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Yu-Chuan Lin, Kursti DeLello, Hai-Tian Zhang, Kehao Zhang, Zhong Lin, Mauricio Terrones, Roman Engel-Herbert, Joshua A Robinson
Integrating a phase transition material with two-dimensional semiconductors can provide a route towards tunable opto-electronic metamaterials. Here, we integrate monolayer transition metal dichalcogenides with vanadium dioxide (VO2) thin films grown via molecular beam epitaxy to form a 2D/3D heterostructure. Vanadium dioxide undergoes an insulator-to-metal transition at 60-70 °C, which changes the band alignment between MoS2 and VO2 from a semiconductor-insulator junction to a semiconductor-metal junction...
October 25, 2016: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Nirpendra Singh, Udo Schwingenschlögl
Realization of permanent valley polarization in Cr-doped monolayer MoS2 is found to be unfeasible because of extended moment formation. Introduction of an additional hole is suggested as a viable solution. V-doped monolayer MoS2 is demonstrated to sustain permanent valley polarization and therefore can serve as a prototype material for valleytronics.
October 24, 2016: Advanced Materials
Mehwish Naz, Toby Hallam, Nina C Berner, Niall McEvoy, Riley Gatensby, John B McManus, Zareen Akhter, Georg S Duesberg
We report on 2H-2H'/1T phase conversion of MoS2 and MoSe2 polycrystalline films grown by thermally assisted conversion. The structural conversion of the transition metal dichalcogenides was successfully carried out by organolithium treatment on chip. As a result we obtained a new 2H-2H'/1T co-phase system of the TMDs thin films which was verified by Raman spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The conversion was successfully carried to on selected areas yielding a lateral heterostructure between the pristine 2H phase and the 2H'/1T co-phase regions...
October 24, 2016: ACS Applied Materials & Interfaces
Hyung-Youl Park, Sreekantha Reddy Dugasani, Dong-Ho Kang, Gwangwe Yoo, Jinok Kim, Bramaramba Gnapareddy, Jaeho Jeon, Minwoo Kim, Young Jae Song, Sungjoo Lee, Jonggon Heo, Young Jin Jeon, Sung Ha Park, Jin-Hong Park
Here, we report a high performance biosensor based on (i) a Cu(2+)-DNA/MoS2 hybrid structure and (ii) a field effect transistor, which we refer to as a bio-FET, presenting a high sensitivity of 1.7 × 10(3) A/A. This high sensitivity was achieved by using a DNA nanostructure with copper ions (Cu(2+)) that induced a positive polarity in the DNA (receptor). This strategy improved the detecting ability for doxorubicin-like molecules (target) that have a negative polarity. Very short distance between the biomolecules and the sensor surface was obtained without using a dielectric layer, contributing to the high sensitivity...
October 24, 2016: Scientific Reports
Chong-Rong Wu, Xiang-Rui Chang, Tung-Wei Chu, Hsuan-An Chen, Chao-Hsin Wu, Shih-Yen Lin
A 9-layer WS2/MoS2 hetero-structure is established on a sapphire substrate after sequential growth of large-area and uniform 5- and 4- layer MoS2 and WS2 films by using sulfurization of pre-deposited 1.0 nm Molybdenum (Mo) and Tungsten (W), respectively. By using the results obtained from the ultraviolet photoelectron spectroscopy and the absorption spectrum measurements of the standalone MoS2 and WS2 samples, a type-II band alignment is predicated for the WS2/MoS2 hetero-structure. Increasing drain currents and enhanced field-effect mobility value of the transistor fabricated on the hetero-structure suggested that a channel with higher electron concentration compared with the standalone MoS2 transistor channel is obtained with electron injection from WS2 to MoS2 under thermal equilibrium...
October 20, 2016: Nano Letters
Xuexia He, WaiLeong Chow, Fucai Liu, BengKang Tay, Zheng Liu
2D transition metal dichalcogenides are promising channel materials for the next-generation electronic device. Here, vertically 2D heterostructures, so called van der Waals solids, are constructed using inorganic molybdenum sulfide (MoS2 ) few layers and organic crystal - 5,6,11,12-tetraphenylnaphthacene (rubrene). In this work, ambipolar field-effect transistors are successfully achieved based on MoS2 and rubrene crystals with the well balanced electron and hole mobilities of 1.27 and 0.36 cm(2) V(-1) s(-1) , respectively...
October 20, 2016: Small
Stéphane Cadot, Olivier Renault, Mathieu Frégnaux, Denis Rouchon, Emmanuel Nolot, Kai Szeto, Chloé Thieuleux, Laurent Veyre, Hanako Okuno, François Martin, Elsje Alessandra Quadrelli
The lack of scalable-methods for the growth of 2D MoS2 crystals, an identified emerging material with applications ranging from electronics to energy storage, is a current bottleneck against its large-scale deployment. We report here a two-step ALD route with new organometallic precursors, Mo(NMe2)4 and 1,2-ethanedithiol (HS(CH2)2SH) which consists in the layer-by-layer deposition of an amorphous surface Mo(iv) thiolate at 50 °C, followed by a subsequent annealing at higher temperature leading to ultra-thin MoS2 nanocrystals (∼20 nm-large) in the 1-2 monolayer range...
