scholarly journals Enhancing monolayer photoluminescence on optical micro/nanofibers for low-threshold lasing

2019 ◽  
Vol 5 (11) ◽  
pp. eaax7398 ◽  
Author(s):  
Feng Liao ◽  
Jiaxin Yu ◽  
Zhaoqi Gu ◽  
Zongyin Yang ◽  
Tawfique Hasan ◽  
...  
Keyword(s):  
Room Temperature ◽  
Dynamic Range ◽  
Transition Metal Dichalcogenides ◽  
Pump Intensity ◽  
Environmental Stability ◽  
Quantum Yields ◽  
Light Emitters ◽  
Practical Applications ◽  
Metal Dichalcogenides ◽  
High Pump

Although monolayer transition metal dichalcogenides (TMDs) have direct bandgaps, the low room-temperature photoluminescence quantum yields (QYs), especially under high pump intensity, limit their practical applications. Here, we use a simple photoactivation method to enhance the room-temperature QYs of monolayer MoS2 grown on to silica micro/nanofibers by more than two orders of magnitude in a wide pump dynamic range. The high-density oxygen dangling bonds released from the tapered micro/nanofiber surface are the key to this strong enhancement of QYs. As the pump intensity increases from 10−1 to 104 W cm−2, our photoactivated monolayer MoS2 exhibits QYs from ~30 to 1% while maintaining high environmental stability, allowing direct lasing with greatly reduced thresholds down to 5 W cm−2. Our strategy can be extended to other TMDs and offers a solution to the most challenging problem toward the realization of efficient and stable light emitters at room temperature based on these atomically thin materials.

Design, simulation and optimization of multi-layered MoS2 based FET devices

2021 ◽  
Author(s):  
Agraj Khare ◽  
Priyanka Dwivedi
Keyword(s):  
Dynamic Range ◽  
Field Effect Transistors ◽  
Electronic Devices ◽  
Transition Metal Dichalcogenides ◽  
Wave Model ◽  
Threshold Potential ◽  
Simulation And Optimization ◽  
Full Wave ◽  
Emerging Trends ◽  
Metal Dichalcogenides

Abstract Transition-metal Dichalcogenides (TMDs) materials are getting attention in the emerging trends of electronic devices development for a variety of applications. One of such materials is MoS2 which is best suited for developing deeply scaled field effect transistors (FETs). With the plethora of TMDs available, MoS2 is the most widely studied and used material because of its tunable properties like band gap, morphology, optical, structural, electrical, flexible etc. This paper represents the design and simulation aspect of the multi-layered MoS2 Based FET devices. Evidence of change in comparative electrical characteristics of MoS2 based FET devices due to variation of thickness and doping of the gate layer are also presented. In this contribution, we have simulated a full-wave model using the COMSOL Multiphysics module for two different thicknesses 0.7 nm and 1 nm. The FET device with 1 nm MoS2 offers a better dynamic range of operation and has a broader spectrum of threshold potential. The characteristic plots of the 1 nm device showed very less deviation from ideal trends than in the 0.7 nm device. The optimized FET structure offers better performance and efficiency in terms of electrical properties.

scholarly journals Measurement of Quantum Yields of Monolayer TMDs Using Dye-Dispersed PMMA Thin Films

Nanomaterials ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 1032 ◽  
Author(s):  
Shrawan Roy ◽  
Anir S. Sharbirin ◽  
Yongjun Lee ◽  
Won Bin Kim ◽  
Tae Soo Kim ◽  
...  
Keyword(s):  
Vapor Deposition ◽  
Rhodamine 6G ◽  
Composite Films ◽  
Transition Metal Dichalcogenides ◽  
Chemical Vapor ◽  
Quantum Yields ◽  
Simple Protocol ◽  
Metal Dichalcogenides ◽  
Spatially Homogeneous ◽  
Reference Specimens

