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1.
Probing Anisotropic Thermal Conductivity of Transition Metal Dichalcogenides MX2 (M = Mo,W and X = S,Se) using Time‐Domain Thermoreflectance
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Puqing Jiang Xin Qian Xiaokun Gu Ronggui Yang 《Advanced materials (Deerfield Beach, Fla.)》2017,29(36)
Transition metal dichalcogenides (TMDs) are a group of layered 2D semiconductors that have shown many intriguing electrical and optical properties. However, the thermal transport properties in TMDs are not well understood due to the challenges in characterizing anisotropic thermal conductivity. Here, a variable‐spot‐size time‐domain thermoreflectance approach is developed to simultaneously measure both the in‐plane and the through‐plane thermal conductivity of four kinds of layered TMDs (MoS2, WS2, MoSe2, and WSe2) over a wide temperature range, 80–300 K. Interestingly, it is found that both the through‐plane thermal conductivity and the Al/TMD interface conductance depend on the modulation frequency of the pump beam for all these four compounds. The frequency‐dependent thermal properties are attributed to the nonequilibrium thermal resistance between the different groups of phonons in the substrate. A two‐channel thermal model is used to analyze the nonequilibrium phonon transport and to derive the intrinsic thermal conductivity at the thermal equilibrium limit. The measurements of the thermal conductivities of bulk TMDs serve as an important benchmark for understanding the thermal conductivity of single‐ and few‐layer TMDs. 相似文献
2.
Insight into In Situ Amphiphilic Functionalization of Few‐Layered Transition Metal Dichalcogenide Nanosheets
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Jianfeng Shen Jingjie Wu Man Wang Yuancai Ge Pei Dong Robert Baines Gustavo Brunetto Leonardo D. Machado Pulickel M. Ajayan Mingxin Ye 《Advanced materials (Deerfield Beach, Fla.)》2016,28(38):8469-8476
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Yin‐Ting Yeh Zhong Lin Kazunori Fujisawa Yu Lei Yijing Zhou Christopher Rotella Ana Laura Elías Si‐Yang Zheng Yingwei Mao Zhiwen Liu Huaguang Lu Mauricio Terrones 《Advanced materials (Deerfield Beach, Fla.)》2018,30(8)
2D materials cover a wide spectrum of electronic properties. Their applications are extended from electronic, optical, and chemical to biological. In terms of biomedical uses of 2D materials, the interactions between living cells and 2D materials are of paramount importance. However, biointerfacial studies are still in their infancy. This work studies how living organisms interact with transition metal dichalcogenide monolayers. For the first time, cellular digestion of tungsten disulfide (WS2) monolayers is observed. After digestion, cells intake WS2 and become fluorescent. In addition, these light‐emitting cells are not only viable, but also able to pass fluorescent signals to their progeny cells after cell division. By combining synthesis of 2D materials and a cell culturing technique, a procedure for monitoring the interactions between WS2 monolayers and cells is developed. These observations open up new avenues for developing novel cellular labeling and imaging approaches, thus triggering further studies on interactions between 2D materials and living organisms. 相似文献
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Gwang‐Hyeon Nam Qiyuan He Xingzhi Wang Yifu Yu Junze Chen Kang Zhang Zhenzhong Yang Dianyi Hu Zhuangchai Lai Bing Li Qihua Xiong Qing Zhang Lin Gu Hua Zhang 《Advanced materials (Deerfield Beach, Fla.)》2019,31(21)
Crystal phases play a key role in determining the physicochemical properties of a material. To date, many phases of transition metal dichalcogenides have been discovered, such as octahedral (1T), distorted octahedral (1T′), and trigonal prismatic (2H) phases. Among these, the 1T′ phase offers unique properties and advantages in various applications. Moreover, the 1T′ phase consists of unique zigzag chains of the transition metals, giving rise to interesting in‐plane anisotropic properties. Herein, the in‐plane optical and electrical anisotropies of metastable 1T′‐MoS2 layers are investigated by the angle‐resolved Raman spectroscopy and electrical measurements, respectively. The deconvolution of J1 and J2 peaks in the angle‐resolved Raman spectra is a key characteristic of high‐quality 1T′‐MoS2 crystal. Moreover, it is found that its electrocatalytic performance may be affected by the crystal orientation of anisotropic material due to the anisotropic charge transport. 相似文献
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Charge transfer in transition‐metal‐dichalcogenides (TMDs) heterostructures is a prerequisite for the formation of interlayer excitons, which hold great promise for optoelectronics and valleytronics. Charge accumulation accompanied by a charge‐transfer process can introduce considerable effect on interlayer exciton‐based applications; nevertheless, this aspect has been rarely studied up to date. This work demonstrates how the charge accumulation affects the light emission of interlayer excitons in van der Waals heterobilayers (HBs) consisting of monolayer WSe2 and WS2. As excitation power increases, the photoluminescence intensity of interlayer excitons increases more rapidly than that of intralayer excitons. The phenomenon can be explained by charge‐accumulation effect, which not only increases the recombination probability of interlayer excitons but also saturates the charge‐transfer process. This scenario is further confirmed by a careful examination of trion binding energy of WS2, which nonlinearly increases with the increase of the excitation power before reaching a maximum of about 75 meV. These investigations provide a better understanding of interlayer excitons and trions in HBs, which may provoke further explorations of excitonic physics as well as TMDs‐based devices. 相似文献
8.
