Special Issue "Two-Dimensional Transition Metal Dichalcogenides"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Chemistry".

Deadline for manuscript submissions: closed (31 July 2016).

Special Issue Editor

Dr. Andres Castellanos-Gomez
grade E-Mail Website
Guest Editor
CSIC - Instituto de Ciencia de Materiales de Madrid (ICMM), Materials Science Factory, Cantoblanco, 28049 Madrid, Spain
Interests: two-dimensional materials; nanomechanics; strain-engineering; optoelectronics; molybdenum disulfide (MoS2); transition metal dichalcogenides; black phosphorus
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Special Issue Information

Dear Colleagues,

The isolation of graphene opened the gate to a vast field devoted to the study of inorganic two-dimensional materials. Among the different two-dimensional materials beyond graphene, the family of transition metal dichalcogenides has recently attracted the interest of the scientific community as a large variety of electronic behaviors, ranging from wide band gap semiconductors to superconductors, is exhibited by the different members of this large family of two-dimensional materials.

This Special Issue aims to cover the entire range of fundamental, applied and practical subjects associated with the synthesis, characterization and development of transition metal dichalcogenide-based devices.

Dr. Andres Castellanos-Gomez
Guest Editor

Manuscript Submission Information

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Keywords

  • Transition metal dichalcogenides
  • Molybdenum disulfide MoS2
  • Molybdenum diselenide MoSe2
  • Tungsten disulfide WS2
  • Tungsten diselenide WSe2
  • Niobium diselenide NbSe2
  • Rhenium disulfide ReS2
  • Rhenium diselenide ReSe2
  • Tantalum disulfide TaS2
  • Tantalum diselenide TaSe2
  • Hafnium disulfide HfS2
  • Hafnium diselenide HfSe2
  • Properties: electronic, optical, thermal, mechanical
  • Optoelectronics
  • Thermoelectrics
  • Nanodevices
  • Nano-electromechanical systems

Published Papers (6 papers)

