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Gustavo A Saenz, Goran Karapetrov, James Curtis, Anupama B Kaul
The design, fabrication, and characterization of ultra-high responsivity photodetectors based on mesoscopic multilayer MoS2 is presented, which is a less explored system compared to direct band gap monolayer MoS2 that has received increasing attention in recent years. The device architecture is comprised of a metal-semiconductor-metal (MSM) photodetector, where Mo was used as the contact metal to suspended MoS2 membranes. The photoresponsivity [Formula: see text] was measured to be ~1.4 × 104 A/W, which is > 104 times higher compared to prior reports, while the detectivity D* was computed to be ~2...
January 19, 2018: Scientific Reports
Dawei Li, Zhiyong Xiao, Sai Mu, Fei Wang, Ying Liu, Jingfeng Song, Xi Huang, Lijia Jiang, Jun Xiao, Lei Liu, Stephen Ducharme, Bai Cui, Xia Hong, Lan Jiang, Jean-Francois Silvain, Yongfeng Lu
Single-crystal transition metal dichalcogenides (TMDs) and TMD-based hetero-junctions have recently attracted significant research and industrial interest owing to their intriguing optical and electrical properties. However, the lack of a simple, low-cost, environmentally friendly, synthetic method and a poor understanding of the growth mechanism post a huge challenge to implementing TMDs in practical applications. In this work, we developed a novel approach for direct formation of high-quality, monolayer and few-layer MoS2 single crystal domains via a single-step rapid thermal processing of a sandwiched reactor with sulfur and molybdenum (Mo) film in a confined reaction space...
January 19, 2018: Nano Letters
Sunny Gupta, Sharmila N Shirodkar, Daniel Kaplan, Venkataraman Swaminathan, Boris I Yakobson
Optical spectroscopy (OS) techniques are often coupled with first-principles density functional theoretical (DFT) calculations for determining the precise influence of defects on the electronic and structural properties of two dimensional (2D) TMDs. Such calculations are carried out presuming there is little or no effect of vibrational transitions on the observed electronic spectrum. However, if the effect of change in vibrational energy [Franck Condon (FC) shift] associated with such a transition is large, it could possibly lead to a different origin for the observed peak...
January 19, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Zenghui Wu, Guoan Tai, Xufeng Wang, Tingsong Hu, Rui Wang, Wanlin Guo
Compared with MoS2 and WS2, the selenide analogues have narrower band gaps and higher electron mobilities, which make them more applicable to real electrical devices. Besides, few-layered metal selenides have higher electrical conductivity, carrier mobility and light absorption than the corresponding monolayers. However, the large-scale and high-quality growth of few-layered metal selenides remains a significant challenge. Here, we develop a facile method to grow large-area and highly-crystalline few-layered MoSe2 by directly selenizing the Mo foil surfaces at 550 oC within 60 min under ambient pressure...
January 18, 2018: Nanotechnology
Hong-Hui Wu, Qiangqiang Meng, He Huang, C T Liu, Xun-Li Wang
The application of the reported armchair transition-metal dichalcogenide (MoS2, MoTe2, MoSTe and WS2, etc.) nanotube is hindered for the optoelectronic devices due to the indirect band gap. By using first-principles calculations, the electronic structures of MoS2-xSex single-wall armchair nanotubes with respect to different diameters are investigated. The MoS2 armchair nanotube exhibits an indirect band gap as a function of nanotube diameters from 10 Å to 50 Å, whereas MoSSe and MoSe2 exhibit a surprising diameter-induced indirect-direct band gap crossover at the diameters of 25 Å and 33 Å, respectively...
January 17, 2018: Physical Chemistry Chemical Physics: PCCP
Yee-Fun Lim, Kumar Priyadarshi, Fabio Bussolotti, Pranjal Kumar Gogoi, Xiaoyang Cui, Ming Yang, Jisheng Pan, Shi Wun Tong, Shijie Wang, Stephen J Pennycook, Kuan Eng Johnson Goh, Andrew T S Wee, Swee Liang Wong, Dongzhi Chi
Single-layer molybdenum disulfide (MoS2) has attracted significant attention due to its unique electronic and physical properties with much effort invested towards obtaining large area high quality monolayer MoS2 films. In this work, we demonstrate a reactive barrier-based approach to achieve growth of highly homogeneous single layer MoS2 on sapphire through the use of a nickel oxide foam barrier during chemical vapor deposition. Due to the reactivity of the NiO barrier with MoO3, the concentration of precursors reaching the substrate and thus nucleation density is effectively reduced, allowing grain sizes of up to 170 µm and continuous monolayers on the centimeter length scale being obtained...