Christian Martella Carlo Mennucci Alessio Lamperti Emmanuele Cappelluti Francesco Buatier de Mongeot Alessandro Molle 《Advanced materials (Deerfield Beach, Fla.)》2018,30(9)
MoS2 and generally speaking, the wide family of transition‐metal dichalcogenides represents a solid nanotechnology platform on which to engineer a wealth of new and outperforming applications involving 2D materials. An even richer flexibility can be gained by extrinsically inducing an in‐plane shape anisotropy of the nanosheets. Here, the synthesis of anisotropic MoS2 nanosheets is proposed as a prototypical example in this respect starting from a highly conformal chemical vapor deposition on prepatterend substrates and aiming at the more general purpose of tailoring anisotropy of 2D nanosheets by design. This is envisioned to be a suitable configuration for strain engineering as far as strain can be spatially redistributed in morphologically different regions. With a similar approach, both the optical and electronic properties of the 2D transition‐metal dichalcogenides can be tailored over macroscopic sample areas in a self‐organized fashion, thus paving the way for new applications in the field of optical metasurfaces, light harvesting, and catalysis. 相似文献
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Yi Rang Lim Jin Kyu Han Yeoheung Yoon Jae‐Bok Lee Cheolho Jeon Min Choi Hyunju Chang Noejung Park Jung Hwa Kim Zonghoon Lee Wooseok Song Sung Myung Sun Sook Lee Ki‐Seok An Jong‐Hyun Ahn Jongsun Lim 《Advanced materials (Deerfield Beach, Fla.)》2019,31(29)
Despite many encouraging properties of transition metal dichalcogenides (TMDs), a central challenge in the realm of industrial applications based on TMD materials is to connect the large‐scale synthesis and reproducible production of highly crystalline TMD materials. Here, the primary aim is to resolve simultaneously the two inversely related issues through the synthesis of MoS2(1?x )Se2x ternary alloys with customizable bichalcogen atomic (S and Se) ratio via atomic‐level substitution combined with a solution‐based large‐area compatible approach. The relative concentration of bichalcogen atoms in the 2D alloy can be effectively modulated by altering the selenization temperature, resulting in 4 in. scale production of MoS1.62Se0.38, MoS1.37Se0.63, MoS1.15Se0.85, and MoS0.46Se1.54 alloys, as well as MoS2 and MoSe2. Comprehensive spectroscopic evaluations for vertical and lateral homogeneity in terms of heteroatom distribution in the large‐scale 2D TMD alloys are implemented. Se‐stimulated strain effects and a detailed mechanism for the Se substitution in the MoS2 crystal are further explored. Finally, the capability of the 2D alloy for industrial application in nanophotonic devices and hydrogen evolution reaction (HER) catalysts is validated. Substantial enhancements in the optoelectronic and HER performances of the 2D ternary alloy compared with those of its binary counterparts, including pure‐phase MoS2 and MoSe2, are unambiguously achieved. 相似文献
10.
