7,324 research outputs found

    Transition Metal Dichalcogenide Photodetectors

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    Two Dimensional (2D) materials has triggered to have transition metal dichalcogenides (TMDCs) emerging as a new class of materials that can control or interact with light to convert the photons to electrical signals for its attractive applications in photonics, electronics and optoelectronics. 2D materials along with gapless Graphene interact with light over the wavelength region of the different spectral regions having the short wavelength of the UV and extreme UV, Visible, near IR, mid IR and THz due to excellent light absorption, enabling ultrafast and ultrasensitive detection of light in photodetectors. Next generation photodetectors are possible promising candidates for high sensitivity and TMDCs based photodetectors are the heart of the multitude of technologies to understand the principle of photodetection mechanisms and device performances. Phototransistors/photoconductors show wide varied detection performances with responsivities ranging from 10−7 A/W - 107 A/W on single or few layer TMDCs having response time between 10−5 s to 103 s. The semiconducting TMDCs like MoS2, MoSe2, WS2, WSe2 and ReS2 are gaining suitable applications in optoelectronic devices and the device design, mechanism and enhancing the performance of photodetectors are introduced and discussed systematically in this chapter. In spite of the growing demands on TMDC based devices the origin of the photoresponse characteristics is attractive and encouraging to understand and provide a path to the subject of investigation and guidelines for the future development of this rapidly growing field

    Phonon chirality manipulation mechanism in TMD interlayer-sliding ferroelectrics

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    As an ideal platform, both the theoretical prediction and first experimental verification of chiral phonons are based on transition-metal dichalcogenide materials. The manipulation of phonon chirality in these materials will have a profound impact on the study of chiral phonons. In this work, we utilize the sliding ferroelectric mechanism to study the phonon chirality manipulation mechanism in transition-metal dichalcogenide materials. Based on first-principles calculations, we study the different effects of interlayer sliding on the phonon properties in bilayer and four-layer MoS2_2 sliding ferroelectrics. We find that sliding can regulate phonon chirality and Berry curvature, which further affects the phonon angular momentum and magnetization under a temperature gradient and the phonon Hall effect under a magnetic field. Our work connects two emerging fields and opens up a new route to manipulate phonon chirality in transition-metal dichalcogenide materials through the sliding ferroelectric mechanism.Comment: 15 pages, 4 figure

    Noncollinear exchange interaction in transition metal dichalcogenide edges

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    We study the Ruderman-Kittel-Kasuya-Yosida effective exchange interaction between magnetic impurities embedded on the edges of transition-metal dichalcogenide flakes, using a three-orbital tight-binding model. Electronic states lying midgap of the bulk structure have strong one-dimensional (1D) character, localized on the edges of the crystallite. This results in exchange interactions with 1/r1/r (or slower) decay with distance rr, similar to other 1D systems. Most interestingly, however, the strong spin-orbit interaction in these materials results in sizable non-collinear Dzyaloshinskii-Moriya interactions between impurities, comparable in size to the usual Ising and in-plane components. Varying the relevant Fermi energy by doping or gating may allow one to modulate the effective interactions, controlling the possible helical ground state configurations of multiple impurities.Comment: 5 pages and 4 figure

    Exciton-exciton interaction in transition-metal dichalcogenide monolayers

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    We study theoretically the Coulomb interaction between excitons in transition metal dichalcogenide (TMD) monolayers. We calculate direct and exchange interaction for both ground and excited states of excitons. The screening of the Coulomb interaction, specific to monolayer structures, leads to the unique behavior of the exciton-exciton scattering for excited states, characterized by the non-monotonic dependence of the interaction as function of the transferred momentum. We find that the nontrivial screening enables the description of TMD exciton interaction strength by approximate formula which includes exciton binding parameters. The influence of screening and dielectric environment on the exciton-exciton interaction was studied, showing qualitatively different behavior for ground state and excited states of excitons. Furthermore, we consider exciton-electron interaction, which for the excited states is governed by the dominant attractive contribution of the exchange component, which increases with the excitation number. The results provide a quantitative description of the exciton-exciton and exciton-electron scattering in transition metal dichalcogenides, and are of interest for the design of perspective nonlinear optical devices based on TMD monolayers.Comment: 10 pages, 6 figure
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