October 20, 2016: Nanoscale
Zhe Lv, Nasir Mahmood, Muhammad Tahir, Lun Pan, Xiangwen Zhang, Ji-Jun Zou
Transition metal dichalcogenides (TMDs) are emerging as promising materials, particularly for electrochemical and photochemical catalytic applications, and among them molybdenum sulfides have received tremendous attention due to their novel electronic and optoelectronic characteristics. Several review articles have summarized the recent progress on TMDs but no critical and systematic summary exists about the nanoscale fabrication of MoS2 with different dimensional morphologies. In this review article, first we will summarize the recent progress on the morphological tuning and structural evolution of MoS2 from zero-dimension (0D) to 3D...
October 20, 2016: Nanoscale
Tan Xing, Srikanth Mateti, Lu Hua Li, Fengxian Ma, Aijun Du, Yury Gogotsi, Ying Chen
Two-dimensional (2D) materials can be produced using ball milling with the help of liquid surfactants or solid exfoliation agents, as ball milling of bulk precursor materials usually produces nanosized particles because of high-energy impacts. Post-milling treatment is thus needed to purify the nanosheets. We show here that nanosheets of graphene, BN, and MoS2 can be produced by ball milling of their bulk crystals in the presence of ammonia or a hydrocarbon ethylene gas and the obtained nanosheets remain flat and maintain their single-crystalline structure with low defects density even after a long period of time; post-milling treatment is not needed...
October 19, 2016: Scientific Reports
Honglin Li, Ke Yu, Zheng Tang, Zi-Qiang Zhu
Electrochemically splitting water for hydrogen evolution has attracted a lot attention and developed as a promising approach to produce hydrogen energy. Searching for high-activity and economical electrocatalysts to replace Pt-based catalysts remains a great challenge. In this paper, we reported a concise and effective strategy to fabricate the novel MoWS2 composite for using as the electrocatalyst through hydrothermal method for the first time. The final obtained MoWS2 composite demonstrated a well-defined hierarchical structure and that the densely stacked nanopetals act as the active sites to participate the corresponding hydrogen evolution reaction (HER) processes...
October 18, 2016: ACS Applied Materials & Interfaces
Hohyeon Lee, Haemin Kim, Thang Phan Nguyen, Jin Ho Chang, Soo Young Kim, Hyuncheol Kim, Eunah Kang
Photoacoustic activity is the generation of an ultrasonic signal via thermal expansion or bubble formation, stimulated by laser irradiation. Photoacoustic nanoplatforms have recently gained focus for application in bio-electric interfaces. Various photoacoustic material types have been evaluated, including gold nanoparticles, semiconductive π-conjugating polymers (SP), etc. In this study, surfactant-free methoxy-polyethylene glycol-co-polypyrrole copolymer (mPEG-co-PPyr) nanoparticles (NPs) and mPEG-co-PPyr NP/molybdenum disulfide (mPEG-co-PPyr/MoS2) nanocomposites (NCs) were prepared and their photoacoustic activity was demonstrated...
October 18, 2016: ACS Applied Materials & Interfaces
Jiong Zhao, Honggi Nam, Thuc Hue Ly, Seok Joon Yun, Sera Kim, Suyeon Cho, Heejun Yang, Young Hee Lee
Defects in bulk crystals can be classified into vacancies, interstitials, grain boundaries, stacking faults, dislocations, and so forth. In particular, the vacancy in semiconductors is a primary defect that governs electrical transport. Concentration of vacancies depends mainly on the growth conditions. Individual vacancies instead of aggregated vacancies are usually energetically more favorable at room temperature because of the entropy contribution. This phenomenon is not guaranteed in van der Waals 2D materials due to the reduced dimensionality (reduced entropy)...
October 17, 2016: Small
Feifan Yu, Qianwen Liu, Xin Gan, Mingxiang Hu, Tianyi Zhang, Cheng Li, Feiyu Kang, Mauricio Terrones, Ruitao Lv
Ultrasensitive pressure sensors are constructed with few-layer MoS2 films. As-designed Fabry-Perot (F-P) sensors exhibit nearly synchronous pressure-deflection responses with a very high sensitivity (89.3 nm Pa(-1) ), which is three orders of magnitude higher than those of conventional diaphragm materials (e.g., silica, silver films). This kind of F-P sensor may open up new avenues for 2D materials in biomedical and environmental applications.
October 17, 2016: Advanced Materials
Menghao Wu, Shuai Dong, Kailun Yao, Jun-Ming Liu, Xiao Cheng Zeng
Realization of ferroelectric semiconductors by conjoining ferroelectricity with semiconductors remain a challenging task because most present-day ferroelectric materials are unsuitable for such a combination due to their wide bandgaps. Herein we show first-principles evidence towards the realization of a new class of 2D ferroelectric semiconductors through covalent functionalization of many prevailing 2D materials. Members in this new class of 2D ferroelectric semiconductors include covalently functionalized germanene, and stanene (Nat...