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Research

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Article
Electronic Band Structure of Transition Metal Dichalcogenides from Ab Initio and Slater–Koster Tight-Binding Model
Appl. Sci. 2016, 6(10), 284; https://0-doi-org.brum.beds.ac.uk/10.3390/app6100284 - 01 Oct 2016
Cited by 32 | Viewed by 5872
Abstract
Semiconducting transition metal dichalcogenides present a complex electronic band structure with a rich orbital contribution to their valence and conduction bands. The possibility to consider the electronic states from a tight-binding model is highly useful for the calculation of many physical properties, for [...] Read more.
Semiconducting transition metal dichalcogenides present a complex electronic band structure with a rich orbital contribution to their valence and conduction bands. The possibility to consider the electronic states from a tight-binding model is highly useful for the calculation of many physical properties, for which first principle calculations are more demanding in computational terms when having a large number of atoms. Here, we present a set of Slater–Koster parameters for a tight-binding model that accurately reproduce the structure and the orbital character of the valence and conduction bands of single layer MX 2 , where M = Mo, W and X = S, Se. The fit of the analytical tight-binding Hamiltonian is done based on band structure from ab initio calculations. The model is used to calculate the optical conductivity of the different compounds from the Kubo formula. Full article
(This article belongs to the Special Issue Two-Dimensional Transition Metal Dichalcogenides)
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Communication
Raman Spectra of ZrS2 and ZrSe2 from Bulk to Atomically Thin Layers
Appl. Sci. 2016, 6(9), 264; https://0-doi-org.brum.beds.ac.uk/10.3390/app6090264 - 15 Sep 2016
Cited by 39 | Viewed by 6113
Abstract
In the race towards two-dimensional electronic and optoelectronic devices, semiconducting transition metal dichalcogenides (TMDCs) from group VIB have been intensively studied in recent years due to the indirect to direct band-gap transition from bulk to the monolayer. However, new materials still need to [...] Read more.
In the race towards two-dimensional electronic and optoelectronic devices, semiconducting transition metal dichalcogenides (TMDCs) from group VIB have been intensively studied in recent years due to the indirect to direct band-gap transition from bulk to the monolayer. However, new materials still need to be explored. For example, semiconducting TMDCs from group IVB have been predicted to have larger mobilities than their counterparts from group VIB in the monolayer limit. In this work we report the mechanical exfoliation of ZrX2 (X = S, Se) from bulk down to the monolayer and we study the dimensionality dependence of the Raman spectra in ambient conditions. We observe Raman signal from bulk to few layers and no shift in the peak positions is found when decreasing the dimensionality. While a Raman signal can be observed from bulk to a bilayer for ZrS2, we could only detect signal down to five layers for flakes of ZrSe2. These results show the possibility of obtaining atomically thin layers of ZrX2 by mechanical exfoliation and represent one of the first steps towards the investigation of the properties of these materials, still unexplored in the two-dimensional limit. Full article
(This article belongs to the Special Issue Two-Dimensional Transition Metal Dichalcogenides)
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Article
Local Oxidation Nanolithography on Metallic Transition Metal Dichalcogenides Surfaces
Appl. Sci. 2016, 6(9), 250; https://0-doi-org.brum.beds.ac.uk/10.3390/app6090250 - 08 Sep 2016
Cited by 7 | Viewed by 3593
Abstract
The integration of atomically-thin layers of two dimensional (2D) materials in nanodevices demands for precise techniques at the nanoscale permitting their local modification, structuration or resettlement. Here, we present the use of Local Oxidation Nanolithography (LON) performed with an Atomic Force Microscope (AFM) [...] Read more.
The integration of atomically-thin layers of two dimensional (2D) materials in nanodevices demands for precise techniques at the nanoscale permitting their local modification, structuration or resettlement. Here, we present the use of Local Oxidation Nanolithography (LON) performed with an Atomic Force Microscope (AFM) for the patterning of nanometric motifs on different metallic Transition Metal Dichalcogenides (TMDCs). We show the results of a systematic study of the parameters that affect the LON process as well as the use of two different modes of lithographic operation: dynamic and static. The application of this kind of lithography in different types of TMDCs demonstrates the versatility of the LON for the creation of accurate and reproducible nanopatterns in exfoliated 2D-crystals and reveals the influence of the chemical composition and crystalline structure of the systems on the morphology of the resultant oxide motifs. Full article
(This article belongs to the Special Issue Two-Dimensional Transition Metal Dichalcogenides)
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Article
The Positive Effects of Hydrophobic Fluoropolymers on the Electrical Properties of MoS2 Transistors
Appl. Sci. 2016, 6(9), 236; https://0-doi-org.brum.beds.ac.uk/10.3390/app6090236 - 23 Aug 2016
Cited by 2 | Viewed by 3419
Abstract
We report the improvement of the electrical performance of field effect transistors (FETs) fabricated on monolayer chemical vapor deposited (CVD) MoS2, by applying an interacting fluoropolymer capping layer (Teflon-AF). The electrical characterizations of more than 60 FETs, after applying Teflon-AF cap, [...] Read more.
We report the improvement of the electrical performance of field effect transistors (FETs) fabricated on monolayer chemical vapor deposited (CVD) MoS2, by applying an interacting fluoropolymer capping layer (Teflon-AF). The electrical characterizations of more than 60 FETs, after applying Teflon-AF cap, show significant improvement of the device properties and reduced device to device variation. The improvement includes: 50% reduction of the average gate hysteresis, 30% reduction of the subthreshold swing and about an order of magnitude increase of the current on-off ratio. These favorable changes in device performance are attributed to the reduced exposure of MoS2 channels to the adsorbates in the ambient which can be explained by the polar nature of Teflon-AF cap. A positive shift in the threshold voltage of all the measured FETs is observed, which translates to the more desirable enhancement mode transistor characteristics. Full article
(This article belongs to the Special Issue Two-Dimensional Transition Metal Dichalcogenides)
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Article
Optical and Transport Properties of Ni-MoS2
Appl. Sci. 2016, 6(8), 227; https://0-doi-org.brum.beds.ac.uk/10.3390/app6080227 - 12 Aug 2016
Cited by 5 | Viewed by 2428
Abstract
In this paper, MoS2 and Ni-MoS2 crystal layers were fabricated by the chemical vapor transport method with iodine as the transport agent. Two direct band edge transitions of excitons at 1.9 and 2.1 eV were observed successfully for both MoS2 [...] Read more.
In this paper, MoS2 and Ni-MoS2 crystal layers were fabricated by the chemical vapor transport method with iodine as the transport agent. Two direct band edge transitions of excitons at 1.9 and 2.1 eV were observed successfully for both MoS2 and Ni-MoS2 samples using temperature-dependent optical reflectance (R) measurement. Hall effect measurements were carried out to analyze the transport behavior of carriers in MoS2 and Ni-MoS2, which indicate that the Ni-MoS2 sample is n-type and has a higher resistance and lower mobility than the MoS2 sample has. A photoconductivity spectrum was performed which shows an additional Ni doping level existing at 1.2 eV and a higher photocurrent generating only for Ni-MoS2. The differences between MoS2 and Ni-MoS2 could be attributed to the effect of Ni atoms causing small lattice imperfections to form trap states around 1.2 eV. The temperature-dependent conductivity shows the presence of two shallow levels with activation energies (84 and 6.7 meV in MoS2; 57 and 6.5 meV in Ni-MoS2). Therefore, the Ni doping level leads to high resistance, low mobility and small activation energies. A series of experimental results could provide useful guidance for the fabrication of optoelectronic devices using MoS2 structures. Full article
(This article belongs to the Special Issue Two-Dimensional Transition Metal Dichalcogenides)
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Review

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Review
Optoelectronic Devices Based on Atomically Thin Transition Metal Dichalcogenides
Appl. Sci. 2016, 6(3), 78; https://0-doi-org.brum.beds.ac.uk/10.3390/app6030078 - 10 Mar 2016
Cited by 80 | Viewed by 6227
Abstract
We review the application of atomically thin transition metal dichalcogenides in optoelectronic devices. First, a brief overview of the optical properties of two-dimensional layered semiconductors is given and the role of excitons and valley dichroism in these materials are discussed. The following sections [...] Read more.
We review the application of atomically thin transition metal dichalcogenides in optoelectronic devices. First, a brief overview of the optical properties of two-dimensional layered semiconductors is given and the role of excitons and valley dichroism in these materials are discussed. The following sections review and compare different concepts of photodetecting and light emitting devices, nanoscale lasers, single photon emitters, valleytronics devices, as well as photovoltaic cells. Lateral and vertical device layouts and different operation mechanisms are compared. An insight into the emerging field of valley-based optoelectronics is given. We conclude with a critical evaluation of the research area, where we discuss potential future applications and remaining challenges. Full article
(This article belongs to the Special Issue Two-Dimensional Transition Metal Dichalcogenides)
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