Journal articles: 'TMDC materials'

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Huang, Lujun, Alex Krasnok, Andrea Alú, Yiling Yu, Dragomir Neshev, and Andrey E. Miroshnichenko. "Enhanced light–matter interaction in two-dimensional transition metal dichalcogenides." Reports on Progress in Physics 85, no. 4 (March 8, 2022): 046401. http://dx.doi.org/10.1088/1361-6633/ac45f9.

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Abstract Two-dimensional (2D) transition metal dichalcogenide (TMDC) materials, such as MoS2, WS2, MoSe2, and WSe2, have received extensive attention in the past decade due to their extraordinary electronic, optical and thermal properties. They evolve from indirect bandgap semiconductors to direct bandgap semiconductors while their layer number is reduced from a few layers to a monolayer limit. Consequently, there is strong photoluminescence in a monolayer (1L) TMDC due to the large quantum yield. Moreover, such monolayer semiconductors have two other exciting properties: large binding energy of excitons and valley polarization. These properties make them become ideal materials for various electronic, photonic and optoelectronic devices. However, their performance is limited by the relatively weak light–matter interactions due to their atomically thin form factor. Resonant nanophotonic structures provide a viable way to address this issue and enhance light–matter interactions in 2D TMDCs. Here, we provide an overview of this research area, showcasing relevant applications, including exotic light emission, absorption and scattering features. We start by overviewing the concept of excitons in 1L-TMDC and the fundamental theory of cavity-enhanced emission, followed by a discussion on the recent progress of enhanced light emission, strong coupling and valleytronics. The atomically thin nature of 1L-TMDC enables a broad range of ways to tune its electric and optical properties. Thus, we continue by reviewing advances in TMDC-based tunable photonic devices. Next, we survey the recent progress in enhanced light absorption over narrow and broad bandwidths using 1L or few-layer TMDCs, and their applications for photovoltaics and photodetectors. We also review recent efforts of engineering light scattering, e.g., inducing Fano resonances, wavefront engineering in 1L or few-layer TMDCs by either integrating resonant structures, such as plasmonic/Mie resonant metasurfaces, or directly patterning monolayer/few layers TMDCs. We then overview the intriguing physical properties of different van der Waals heterostructures, and their applications in optoelectronic and photonic devices. Finally, we draw our opinion on potential opportunities and challenges in this rapidly developing field of research.

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Tao, Guang-Yi, Peng-Fei Qi, Yu-Chen Dai, Bei-Bei Shi, Yi-Jing Huang, Tian-Hao Zhang, and Zhe-Yu Fang. "Enhancement of photoluminescence of monolayer transition metal dichalcogenide by subwavelength TiO2 grating." Acta Physica Sinica 71, no. 8 (2022): 087801. http://dx.doi.org/10.7498/aps.71.20212358.

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Monolayer transition metal dichalcogenide (TMDC) has a direct band gap and can produce strong photoluminescence(PL), thereby possessing a wide application prospect in photoelectric devices and photoelectric detection fields. However, its PL efficiency needs further improving because its monolayer is of atomic thickness only, besides, it has non-radiative recombination of excitons. In this study, a combination structure of a gold film, titanium dioxide subwavelength gratings and monolayer TMDCs is designed, which can greatly improve PL efficiency of monolayer TMDC. The spontaneous emission rate can be controlled by the Purcell effect, and the maximum enhancement of photoluminescence is as high as 3.4 times. In this paper, the PL signal of monolayer WS2 and monolayer WSe2 on the designed structure are studied. The feasibility of the enhancement of PL of monolayer TMDC in the coupling structure of monolayer TMDC and the subwavelength grating is verified experimentally, which provides a new idea for the application of two-dimensional materials to optoelectronic devices.

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Zhang, Yudong, Yukun Chen, Min Qian, Haifen Xie, and Haichuan Mu. "Chemical vapor deposited WS₂/MoS₂ heterostructure photodetector with enhanced photoresponsivity." Journal of Physics D: Applied Physics 55, no. 17 (January 31, 2022): 175101. http://dx.doi.org/10.1088/1361-6463/ac4cf7.

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Abstract Two-dimensional transition metal dichalcogenides (TMDCs) have attracted great interest due to their unique semiconductor properties. Among all TMDC materials, MoS2 and WS2 are promising for composing heterostructures. However, traditional TMDC heterostructure fabrication depends on transfer process, with drawbacks of interface impurity and small size. In this work, a two-step chemical vapor deposition (CVD) process was applied to synthesize large-scale WS2/MoS2 heterostructure. Surface morphology and crystal structure characterizations demonstrate the high-quality WS2/MoS2 heterostructure. The WS2/MoS2 heterostructure photodetector fabricated by photolithography exhibits an enhanced photoresponsivity up to 370 A W−1 in comparison with single WS2 or MoS2 devices. This study suggests a direct CVD growth of large-scale TMDC heterostructure films with clean interface. The built-in electric field at interface contributes to the separation of photo-generated electron–hole pairs, leading to enhanced photocurrent and responsivity, and showing promising potentials in photo-electric applications.