In general, the quantum yields (QYs) of monolayer transition metal dichalcogenides (1L-TMDs) are low, typically less than 1% in their pristine state, significantly limiting their photonic applications. Many methods have been reported to increase the QYs of 1L-TMDs; however, the technical difficulties involved in the reliable estimation of these QYs have prevented the general assessment of these methods. Herein, we demonstrate the estimation of the QYs of 1L-TMDs using a poly methyl methacrylate (PMMA) thin film embedded with rhodamine 6G (R6G) as a reference specimen for measuring the QYs of 1L-TMDs. The PMMA/R6G composite films with thicknesses of 80 and 300 nm demonstrated spatially homogeneous emissions with the incorporation of well-dispersed R6G molecules, and may, therefore, be used as ideal reference specimens for the QY measurement of 1L-TMDs. Using our reference specimens, for which the QY ranged from 5.4% to 22.2% depending on the film thickness and R6G concentrations, we measured the QYs of the exfoliated or chemical vapor deposition (CVD)-grown 1L-WS2, -MoSe2, -MoS2, and -WSe2 TMDs. The convenient procedure proposed in this study for preparing the thin reference films and the simple protocol for the QY estimation of 1L-TMDs may enable accurate comparisons of the absolute QYs between the 1L-TMD samples, thereby enabling the development of a method to improve the QY of 1L-TMDs.

scholarly journals Intrinsic lifetime of higher excitonic states in tungsten diselenide monolayers

Nanoscale ◽  
2019 ◽  
Vol 11 (25) ◽  
pp. 12381-12387 ◽  
Author(s):  
Samuel Brem ◽  
Jonas Zipfel ◽  
Malte Selig ◽  
Archana Raja ◽  
Lutz Waldecker ◽  
...  
Keyword(s):  
Transition Metal ◽  
Room Temperature ◽  
Transition Metal Dichalcogenides ◽  
Optical Spectra ◽  
Tungsten Diselenide ◽  
Dielectric Screening ◽  
Metal Dichalcogenides ◽  
Excitonic States

The reduced dielectric screening in atomically thin transition metal dichalcogenides allows to study the hydrogen-like series of higher exciton states in optical spectra even at room temperature.

scholarly journals Exciton–phonon coupling strength in single-layer MoSe2 at room temperature

2020 ◽  
Author(s):  
Donghai Li ◽  
Chiara Trovatello ◽  
Stefano Dal Conte ◽  
Matthias Nuß ◽  
Giancarlo Soavi ◽  
...  
Keyword(s):  
Room Temperature ◽  
Research Effort ◽  
Transition Metal Dichalcogenides ◽  
Optoelectronic Devices ◽  
Single Layer ◽  
Semiconductor Nanostructures ◽  
Phonon Coupling ◽  
Layer Transition ◽  
Fundamental Physics ◽  
Metal Dichalcogenides

Abstract Single-layer transition metal dichalcogenides (1L-TMDs) are at the center of an ever increasing research effort both in terms of fundamental physics and applications. Exciton–phonon coupling (EXPC) plays a key role in determining the photonic and (opto)electronic properties of 1L-TMDs. However, the EXPC strength has not been measured at room temperature. Here, we develop two-dimensional (2D) micro-spectroscopy to determine EXPC of 1L-MoSe2. We detect beating signals as a function of waiting time T, induced by the coupling between the A exciton and the A'1 optical phonon. Analysis of 2D beating maps provides the EXPC with the help of simulations. The Huang–Rhys factor of ~1 is larger than in most other inorganic semiconductor nanostructures. Our technique offers a unique tool to measure EXPC also in other 1L-TMDs and heterogeneous semiconducting systems with a spatial resolution ~260 nm, and will provide design-relevant parameters for the development of novel optoelectronic devices.

The Role of Two-Dimensional Materials in Electromagnetic Interference Shielding

2021 ◽  
pp. 1254-1270
Author(s):  
Rafael Vargas-Bernal
Keyword(s):  
Electromagnetic Interference ◽  
Transition Metal Dichalcogenides ◽  
Environmental Stability ◽  
Two Dimensional ◽  
Shielding Effectiveness ◽  
Electromagnetic Interference Shielding ◽  
Two Dimensional Materials ◽  
Metal Dichalcogenides ◽  
Materials Used ◽  
The Impact

