On the Stability and Electronic Structure of Transition-Metal Dichalcogenide Monolayer Alloys Mo1−xXxS2−ySey with X = W, Nb
TL;DR: In this paper, the stability and electronic structure of MoS 2 monolayers are influenced by alloying, i.e., by substitution of the transition metal Mo by W and Nb and of the chalcogen S by Se.
Abstract: Layered transition-metal dichalcogenides have extraordinary electronic properties, which can be easily modified by various means. Here, we have investigated how the stability and electronic structure of MoS 2 monolayers is influenced by alloying, i.e., by substitution of the transition metal Mo by W and Nb and of the chalcogen S by Se. While W and Se incorporate into the MoS 2 matrix homogeneously, forming solid solutions, the incorporation of Nb is energetically unstable and results in phase separation. However, all three alloying atoms change the electronic band structure significantly. For example, a very small concentration of Nb atoms introduces localized metallic states, while Mo 1 - x W x S 2 and MoS 2 - y Se y alloys exhibit spin-splitting of the valence band of strength that is in between that of the pure materials. Moreover, small, but evident spin-splitting is introduced in the conduction band due to the symmetry breaking. Therefore, transition-metal dichalcogenide alloys are interesting candidates for optoelectronic and spintronic applications.
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TL;DR: This paper seeks to provide insights for future deployments through a comprehensive performance evaluation that aims to show the strengths and weaknesses of several low-power devices when handling container-virtualized instances.
Abstract: Lightweight virtualization technologies have revolutionized the world of software development by introducing flexibility and innovation to this domain. Although the benefits introduced by these emerging solutions have been widely acknowledged in cloud computing, recent advances have led to the spread of such technologies in different contexts. As an example, the Internet of Things (IoT) and mobile edge computing benefit from container virtualization by exploiting the possibility of using these technologies not only in data centers but also on devices, which are characterized by fewer computational resources, such as single-board computers. This has led to a growing trend to more efficiently redesign the critical components of IoT/edge scenarios (e.g., gateways) to enable the concept of device virtualization. The possibility for efficiently deploying virtualized instances on single-board computers has already been addressed in recent studies; however, these studies considered only a limited number of devices and omitted important performance metrics from their empirical assessments. This paper seeks to fill this gap and to provide insights for future deployments through a comprehensive performance evaluation that aims to show the strengths and weaknesses of several low-power devices when handling container-virtualized instances.
220 citations
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TL;DR: In this paper, a smart sensor network is introduced and the most important features are presented in three different scenarios: a residential home, an industrial installation, and a public building, which demonstrates its capabilities of in situ real-time processing and big-data off-line network processing.
Abstract: Smart meters are one of the basic components of the future smart grid, they allow remotely monitoring each point in the grid in order to know in real-time the performance of the system and to detect potential failures. In this paper, a smart sensor network is introduced and the most important features are presented in three different scenarios: a residential home, an industrial installation, and a public building. The proposed system demonstrates its capabilities of in situ real-time processing and big-data off-line network processing. The suggested smart meter is based on field programmable gate array (FPGA) technology that allows a reconfigurable architecture, which lets the user to select the proper processing modules according to their application. The developed smart sensor network calculates standard figures such as effective values, power factor, and total harmonic distortion; in addition, it detects power quality disturbances such as dips, swells, or interruptions. Moreover, the smart sensor network can continuously detect events to identify certain kind of appliances or industrial equipment such as: fans, lighting, microwave ovens, refrigerators, among others; it is a powerful tool to analyze an entire building in a non-intrusive load monitoring approach.
68 citations
TL;DR: In this paper, a short review summarizes concepts for the development of solution-gated field effect transistors using graphene or related substances as gate material focusing on applications in biosensors.
Abstract: Graphene and graphene-related materials exhibit switchable charge-carrier mobility induced by applying a potential or by interaction with molecules. The short review summarizes concepts for the development of solution-gated field effect transistors using graphene or related substances as gate material focusing on applications in biosensors.
43 citations
TL;DR: In this article, a large-scale synthesis of a uniform monolayer two-dimensional transition metal dichalcogenide (2D TMDCs) nanocrystals by controlling their composition or structure is considered to be an important method of tailoring light absorption, electron transition and carrier mobility.