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Miller-Link, Elisa. "(Invited) Electrochemical Conversion of Nitrogen to Ammonia Using 2D Transition Metal Dichalcogenides." ECS Meeting Abstracts MA2022-02, no. 49 (October 9, 2022): 1926. http://dx.doi.org/10.1149/ma2022-02491926mtgabs.

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We use 2D transition metal dichalcogenide (TMDC) catalysts to facilitate the nitrogen (N2) reduction to ammonia (NH3) via dark electrocatalysis. TMDCs are an important class of materials because they can be reduced to 2D, where their quantum confined properties are easily manipulated for various applications. Transition metal-based catalysts offer a unique opportunity to exploit the d electrons and orbitals for N2 activation, where we specifically compare theoretically and experimentally MoS2, TiS2, and VS2. In addition, the 2D TMDC catalysts are highly tunable 2D catalysts, where the band energetics, surface functionalization, defects, and phase can be tuned to control the N2 reactivity. We use indophenol and 1H NMR with isotope labeling to identify and quantify NH3 from the catalytic reaction and not from setup/system contaminants; moreover, we use density functional theory to add insight into the 2D TMDC active site and reaction pathway. Through various attempts and iterations, we have many lessons learned about experimental and theoretical setup that will be communicated.

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Xie, Yong, Xiaohua Ma, Zhan Wang, Tang Nan, Ruixue Wu, Peng Zhang, Haolin Wang, Yabin Wang, Yongjie Zhan, and Yue Hao. "NaCl-Assisted CVD Synthesis, Transfer and Persistent Photoconductivity Properties of Two-Dimensional Transition Metal Dichalcogenides." MRS Advances 3, no. 6-7 (2018): 365–71. http://dx.doi.org/10.1557/adv.2018.156.

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AbstractTransition metal dichalcogenides (TMDC), such as MoS2, WS2 have attracted attention due to their mechanical and electronic properties in their two dimensional (2D) structures. Here, we report a facile growth of monolayer TMDC using oxide source materials with the assistant of NaCl. The addition of NaCl can enhance the lateral growth and widen the growth window of TMDC. Through carefully controlling the growth parameters, large area growth of TMDC can be achieved. Two steps E-beam lithography was utilized to fabricate electrodes of TMDC. The phototransistors made from the CVD grown TMDC show strong persistent photoconductivity (PPC). It was finally shown that TMDC device capping with h-BN could have suppressed PPC effects.

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DAVE, MEHUL. "Optical analysis for few TMDC materials." Bulletin of Materials Science 38, no. 7 (December 2015): 1791–96. http://dx.doi.org/10.1007/s12034-015-0960-6.

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Bassman, Lindsay, Aravind Krishnamoorthy, Aiichiro Nakano, Rajiv K. Kalia, Hiroyuki Kumazoe, Masaaki Misawa, Fuyuki Shimojo, and Priya Vashishta. "Picosecond Electronic and Structural Dynamics in Photo-excited Monolayer MoSe2." MRS Advances 3, no. 6-7 (2018): 391–96. http://dx.doi.org/10.1557/adv.2018.259.

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Monolayers of semiconducting transitional metal dichalcogenides (TMDC) are emerging as strong candidate materials for next generation electronic and optoelectronic devices, with applications in field-effect transistors, valleytronics, and photovoltaics. Prior studies have demonstrated strong light-matter interactions in these materials, suggesting optical control of material properties as a promising route for their functionalization. However, the electronic and structural dynamics in response to electronic excitation have not yet been fully elucidated. In this work, we use non-adiabatic quantum molecular dynamics simulations based on time-dependent density functional theory to study lattice dynamics of a model TMDC monolayer of MoSe2 after electronic excitation. The simulation results show rapid, sub-picosecond lattice response, as well as finite-size effects. Understanding the sub-picosecond atomic dynamics is important for the realization of optical control of the material properties of monolayer TMDCs, which is a hopeful, straightforward tactic for functionalizing these materials.

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Ahmed, Hasan, and Viktoriia E. Babicheva. "Nanostructured Tungsten Disulfide WS2 as Mie Scatterers and Nanoantennas." MRS Advances 5, no. 35-36 (2020): 1819–26. http://dx.doi.org/10.1557/adv.2020.173.