Homoepitaxial Growth of Large‐Scale Highly Organized Transition Metal Dichalcogenide Patterns
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Jianyi Chen Xiaoxu Zhao Gustavo Grinblat Zhongxin Chen Sherman J. R. Tan Wei Fu Zijing Ding Ibrahim Abdelwahab Yi Li Dechao Geng Yanpeng Liu Kai Leng Bo Liu Wei Liu Wei Tang Stefan A. Maier Stephen John Pennycook Kian Ping Loh 《Advanced materials (Deerfield Beach, Fla.)》2018,30(4)
Controllable growth of highly crystalline transition metal dichalcogenide (TMD) patterns with regular morphology and unique edge structure is highly desired and important for fundamental research and potential applications. Here, single‐crystalline MoS2 flakes are reported with regular trigonal symmetric patterns that can be homoepitaxially grown on MoS2 monolayer via chemical vapor deposition. The highly organized MoS2 patterns are rhombohedral (3R)‐stacked with the underlying MoS2 monolayer, and their boundaries are predominantly terminated by zigzag Mo edge structure. The epitaxial MoS2 crystals can be tailored from compact triangles to fractal flakes, and the pattern formation can be explained by the anisotropic growth rates of the S and Mo edges under low sulfur chemical potential. The 3R‐stacked MoS2 pattern demonstrates strong second and third‐harmonic‐generation signals, which exceed those reported for monolayer MoS2 by a factor of 6 and 4, correspondingly. This homoepitaxial growth approach for making highly organized TMD patterns is also demonstrated for WS2. 相似文献
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Liang Li Weike Wang Penglai Gong Xiangde Zhu Bei Deng Xingqiang Shi Guoying Gao Huiqiao Li Tianyou Zhai 《Advanced materials (Deerfield Beach, Fla.)》2018,30(14)
Germanium phosphide (GeP), a new member of the Group IV–Group V compounds, is introduced into the fast growing 2D family with experimental and theoretical demonstration of strong anisotropic physical properties. The indirect band gap of GeP can be drastically tuned from 1.68 eV for monolayer to 0.51 eV for bulk, with highly anisotropic dispersions of band structures. Thin GeP shows strong anisotropy of phonon vibrations. Moreover, photodetectors based on GeP flakes show highly anisotropic behavior with anisotropic factors of 1.52 and 1.83 for conductance and photoresponsivity, respectively. This work lays the foundation and ignites future research interests in Group IV–Group V compound 2D materials. 相似文献
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Christian Martella Carlo Mennucci Alessio Lamperti Emmanuele Cappelluti Francesco Buatier de Mongeot Alessandro Molle 《Advanced materials (Deerfield Beach, Fla.)》2017,29(19)
Manipulating the anisotropy in 2D nanosheets is a promising way to tune or trigger functional properties at the nanoscale. Here, a novel approach is presented to introduce a one‐directional anisotropy in MoS2 nanosheets via chemical vapor deposition (CVD) onto rippled patterns prepared on ion‐sputtered SiO2/Si substrates. The optoelectronic properties of MoS2 are dramatically affected by the rippled MoS2 morphology both at the macro‐ and the nanoscale. In particular, strongly anisotropic phonon modes are observed depending on the polarization orientation with respect to the ripple axis. Moreover, the rippled morphology induces localization of strain and charge doping at the nanoscale, thus causing substantial redshifts of the phonon mode frequencies and a topography‐dependent modulation of the MoS2 workfunction, respectively. This study paves the way to a controllable tuning of the anisotropy via substrate pattern engineering in CVD‐grown 2D nanosheets. 相似文献
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One‐Step Solution Phase Growth of Transition Metal Dichalcogenide Thin Films Directly on Solid Substrates
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Anupam Giri Heeseung Yang Kalianan Thiyagarajan Woosun Jang Jae Min Myoung Ranbir Singh Aloysius Soon Kilwon Cho Unyong Jeong 《Advanced materials (Deerfield Beach, Fla.)》2017,29(26)
Ultrathin transition metal dichalcogenides (TMDs) have exotic electronic properties. With success in easy synthesis of high quality TMD thin films, the potential applications will become more viable in electronics, optics, energy storage, and catalysis. Synthesis of TMD thin films has been mostly performed in vacuum or by thermolysis. So far, there is no solution phase synthesis to produce large‐area thin films directly on target substrates. Here, this paper reports a one‐step quick synthesis (within 45–90 s) of TMD thin films (MoS2, WS2, MoSe2, WSe2, etc.) on solid substrates by using microwave irradiation on a precursor‐containing electrolyte solution. The numbers of the quintuple layers of the TMD thin films are precisely controllable by varying the precursor's concentration in the electrolyte solution. A photodetector made of MoS2 thin film comprising of small size grains shows near‐IR absorption, supported by the first principle calculation, exhibits a high photoresponsivity (>300 mA W?1) and a fast response (124 µs). This study paves a robust way for the synthesis of various TMD thin films in solution phases. 相似文献
16.
