Gd and Tm dopants induce strong magnetization in the host lattice...
September 13, 2017: Physical Chemistry Chemical Physics: PCCP
Guichong Jia, Huanwen Wang, Dongliang Chao, Haiyong He, Nguyen Huy Tiep, Yongqi Zhang, Zheng Zhang, Hongjin Fan
Two-dimensional (2D) transition metal dichalcogenides are widely studied as anode materials for metal ion batteries. This application requires high electric conductivity which can be achieved by forming composites with conductive carbon. In this work, we demonstrate the creation of nanospheres composed of Mo-based thin nanosheets (MoS2, MoSe2 and Mo2C) uniform embedded within a N-doped carbon matrix. Using MoSe2/N-doped carbon nanospheres as example, we investigate in deails the electrochemical property in Na ion storage and reveal the advantage over previously reported MoSe2 electrodes (higher capacity and improved capacity retention up to 500 cycles)...
September 13, 2017: Nanotechnology
Jinseok Baek, Tomokazu Umeyama, Wookjin Choi, Yusuke Tsutsui, Hiroki Yamada, Shu Seki, Hiroshi Imahori
Composite films consisting of C60 and well-exfoliated nanosheets of transition metal dichalcogenides (TMDs), i.e., MoS2 or WS2, with a bulk heterojunction structure were facilely fabricated onto a semiconducting SnO2 electrode via a two-step methodology; self-assembly into their composite aggregates by injecting poor solvent into good solvent with the dispersion and subsequent electrophoretic deposition. Photoexcitation of the composites on SnO2 exhibited enhanced transient conductivities in comparison with single components of TMDs or C60, demonstrating that the bulk heterojunction nanostructure of TMD and C60 promoted the charge separation (CS)...
September 13, 2017: Chemistry: a European Journal
Yuan Sun, Wei Zhong, Yuanqi Wang, Xiaobing Xu, Tingting Wang, Liqian Wu, Youwei Du
It is widely recognized that constructing multiple interface structures for enhanced interface polarization is beneficial to microwave absorption. Here, we report our work of achieving excellent microwave absorption performance and controlling better-defined interfaces in vertically stacked of 2D MoS2 with other dimensional building blocks. The optimal reflection loss and effective absorbing bandwidth (reflection loss <-10 dB) of several mixed-dimensional van der Waals heterostructures are that: (i) for 2-0 type (2D MoS2 / 0D Ni nanoparticles), -19...
September 13, 2017: ACS Applied Materials & Interfaces
Yuechao Tang, Xurui Zhang, Phillip Choi, Qingxia Liu, Zhenghe Xu
Molybdenum disulfide (MoS2) has been receiving increasing attention in scientific research due to its unique properties. Up to now, several techniques have been developed to prepare exfoliated nano-size MoS2 dispersions to facilitate its applications. To improve its desired performance, as-prepared MoS2 dispersion needs further appropriate modification by polymers. Thus, understanding polymer-MoS2 interaction is of great scientific importance and practical interests. Here, results on molecular interactions of a biocompatible stimuli-responsive copolymer with basal plane surface of MoS2 determined using Single Molecule Force Spectroscopy (SMFS) are reported...
September 12, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
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