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Meng-Lin Tsai, Ming-Yang Li, José Ramón Durán Retamal, Kai-Tak Lam, Yung-Chang Lin, Kazu Suenaga, Lih-Juann Chen, Gengchiau Liang, Lain-Jong Li, Jr-Hau He
The recent development of 2D monolayer lateral semiconductor has created new paradigm to develop p-n heterojunctions. Albeit, the growth methods of these heterostructures typically result in alloy structures at the interface, limiting the development for high-efficiency photovoltaic (PV) devices. Here, the PV properties of sequentially grown alloy-free 2D monolayer WSe2 -MoS2 lateral p-n heterojunction are explores. The PV devices show an extraordinary power conversion efficiency of 2.56% under AM 1.5G illumination...
June 26, 2017: Advanced Materials
Peng Zhao, Angelica Azcatl, Yuri Y Gomeniuk, Pavel Bolshakov, Michael Schmidt, Stephen J McDonnell, Christopher L Hinkle, Paul K Hurley, Robert M Wallace, Chadwin Young
The electronic properties of the HfO2/MoS2 interface were investigated using multi-frequency capacitance-voltage (C-V) and current-voltage characterization of top gated MoS2 metal oxide semiconductor field effect transistors. The analysis was performed on few layer (5 - 10) MoS2 MOSFETs fabricated using photolithographic patterning with 13 nm and 8 nm HfO2 gate oxide layers formed by atomic layer deposition after in-situ UV-O3 surface functionalization. The impedance response of the HfO2/MoS2 gate stack indicates the existence of specific defects at the interface, which exhibited either a frequency dependent distortion similar to conventional Si MOSFETs with unpassivated silicon dangling bonds, or a frequency dispersion over the entire voltage range corresponding to depletion of the HfO2/MoS2 surface, consistent with interface traps distributed over a range of energy levels...
June 26, 2017: ACS Applied Materials & Interfaces
Kai-Chun Lin, Badrinath Jagannath, Sriram Muthukumar, Shalini Prasad
An ultrasensitive aptasensor for the label free non-faradaic detection of thrombin has been demonstrated on molybdenum disulphide (MoS2) nanosheets. These nanosheets were physiochemically immobilized onto a silicon micro-electrode platform. Thrombin detection was achieved through the charge modulation of the electrical double layer due to the specific and dose dependent binding of thrombin to the surface of thiol terminated ssDNA aptamer functionalized MoS2 nanosheets. Electrical double layer charge modulation associated with thrombin binding was characterized using electrochemical impedance spectroscopy...
June 26, 2017: Analyst
Peifeng Li, Chenchen Jiang, Shang Xu, Yu Zhuang, Libo Gao, Alice Hu, Hongtao Wang, Yang Lu
Layered molybdenum disulfide (MoS2) exhibits rich electronic and optical properties and possesses vastly differing characteristic dimensions. A multi-layer MoS2 membrane represents the critical hierarchical structure which bridges the length-scale of monolayer and bulk material architectures. In this study, the in-plane mechanical properties of MoS2 membranes were investigated by in situ SEM tensile testing. Under the uniaxial tensile loading, brittle fracture caused failure in a highly localized region of the MoS2 membranes and their mechanical properties showed a thickness effect: the strengths of the relatively thicker MoS2 membranes (thickness around hundreds of nanometers) distribute from ∼100 to ∼250 MPa, while the corresponding values of the MoS2 nanosheets (thickness around tens of nanometers) increase significantly to more than 1 GPa...
June 23, 2017: Nanoscale
Jae-Hyuk Ahn, William M Parkin, Carl H Naylor, A T Charlie Johnson, Marija Drndić
Monolayer materials are sensitive to their environment because all of the atoms are at their surface. We investigate how exposure to the environment affects the electrical properties of CVD-grown monolayer MoS2 by monitoring electrical parameters of MoS2 field-effect transistors as their environment is changed from atmosphere to high vacuum. The mobility increases and contact resistance decreases simultaneously as either the pressure is reduced or the sample is annealed in vacuum. We see a previously unobserved, non-monotonic change in threshold voltage with decreasing pressure...