Rotation‐Misfit‐Free Heteroepitaxial Stacking and Stitching Growth of Hexagonal Transition‐Metal Dichalcogenide Monolayers by Nucleation Kinetics Controls
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Hoseok Heo Ji Ho Sung Gangtae Jin Ji‐Hoon Ahn Kyungwook Kim Myoung‐Jae Lee Soonyoung Cha Hyunyong Choi Moon‐Ho Jo 《Advanced materials (Deerfield Beach, Fla.)》2015,27(25):3803-3810
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Controllable Synthesis of Atomically Thin Type‐II Weyl Semimetal WTe2 Nanosheets: An Advanced Electrode Material for All‐Solid‐State Flexible Supercapacitors
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Peng Yu Wei Fu Qingsheng Zeng Junhao Lin Cheng Yan Zhuangchai Lai Bijun Tang Kazu Suenaga Hua Zhang Zheng Liu 《Advanced materials (Deerfield Beach, Fla.)》2017,29(34)
Compared with 2D S‐based and Se‐based transition metal dichalcogenides (TMDs), Te‐based TMDs display much better electrical conductivities, which will be beneficial to enhance the capacitances in supercapacitors. However, to date, the reports about the applications of Te‐based TMDs in supercapacitors are quite rare. Herein, the first supercapacitor example of the Te‐based TMD is reported: the type‐II Weyl semimetal 1Td WTe2. It is demonstrated that single crystals of 1Td WTe2 can be exfoliated into the nanosheets with 2–7 layers by liquid‐phase exfoliation, which are assembled into air‐stable films and further all‐solid‐state flexible supercapacitors. The resulting supercapacitors deliver a mass capacitance of 221 F g?1 and a stack capacitance of 74 F cm?3. Furthermore, they also show excellent volumetric energy and power densities of 0.01 Wh cm?3 and 83.6 W cm?3, respectively, superior to the commercial 4V/500 µAh Li thin‐film battery and the commercial 3V/300 µAh Al electrolytic capacitor, in association with outstanding mechanical flexibility and superior cycling stability (capacitance retention of ≈91% after 5500 cycles). These results indicate that the 1Td WTe2 nanosheet is a promising flexible electrode material for high‐performance energy storage devices. 相似文献
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Thermodynamically Stable Synthesis of Large‐Scale and Highly Crystalline Transition Metal Dichalcogenide Monolayers and their Unipolar n–n Heterojunction Devices
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Juwon Lee Sangyeon Pak Paul Giraud Young‐Woo Lee Yuljae Cho John Hong A‐Rang Jang Hee‐Suk Chung Woong‐Ki Hong Hu Young Jeong Hyeon Suk Shin Luigi G. Occhipinti Stephen M. Morris SeungNam Cha Jung Inn Sohn Jong Min Kim 《Advanced materials (Deerfield Beach, Fla.)》2017,29(33)
Transition metal dichalcogenide (TMDC) monolayers are considered to be potential materials for atomically thin electronics due to their unique electronic and optical properties. However, large‐area and uniform growth of TMDC monolayers with large grain sizes is still a considerable challenge. This report presents a simple but effective approach for large‐scale and highly crystalline molybdenum disulfide monolayers using a solution‐processed precursor deposition. The low supersaturation level, triggered by the evaporation of an extremely thin precursor layer, reduces the nucleation density dramatically under a thermodynamically stable environment, yielding uniform and clean monolayer films and large crystal sizes up to 500 µm. As a result, the photoluminescence exhibits only a small full‐width‐half‐maximum of 48 meV, comparable to that of exfoliated and suspended monolayer crystals. It is confirmed that this growth procedure can be extended to the synthesis of other TMDC monolayers, and robust MoS2/WS2 heterojunction devices are easily prepared using this synthetic procedure due to the large‐sized crystals. The heterojunction device shows a fast response time (≈45 ms) and a significantly high photoresponsivity (≈40 AW?1) because of the built‐in potential and the majority‐carrier transport at the n–n junction. These findings indicate an efficient pathway for the fabrication of high‐performance 2D optoelectronic devices. 相似文献
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Kuan‐Chang Chiu Kuan‐Hua Huang Chun‐An Chen Ying‐Yu Lai Xin‐Quan Zhang Erh‐Chen Lin Meng‐Hsi Chuang Jenn‐Ming Wu Yi‐Hsien Lee 《Advanced materials (Deerfield Beach, Fla.)》2018,30(7)
Recently, monolayers of van der Waals materials, including transition metal dichalcogenides (TMDs), are considered ideal building blocks for constructing 2D artificial lattices and heterostructures. Heterostructures with multijunctions of more than two monolayer TMDs are intriguing for exploring new physics and materials properties. Obtaining in‐plane heterojunctions of monolayer TMDs with atomically sharp interfaces is very significant for fundamental research and applications. Currently, multistep synthesis for more than two monolayer TMDs remains a challenge because decomposition or compositional alloying is thermodynamically favored at the high growth temperature. Here, a multistep chemical vapor deposition (CVD) synthesis of the in‐plane multijunctions of monolayer TMDs is presented. A low growth temperature synthesis is developed to avoid compositional fluctuations of as‐grown TMDs, defects formations, and interfacial alloying for high heterointerface quality and thermal stability of monolayer TMDs. With optimized parameters, atomically sharp interfaces are successfully achieved in the synthesis of in‐plane artificial lattices of the WS2/WSe2/MoS2 at reduced growth temperatures. Growth behaviors as well as the heterointerface quality are carefully studied in varying growth parameters. Highly oriented strain patterns are found in the second harmonic generation imaging of the TMD multijunctions, suggesting that the in‐plane heteroepitaxial growth may induce distortion for unique material symmetry. 相似文献