October 14, 2016: Nano Letters
Jianping Shi, Rui Tong, Xiebo Zhou, Yue Gong, Zhepeng Zhang, Qingqing Ji, Yu Zhang, Qiyi Fang, Lin Gu, Xina Wang, Zhongfan Liu, Yanfeng Zhang
A growth-temperature-mediated two-step chemical vapor deposition strategy is designed to synthesize MoS2 /WS2 and WS2 /MoS2 stacks on Au foils. Predominantly A-A stacked MoS2 /WS2 and A-B stacked WS2 /MoS2 are selectively achieved and confirmed. Relative enhancements or reductions in photocatalytic activities of MoS2 /WS2 or WS2 /MoS2 are observed under illumination, because the type-II band alignment enables directional electron flow from electrode to active site.
October 14, 2016: Advanced Materials
Dingbin Xiao, Jinying Zhang, Xin Li, Dan Zhao, Hongyang Huang, Jialiang Huang, Daxian Cao, Zhihui Li, Chunming Niu
The morphology and hybridization of nanostructures are crucial to achieve properties for various applications. An in situ grown 3D MoS2 nano-mask has been adopted to control the morphology and hybridization of molybdenum compounds. The in situ generated MoS2 mask on MoO3 nanobelt surfaces allowed us to fabricate a 3D c-MoO2@MoS2 hybrid nanostructure, in which c-MoO2 is a carved MoO2 nanobelt with well distributed hole-pattern. The nano-masks have been controlled by adjusting the alignments of MoS2. The exposed MoO2 surfaces of c-MoO2@MoS2 were further sulphurated to give cw-MoO2@MoS2, in which all surfaces of MoO2 are wrapped by a few layers of MoS2...
October 12, 2016: ACS Nano
Habib Rostami, Reza Asgari, Francisco Guinea
We explore the electronic structure, orbital character and topological aspect of a monolayer MoS2 nanoribbon using tight-binding (TB) and low-energy ([Formula: see text]) models. We obtain a mid-gap edge mode in the zigzag ribbon of monolayer MoS2, which can be traced back to the topological properties of the bulk band structure. Monolayer MoS2 can be considered as a valley Hall insulator. The boundary conditions at armchair edges mix the valleys on the edges, and a gap is induced in the edge modes. The spin-orbit coupling in the valence band reduces the hybridization of the bulk states...
October 12, 2016: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Yanming Ju, Yuan Meng, Yingjin Wei, Xiaofei Bian, Qiang Pang, Yu Gao, Fei Du, Bingbing Liu, Gang Chen
The demand for large-scale and high-safe energy storage is increasing rapidly due to the strong push for smartphone and electric vehicles. The Li+/Mg2+ hybrid-ion batteries (LMIBs) combing a dendrite-free deposition of Mg anode and Li+ intercalation cathode attract considerable attentions. Here we report a LMIB using the hydrothermal-prepared MoS2 nano flowers as the cathode material. The battery showed remarkable electrochemical properties with a large discharge capacity (243 mAh g-1 at the 0.1 C rate), excellent rate capability (108 mAh g-1 at the 5 C rate) and long cycle life (87...
October 11, 2016: Chemistry: a European Journal
Tom T A Lummen, Raymond J Lamb, Gabriele Berruto, Thomas LaGrange, Luca Dal Negro, F Javier García de Abajo, Damien McGrouther, B Barwick, F Carbone
Capturing and controlling plasmons at buried interfaces with nanometre and femtosecond resolution has yet to be achieved and is critical for next generation plasmonic devices. Here we use light to excite plasmonic interference patterns at a buried metal-dielectric interface in a nanostructured thin film. Plasmons are launched from a photoexcited array of nanocavities and their propagation is followed via photon-induced near-field electron microscopy (PINEM). The resulting movie directly captures the plasmon dynamics, allowing quantification of their group velocity at ∼0...
October 11, 2016: Nature Communications
Emily P Nguyen, Benjamin J Carey, Christopher J Harrison, Paul Atkin, Kyle J Berean, Enrico Della Gaspera, Jian Zhen Ou, Richard B Kaner, Kourosh Kalantar-Zadeh, Torben Daeneke
Two-dimensional (2D) transition metal chalcogenides such as 2D MoS2 are considered prime candidate materials for the design of next generation optoelectronics. Functionalisation of these materials is considered to be a key step in tailoring their properties towards specific applications and unlocking their full potential. Here we present a van der Waals functionalisation strategy for creating MoS2 nanosheets decorated with free base phthalocyanine chromophores. The semiconducting sheets are found to intimately interact with these optoelectronically active chromophores, resulting in an electronic heterostructure that exhibits enhanced optoelectronic properties and exploitable charge transfer...
September 15, 2016: Nanoscale
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