June 22, 2017: Scientific Reports
Wei Tao, Xiaoyuan Ji, Xiaoding Xu, Mohammad Ariful Islam, Zhongjun Li, Si Chen, Phei Er Saw, Han Zhang, Zameer Bharwani, Zilei Guo, Jinjun Shi, Omid Farokhzad
Photothermal therapy (PTT) has shown significant potential for cancer therapy. However, developing nanomaterials (NMs)-based photothermal agents (PTAs) with satisfactory photothermal conversion efficacy (PTCE) and biocompatibility remains a key challenge. Herein, a new generation of PTAs based on two-dimensional (2D) antimonene quantum dots (AMQDs) was developed by a novel liquid exfoliation method. Surface modification of AMQDs with polyethylene glycol (PEG) significantly enhanced both biocompatibility and stability in physiological medium...
June 22, 2017: Angewandte Chemie
Guijian Guan, Jing Xia, Shuhua Liu, Yuan Cheng, Shiqiang Bai, Si Yin Tee, Yong-Wei Zhang, Ming-Yong Han
Here, direct and effective electrostatic-driven exfoliation of tungsten trioxide (WO3 ) powder into atomically thin WO3 nanosheets is demonstrated for the first time. Experimental evidence together with theoretical simulations clearly reveal that the strong binding of bovine serum albumin (BSA) on the surface of WO3 via the protonation of NH2 groups in acidic conditions leads to the effective exfoliation of WO3 nanosheets under sonication. The exfoliated WO3 nanosheets have a greatly improved dispersity and stability due to surface-protective function of BSA, and exhibit a better performance and unique advantages in applications such as visible-light-driven photocatalysis, high-capacity adsorption, and fast electrochromics...
June 22, 2017: Advanced Materials
Yong-Chao Rao, Song Yu, Xiang-Mei Duan
Hybrid structures have attracted a great deal of attention because of their excellent properties, which can open up a way we could not foresee in materials science and device physics. Here, we investigate the electrical and optical behaviors of SiC(GeC)/MoS2 heterostructures, using first principles calculations based on density functional theory. Non-covalent bonding exists between the junctions due to the weak orbital coupling. Both junctions have optically active band gaps, smaller than that of the SiC or GeC and MoS2 layers, which result in enhanced optical adsorption under visible-light irradiation...
June 22, 2017: Physical Chemistry Chemical Physics: PCCP
Wenguang Tu, Yichang Li, Libang Kuai, Yong Zhou, Qinfeng Xu, Haijin Li, Xiaoyong Wang, Min Xiao, Zhigang Zou
Two-dimensional MoS2 nanosheets were in situ grown on TiO2 nanosheets to form two-dimensional (2D) hybrid nanojunctions, with which MoS2 nanosheets compactly contact with TiO2 to increase the interfacial area. MoS2 was identified as a promising cost-effective substitute for noble metal cocatalysts such as Pt, Au, and Ag, and shows superior activity and selectivity for reducing CO2 to CH3OH in aqueous solution to these metal cocatalysts under UV-vis light irradiation. The photo-luminescence (PL) spectra and transient time-resolved PL decay measurements reveal that the fast electron transfer from TiO2 to MoS2 can minimize charge recombination losses to improve the conversion efficiency of photoreduction...
June 22, 2017: Nanoscale
Xiankun Zhang, Qingliang Liao, Shuo Liu, Zhuo Kang, Zheng Zhang, Junli Du, Feng Li, Shuhao Zhang, Jiankun Xiao, Baishan Liu, Yang Ou, Xiaozhi Liu, Lin Gu, Yue Zhang
We establish a powerful poly(4-styrenesulfonate) (PSS)-treated strategy for sulfur vacancy healing in monolayer MoS2 to precisely and steadily tune its electronic state. The self-healing mechanism, in which the sulfur vacancies are healed spontaneously by the sulfur adatom clusters on the MoS2 surface through a PSS-induced hydrogenation process, is proposed and demonstrated systematically. The electron concentration of the self-healed MoS2 dramatically decreased by 643 times, leading to a work function enhancement of ∼150 meV...