January 16, 2018: ACS Nano
Finn Purcell-Milton, Robert McKenna, Lorcan Brennan, Conor P Cullen, Lilian Guillemeney, Nikita V Tepliakov, Anvar S Baimuratov, Ivan D Rukhlenko, Tatiana S Perova, Georg S Duesberg, Alexander V Baranov, Anatoly V Fedorov, Yurii K Gun'ko
Two-dimensional (2D) nanomaterials have been intensively investigated due to their interesting properties and range of potential applications. Although most research has focused on graphene, atomic layered transition metal dichalcogenides (TMDs) and particularly MoS2 have gathered much deserved attention recently. Here we report the induction of chirality into 2D chiral nanomaterials by carrying out liquid exfoliation of MoS2 in the presence of chiral ligands (cysteine and penicillamine) in water. This processing resulted in exfoliated chiral 2D MoS2 nanosheets showing strong circular dichroism (CD) signals, which were far past the onset of the original chiral ligand signals...
January 16, 2018: ACS Nano
Amreen Bano, N K Gaur
A variety of theoretical and experimental works have reported several potential applications of MoS2 monolayer based heterostructures (HSs) such as light emitting diodes, photodetectors and field effect transistors etc. In the present work, we have theoretically performed as a model case study, MoS2 monolayer deposited over insulating SrTiO3 (001) to study the band alignment at TiO2 termination. The interfacial characteristics are found to be highly dependent on the interface termination. With an insulating oxide material, a significant band gap (0...
January 15, 2018: Scientific Reports
Chendong Zhang, Ming-Yang Li, Jerry Tersoff, Yimo Han, Yushan Su, Lain-Jong Li, David A Muller, Chih-Kang Shih
Monolayer transition metal dichalcogenide heterojunctions, including vertical and lateral p-n junctions, have attracted considerable attention due to their potential applications in electronics and optoelectronics. Lattice-misfit strain in atomically abrupt lateral heterojunctions, such as WSe2-MoS2, offers a new band-engineering strategy for tailoring their electronic properties. However, this approach requires an understanding of the strain distribution and its effect on band alignment. Here, we study a WSe2-MoS2 lateral heterojunction using scanning tunnelling microscopy and image its moiré pattern to map the full two-dimensional strain tensor with high spatial resolution...
January 15, 2018: Nature Nanotechnology
Joonki Suh, Teck Leong Tan, Weijie Zhao, Joonsuk Park, Der-Yuh Lin, Tae-Eon Park, Jonghwan Kim, Chenhao Jin, Nihit Saigal, Sandip Ghosh, Zicong Marvin Wong, Yabin Chen, Feng Wang, Wladyslaw Walukiewicz, Goki Eda, Junqiao Wu
Doping of traditional semiconductors has enabled technological applications in modern electronics by tailoring their chemical, optical and electronic properties. However, substitutional doping in two-dimensional semiconductors is at a comparatively early stage, and the resultant effects are less explored. In this work, we report unusual effects of degenerate doping with Nb on structural, electronic and optical characteristics of MoS2 crystals. The doping readily induces a structural transformation from naturally occurring 2H stacking to 3R stacking...
January 15, 2018: Nature Communications
Li Li, Yichuan Guo, Yuping Sun, Long Yang, Liang Qin, Shouliang Guan, Jinfen Wang, Xiaohui Qiu, Hongbian Li, Yuanyuan Shang, Ying Fang
The capability to directly build atomically thin transition metal dichalcogenide (TMD) devices by chemical synthesis offers important opportunities to achieve large-scale electronics and optoelectronics with seamless interfaces. Here, a general approach for the chemical synthesis of a variety of TMD (e.g., MoS2 , WS2 , and MoSe2 ) device arrays over large areas is reported. During chemical vapor deposition, semiconducting TMD channels and metallic TMD/carbon nanotube (CNT) hybrid electrodes are simultaneously formed on CNT-patterned substrate, and then coalesce into seamless devices...
January 15, 2018: Advanced Materials
Anthony Yoshimura, Michael Lamparski, Neerav Kharche, Vincent Meunier
Electron beam irradiation by transmission electron microscopy (TEM) is a common and effective method for post-synthesis defect engineering in two-dimensional transition metal dichalcogenides (TMDs). Combining density functional theory (DFT) with relativistic scattering theory, we simulate the generation of such defects in monolayer group-VI TMDs, MoS2, WS2, MoSe2, and WSe2, focusing on two fundamental TEM-induced atomic displacement processes: chalcogen sputtering and chalcogen vacancy migration. Our calculations show that the activation energies of chalcogen sputtering depend primarily on the chalcogen species, and are smaller in selenides than in sulfides...
January 15, 2018: Nanoscale
Chaoliang Tan, Zhimin Luo, Apoorva Chaturvedi, Yongqing Cai, Yonghua Du, Yue Gong, Ying Huang, Zhuangchai Lai, Xiao Zhang, Lirong Zheng, Xiaoying Qi, Min Hao Goh, Jie Wang, Shikui Han, Xue-Jun Wu, Lin Gu, Christian Kloc, Hua Zhang
Nanostructured transition metal dichalcogenides (TMDs) are proven to be efficient and robust earth-abundant electrocatalysts to potentially replace precious platinum-based catalysts for the hydrogen evolution reaction (HER). However, the catalytic efficiency of reported TMD catalysts is still limited by their low-density active sites, low conductivity, and/or uncleaned surface. Herein, a general and facile method is reported for high-yield, large-scale production of water-dispersed, ultrasmall-sized, high-percentage 1T-phase, single-layer TMD nanodots with high-density active edge sites and clean surface, including MoS2 , WS2 , MoSe2 , Mo0...