Abstract: Tuning the bandgap of thin-layered two-dimensional transition metal dichalcogenide (2D TMDCs) nanocrystals by controlling their composition or structure is considered to be an important method of tailoring light absorption, electron transition and carrier mobility. However, the large-scale synthesis of TMDs with a tunable bandgap on graphene remains challenging owing to the difficulty in controlling the uniformity of the layer thickness. Herein, we report the large-area synthesis of a uniform monolayer MoS2(1−x)Se2x film on a monolayer graphene using low-pressure chemical vapour deposition to realize a 2D heterostructure. The resultant centimetre-scale monolayer MoS2(1−x)Se2x film on graphene showed a highly crystalline structure and a tunable bandgap from 1.82 eV to 1.66 eV, which could be controlled by tuning the atomic ratio of S to Se. A phototransistor with the MoS2(1−x)Se2x/graphene heterostructure exhibited a high responsivity of 40.64 mA W−1 under light irradiation of 465 nm with good stability up to 50 cycles. A high photocurrent arose from the efficient charge transfer from MoS2(1−x)Se2x to graphene with a high carrier mobility based on the good electronic interaction. Thus, the large-scale high-quality bandgap-tunable MoS2(1−x)Se2x/graphene heterostructure with controllable structures and electronic properties could be developed and integrated into advanced optoelectronic devices.
35 citations
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TL;DR: A simple derivation of a simple GGA is presented, in which all parameters (other than those in LSD) are fundamental constants, and only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked.
Abstract: Generalized gradient approximations (GGA’s) for the exchange-correlation energy improve upon the local spin density (LSD) description of atoms, molecules, and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental constants. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential. [S0031-9007(96)01479-2] PACS numbers: 71.15.Mb, 71.45.Gm Kohn-Sham density functional theory [1,2] is widely used for self-consistent-field electronic structure calculations of the ground-state properties of atoms, molecules, and solids. In this theory, only the exchange-correlation energy EXC › EX 1 EC as a functional of the electron spin densities n"srd and n#srd must be approximated. The most popular functionals have a form appropriate for slowly varying densities: the local spin density (LSD) approximation Z d 3 rn e unif
146,533 citations
"On the Stability and Electronic Str..." refers methods in this paper
...The exchange and correlation terms were described using general gradient approximation (GGA) in the scheme of the PBE (Perdew–Burke–Ernzerhof) [32] functional....
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TL;DR: In this article, a method for generating sets of special points in the Brillouin zone which provides an efficient means of integrating periodic functions of the wave vector is given, where the integration can be over the entire zone or over specified portions thereof.
Abstract: A method is given for generating sets of special points in the Brillouin zone which provides an efficient means of integrating periodic functions of the wave vector. The integration can be over the entire Brillouin zone or over specified portions thereof. This method also has applications in spectral and density-of-state calculations. The relationships to the Chadi-Cohen and Gilat-Raubenheimer methods are indicated.
51,059 citations
TL;DR: The electronic properties of ultrathin crystals of molybdenum disulfide consisting of N=1,2,…,6 S-Mo-S monolayers have been investigated by optical spectroscopy and the effect of quantum confinement on the material's electronic structure is traced.
Abstract: The electronic properties of ultrathin crystals of molybdenum disulfide consisting of N=1,2,…,6 S-Mo-S monolayers have been investigated by optical spectroscopy Through characterization by absorption, photoluminescence, and photoconductivity spectroscopy, we trace the effect of quantum confinement on the material's electronic structure With decreasing thickness, the indirect band gap, which lies below the direct gap in the bulk material, shifts upwards in energy by more than 06 eV This leads to a crossover to a direct-gap material in the limit of the single monolayer Unlike the bulk material, the MoS₂ monolayer emits light strongly The freestanding monolayer exhibits an increase in luminescence quantum efficiency by more than a factor of 10⁴ compared with the bulk material
12,822 citations
TL;DR: This observation shows that quantum confinement in layered d-electron materials like MoS(2), a prototypical metal dichalcogenide, provides new opportunities for engineering the electronic structure of matter at the nanoscale.
Abstract: Novel physical phenomena can emerge in low-dimensional nanomaterials. Bulk MoS2, a prototypical metal dichalcogenide, is an indirect bandgap semiconductor with negligible photoluminescence. When the MoS2 crystal is thinned to monolayer, however, a strong photoluminescence emerges, indicating an indirect to direct bandgap transition in this d-electron system. This observation shows that quantum confinement in layered d-electron materials like MoS2 provides new opportunities for engineering the electronic structure of matter at the nanoscale.
7,886 citations
TL;DR: The transition metal dichalcogenides are about 60 in number as discussed by the authors, and two-thirds of these assume layer structures and can be cleaved down to less than 1000 A and are then transparent in the region of direct band-to-band transitions.
Abstract: The transition metal dichalcogenides are about 60 in number. Two-thirds of these assume layer structures. Crystals of such materials can be cleaved down to less than 1000 A and are then transparent in the region of direct band-to-band transitions. The transmission spectra of the family have been correlated group by group with the wide range of electrical and structural data available to yield useful working band models that are in accord with a molecular orbital approach. Several special topics have arisen; these include exciton screening, d-band formation, and the metal/insulator transition; also magnetism and superconductivity in such compounds. High pressure work seems to offer the possibility for testing the recent theory of excitonic insulators.
3,313 citations