Commonly, metallic materials are used in practical ways to increase the shielding effectiveness (SE) through an appropriately designed assembly process. Unfortunately, the high density of devices that require it and the poor environmental stability of metals have impeded their massive use. In addition, for applications in the automotive, aerospace, and electronics industries, materials with light weight and good chemical stability are also required. The purpose of this chapter is to describe the impact that two-dimensional materials (or 2D materials) are having on the development of materials used for electromagnetic interference shielding, particularly the impulse of materials such as graphene, MXenes, transition metal dichalcogenides (TMDs), and phosphorene. The advances in the last decade are analyzed and alternatives are proposed that will come in the next decades. The shielding mechanisms presented by the two-dimensional materials are analyzed in detail and the specific applications in which these materials can be used are presented.

scholarly journals Valley-Selective Response of Nanostructures Coupled to 2D Transition-Metal Dichalcogenides

2018 ◽  
Vol 8 (7) ◽  
pp. 1157 ◽  
Author(s):  
Alexander Krasnok ◽  
Andrea Alù
Keyword(s):  
Transition Metal ◽  
Room Temperature ◽  
State Of The Art ◽  
Transition Metal Dichalcogenides ◽  
Zone Boundary ◽  
Brillouin Zone Boundary ◽  
Directional Emission ◽  
Metal Dichalcogenides ◽  
On Chip ◽  
Valley Hall Effect

Monolayer (1L) transition-metal dichalcogenides (TMDCs) are attractive materials for several optoelectronic applications because of their strong excitonic resonances and valley-selective response. Valley excitons in 1L-TMDCs are formed at opposite points of the Brillouin zone boundary, giving rise to a valley degree of freedom that can be treated as a pseudospin, and may be used as a platform for information transport and processing. However, short valley depolarization times and relatively short exciton lifetimes at room temperature prevent using valley pseudospins in on-chip integrated valley devices. Recently, it was demonstrated how coupling these materials to optical nanoantennas and metasurfaces can overcome this obstacle. Here, we review the state-of-the-art advances in valley-selective directional emission and exciton sorting in 1L-TMDC mediated by nanostructures and nanoantennas. We briefly discuss the optical properties of 1L-TMDCs paying special attention to their photoluminescence/absorption spectra, dynamics of valley depolarization, and the valley Hall effect. Then, we review recent works on nanostructures for valley-selective directional emission from 1L-TMDCs.

scholarly journals Room Temperature Terahertz Electroabsorption Modulation by Excitons in Monolayer Transition Metal Dichalcogenides

Nano Letters ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 5214-5220
Author(s):  
Jiaojian Shi ◽  
Edoardo Baldini ◽  
Simone Latini ◽  
Shunsuke A. Sato ◽  
Yaqing Zhang ◽  
...  
Keyword(s):  
Transition Metal ◽  
Room Temperature ◽  
Transition Metal Dichalcogenides ◽  
Metal Dichalcogenides

scholarly journals The Interaction of Hydrogen with the van der Waals Crystal γ-InSe

Molecules ◽  
2020 ◽  
Vol 25 (11) ◽  
pp. 2526 ◽  
Author(s):  
James Felton ◽  
Elena Blundo ◽  
Sanliang Ling ◽  
Joseph Glover ◽  
Zakhar R. Kudrynskyi ◽  
...  
Keyword(s):  
Density Functional ◽  
Room Temperature ◽  
Theoretical Study ◽  
Van Der Waals ◽  
Transition Metal Dichalcogenides ◽  
Ion Source ◽  
Vibrational Modes ◽  
Functional Theory ◽  
Metal Dichalcogenides ◽  
Experimental And Theoretical Studies

The emergence of the hydrogen economy requires development in the storage, generation and sensing of hydrogen. The indium selenide ( γ -InSe) van der Waals (vdW) crystal shows promise for technologies in all three of these areas. For these applications to be realised, the fundamental interactions of InSe with hydrogen must be understood. Here, we present a comprehensive experimental and theoretical study on the interaction of γ -InSe with hydrogen. It is shown that hydrogenation of γ -InSe by a Kaufman ion source results in a marked quenching of the room temperature photoluminescence signal and a modification of the vibrational modes of γ -InSe, which are modelled by density functional theory simulations. Our experimental and theoretical studies indicate that hydrogen is incorporated into the crystal preferentially in its atomic form. This behaviour is qualitatively different from that observed in other vdW crystals, such as transition metal dichalcogenides, where molecular hydrogen is intercalated in the vdW gaps of the crystal, leading to the formation of “bubbles” for hydrogen storage.

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