January 15, 2018: Advanced Materials
Ti-Long Yang, Shao-Fei Ni, Peng Qin, Li Dang
Density functional theory (DFT) calculations show that H2 evolution is attributed to active sulfur hydrides derived from MoS2 complexes via two- or three-electron reduction from the synthesized [(PY5Me2)MoS2]2+. Water acts as a bridge for H2 evolution from the intermolecular H+/H- coupling between sulfur hydride complexes and hydrated protons.
January 15, 2018: Chemical Communications: Chem Comm
Samira Mansouri Majd, Abdollah Salimi, Foad Ghasemi
MicroRNAs (miRNAs), critical biomarkers of acute and chronic diseases, play key regulatory roles in many biological processes. As a result, robust assay platforms to enable an accurate and efficient detection of low-level miRNAs in complex biological samples are of great significance. In this work, a label-free and direct hybridization assay using molybdenum disulfide (MoS2) field-effect transistor (FET) biosensor has been developed for ultrasensitive detection of miRNA-155 as a breast cancer biomarker in human serum and cell-line samples...
January 6, 2018: Biosensors & Bioelectronics
Huaizhi Liu, Liao Xu, Weixu Liu, Bo Zhou, Yinyan Zhu, Lihua Zhu, Xiaoqing Jiang
Here, we report a facile salt-assisted direct liquid-phase exfoliation method for mass production of MoS2 nanosheets. We choose organic solvent isopropanol (IPA) as exfoliation media and potassium ferrocyanide, potassium sodium tartrate, or sodium tartrate as salt, the assistant. The selected salts show universal and efficient assistant effect for the exfoliation of MoS2 in IPA. Especially, potassium ferrocyanide (K4Fe(CN)6) can enhance the exfoliation efficiency up to 73 times and a dispersion of MoS2 nanosheets with concentration as high as 0...
January 6, 2018: Journal of Colloid and Interface Science
Jun Zhang, Hao Ouyang, Xin Zheng, Jie You, Runze Chen, Tong Zhou, Yizhen Sui, Yu Liu, Xiang'ai Cheng, Tian Jiang
The newly raised two-dimensional material MoS2 is regarded as an ideal candidate for saturated absorbers. Here, the open-aperture Z-scan method is used to study the saturation absorption (SA) response of monolayer and multilayer MoS2, considering laser irradiation with different pulse widths. Specifically, in cases of 10 ns and 10 ps laser pulses, the accumulative nonlinearity [e.g., free carrier absorption (FCA)] coupled with SA is found in both monolayer and multilayer MoS2. However, under a 65 fs pulse laser, the instantaneous nonlinearity [e...
January 15, 2018: Optics Letters
Kuang-I Lin, Yen-Hung Ho, Shu-Bai Liu, Jian-Jhih Ciou, Bo-Ting Huang, Christopher Chen, Han-Ching Chang, Chien-Liang Tu, Chang-Hsiao Chen
Edge morphology and lattice orientation of single-crystal molybdenum disulfide (MoS2) monolayers, a transition metal dichalcogenide (TMD), possessing a triangular shape with different edges grown by chemical vapor deposition are characterized by atomic force microscopy and transmission electron microscopy. Multiphoton laser scanning microscopy is utilized to study one-dimensional atomic edges of MoS2 monolayers with localized mid-gap electronic states, which result in greatly enhanced optical second-harmonic generation (SHG)...
January 12, 2018: Nano Letters
Liang Zhang, Dan Sun, Jun Kang, Jun Feng, Hans A Bechtel, Lin-Wang Wang, Elton J Cairns, Jinghua Guo
As a typical transition metal dichalcogenide, MoS2 offers numerous advantages for nanoelectronics and electrochemical energy storage due to its unique layered structure and tunable electronic properties. When used as the anode in lithium-ion cells, MoS2 undergoes intercalation and conversion reactions in sequence upon lithiation, and the reversibility of the conversion reaction is an important but still controversial topic. Here, we clarify unambiguously that the conversion reaction of MoS2 is not reversible and the formed Li2S is converted to sulfur in the first charge process...
January 12, 2018: Nano Letters
Liu Wang, Zhicheng Huang, Rui Wang, Yibo Liu, Cheng Qian, Jian Wu, Juewen Liu
Monitoring the progress of polymerase chain reactions (PCR) is of critical importance in bioanalytical chemistry and molecular biology. While real-time PCR thermocyclers are ideal for this purpose, its high cost has limited applications in resource-poor areas. Direct visual detection would be a more attractive alternative. To monitor PCR amplification, DNA staining dyes such as SYBR Green I (SG) are often used. Although these dyes give higher fluorescence when binding to double-stranded (ds) DNA products, they also yield strong background fluorescence in the presence of a high concentration of single-stranded (ss) DNA primers...
January 12, 2018: ACS Applied Materials & Interfaces
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