June 22, 2017: Nature Communications
Lei Fu, Feng Wang, Bin Wu, Nian Wu, Wei Huang, Hanlin Wang, Chuanhong Jin, Lin Zhuang, Jun He, Lei Fu, Yunqi Liu
As a member of the group IVB transition metal dichalcogenides (TMDs) family, hafnium disulfide (HfS2 ) is recently predicted to exhibit higher carrier mobility and higher tunneling current density than group VIB (Mo and W) TMDs. However, the synthesis of high-quality HfS2 crystals, sparsely reported, has greatly hindered the development of this new field. Here, a facile strategy for controlled synthesis of high-quality atomic layered HfS2 crystals by van der Waals epitaxy is reported. Density functional theory calculations are applied to elucidate the systematic epitaxial growth process of the S-edge and Hf-edge...
June 22, 2017: Advanced Materials
Mao-Lin Shi, Lin Chen, Tian-Bao Zhang, Jing Xu, Hao Zhu, Qing-Qing Sun, David Wei Zhang
The lack of stable and efficient techniques to synthesize high-quality large-area thin films is one of the major bottlenecks for the real-world application of the 2D transition metal dichalcogenides. In this work, the growth of molybdenum disulfide (MoS2 ) on sapphire substrates by sulfurizing the MoO3 film deposited by atomic layer deposition (ALD) is reported. The advantages of the ALD method can be well inherited, and the synthesized MoS2 films exhibit excellent layer controllability, wafer-scale uniformity, and homogeneity...
June 22, 2017: Small
Satoshi Yasuda, Ryosuke Takahashi, Ryo Osaka, Ryota Kumagai, Yasumitsu Miyata, Susumu Okada, Yuhei Hayamizu, Kei Murakoshi
Making contact of transition metal dichalcogenides (TMDCs) with a metal surface is essential for fabricating and designing electronic devices and catalytic systems. It also generates strain in the TMDCs that plays significant role in both electronic and phonon structures. Therefore, detailed understanding of mechanism of the strain generation is important to fully comprehend the modulation effect for the electronic and phonon properties. Here, MoS2 and MoSe2 monolayers are grown on Au surface by chemical vapor deposition and it is demonstrated that the contact with a crystalline Au(111) surface gives rise to only out-of-plane strain in both MoS2 and MoSe2 layers, whereas no strain generation is observed on polycrystalline Au or SiO2 /Si surfaces...
June 22, 2017: Small
Xin Lu, M I B Utama, Xingzhi Wang, Weigao Xu, Weijie Zhao, Man Hon Samuel Owen, Qihua Xiong
The gate-tunable phonon properties in bilayer MoS2 are shown to be dependent on excitation energy. Raman intensity, Raman shift, and linewidth are affected by resonant excitation, while a nonresonant laser does not influence the intensity significantly. The gate-dependent Raman shift of A1g mode (either blue-, red-, or no-shift) is a result of the combined effect of antibonding electron and resonant-related decoupling effect. Although the decoupling effect cannot be directly measured due to the resonant background, it can be indirectly and qualitatively probed by observing A1g mode...
June 22, 2017: Small
D W Li, Q M Zou, X Huang, H Rabiee Golgir, K Keramatnejad, J F Song, Z Y Xiao, L S Fan, X Hong, L Jiang, J F Silvain, S Sun, Y F Lu
It is known that defects strongly influence the properties of two-dimensional (2D) materials. The controlled creation and removal of defects can be utilized to tailor the optical and electronic responses of these 2D materials for optoelectronic and nanoelectronic applications. In this study, we developed an efficient approach to reversibly control the defect states in mechanically exfoliated graphene and molybdenum disulfide (MoS2) monolayers. The defects were created by aluminium oxide (Al2O3) plasmas and removed by moderate thermal annealing at up to 300 °C...
June 22, 2017: Nanoscale
Bong Ho Kim, Hyun Ho Gu, Young Joon Yoon
We synthesised a crystalline MoS2 film from as-sputtered amorphous film by applying an electron beam irradiation (EBI) process. A collimated electron beam (60 mm dia.) with an energy of 1 kV was irradiated for only 1 min to achieve crystallisation without an additional heating process. After the EBI process, we observed a two-dimensional layered structure of MoS2 about 4 nm thick and with a hexagonal atomic arrangement on the surface. A stoichiometric MoS2 film was confirmed to grow well on SiO2/Si substrates and include partial oxidation of Mo...
June 20, 2017: Scientific Reports
Deyi Fu, Xiaoxu Zhao, Yu-Yang Zhang, Linjun Li, Hai Xu, A-Rang Jang, Seong In Yoon, Peng Song, Sock Mui Poh, Tianhua Ren, Zijing Ding, Wei Fu, Tae Joo Shin, Hyeon Suk Shin, Sokrates T Pantelides, Wu Zhou, Kian Ping Loh
Atomically thin molybdenum disulfide (MoS2), a direct-band-gap semiconductor, is promising for applications in electronics and optoelectronics but the scalable synthesis of highly-crystalline film remains challenging. Here we report the successful epitaxial growth of a continuous, uniform, highly-crystalline monolayer MoS2 film on hexagonal boron nitride (h-BN) by molecular beam epitaxy. Atomic force microscopy and electron microscopy studies reveal that MoS2 grown on h-BN primarily consists of two types of nucleation grains (0o aligned and 60o anti-aligned domains)...
June 21, 2017: Journal of the American Chemical Society
Xiu Liang, Yi-Shuo Wang, Ting-Ting You, Xiao-Juan Zhang, Nan Yang, Guang-Sheng Wang, Peng-Gang Yin
Interfacial self-assembly of ordered nanostructures at oil-water interfaces towards the fabrication of nanofilms has attracted the interest of plenty of scientists, since its discovery in 2004. Herein, further developments have been achieved, and we report a new strategy for the synthesis of a three-dimensional (3D) hierarchical nanostructure, through an interfacial synthesis driven microemulsion process. Thus, the synthesis route has been simplified, with the rigorous experimental conditions of traditional compositing technology...
June 20, 2017: Nanoscale
Cuicui Ling, Tianchao Guo, Wenbo Lu, Ya Xiong, Lei Zhu, Qingzhong Xue
The SnO2/Si heterojunction possesses a large band offset and it is easy to control the transportation of carriers in the SnO2/Si heterojunction to realize high-response broadband detection. Therefore, we investigated the potential of the SnO2 nanoparticle thin film/SiO2/p-Si heterojunction for photodetectors. It is demonstrated that this heterojunction shows a stable, repeatable and broadband photoresponse from 365 nm to 980 nm. Meanwhile, the responsivity of the device approaches a high value in the range of 0...
June 20, 2017: Nanoscale
Adam L Friedman, Aubrey T Hanbicki, F Keith Perkins, Glenn G Jernigan, James C Culbertson, Paul M Campbell
Electron-donors can impart charge to the surface of transition metal dichalcogenide (TMD) films while interacting with the film via a weak physisorption bond, making them ideal for vapor and gas sensors. We expose monolayer MoS2 and MoSe2 films to strong electron-donor chemical vapor analytes. After analyzing the resultant behavior and taking into consideration doping effects, we conclude that exposure to strong electron-donors could be a method of inducing the semiconductor-metal 2H-1T TMD phase transition...
June 19, 2017: Scientific Reports
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