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ABSTRACTNanoparticles of high-refractive-index materials like semiconductors can achieve confinement of light at the subwavelength scale because of the excitation of Mie resonances. The nanostructures out of high-refractive-index materials have extensively been studied theoretically and realized in experiments exploring a wide range of photonic applications. Recently, transition metal dichalcogenides (TMDCs) from the family of van der Waals layered materials have been shown to exhibit tailorable optical properties along with high refractive index and strong anisotropy. We envision that TMDCs are a promising material platform for designing metasurfaces and ultra-thin optical elements: these van der Waals materials show a strong spectral response on light excitations in visible and near-infrared ranges, and metasurface properties can be controlled by nanoantenna dimensions and their arrangement. In this work, we investigate a periodic array of disk-shaped nanoantennas made of a TMDC material, tungsten disulfide WS2, placed on top of a silicon layer and oxide substrate. We show that the nanostructure resonance in TMDC disk-shaped nanoantenna array can be controlled by the variation in silicon layer thickness and have a dependence on the presence of index-match superstrate cover. We also report on the spectral features in absorption and reflection profiles of the same structure with different surrounding index.

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Lattyak, Colleen, Volker Steenhoff, Kai Gehrke, Martin Vehse, and Carsten Agert. "Two-Dimensional Absorbers for Solar Windows: A Simulation." Zeitschrift für Naturforschung A 74, no. 8 (August 27, 2019): 683–88. http://dx.doi.org/10.1515/zna-2019-0134.

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AbstractIn the future, many modern buildings may rely on solar windows for energy production. Large buildings often have glass facades that have the potential to convert sunlight to electrical power. The standard photovoltaic materials used today are bulky and not transparent, making them poor candidates for solar windows. Transition metal dichalcogenides (TMDCs) and other two-dimensional absorbers are a good alternative because of their unique properties and high transparency at the monolayer and few-layer regime. This work shows the potential for TMDC-based solar windows by simulating the transmission, quantum efficiency, current density, and colour appearance of different solar cell configurations. Different contacts were investigated, along with the influence of contact thickness, to demonstrate colour-neutral solar cells. In addition, four TMDC materials were compared: MoS2, MoSe2, WS2, and WSe2. Colour-neutral solar cells with transparencies of 35 % to 55 % are presented, where a current density of 8.33 mA/cm2 was calculated for a solar cell with a 5-nm absorbing layer of MoSe2. While there are still challenges to overcome in terms of production, our simulations show that it is possible to use TMDCs for colour-neutral solar windows and act as a guideline for further research.

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Tang, Shin-Yi, Teng-Yu Su, Tzu-Yi Yang, and Yu-Lun Chueh. "Novel Design of 0D Nanoparticles-2D Transition-Metal Dichalcogenides Heterostructured Devices for High-Performance Optical and Gas-Sensing Applications." ECS Meeting Abstracts MA2022-02, no. 36 (October 9, 2022): 1318. http://dx.doi.org/10.1149/ma2022-02361318mtgabs.

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Two-dimensional Transition metal dichalcogenides (TMDCs), have now attracted much attention due to their unique layered structure and physical properties. Up to date, several studies have demonstrated monolayered and few-layered TMDC-based photodetectors with good stability, photo-switching time and broadband detectivity from UV to infrared light region. However, the reported responsivity is not as high as the theoretical expectation, indicating that the light absorption is limited by the atomic thickness of 2D-TMDCs and could still be improved. To overcome the drawback of low absorption in 2D TMDC materials, previous reports have revealed several strategies to enhance the electric field and light-harvesting in these atomically thin TMDC layers by hybridizing plasmonic noble-metal nanoparticles, such as Pt, Au and Ag, to facilitate the light-matter interaction at the surface of semiconductors. In this regard, we aim to combine highly absorptive CuInS2(CIS) nanocrystals with noble metal nanoparticles as the photosensitizer to enhance the intrinsic absorptivity and promote the performance of MoS2-based photodetectors. The interests of noble nanocrystals such as platinum and gold are featured for their distinctive properties of the carrier transportation and the storage when combined with semiconductor materials. The strategy described here acts as a perspective to signiﬁcantly improve the performance of MoS2-based photodetectors with outstanding detection responsivity with selectable wavelengths by further controlling the size and material of the decorated CIS nanocrystals. In addition to optical sensing, TMDCs have also been developed as a promising candidate for gas-molecule detection. Different from commercial metal oxide gas sensors, TMDCs as sensing materials can be operated at room temperature with good performance, increasing its reliability for future industrial applications. Nevertheless, the relatively low response and long response/recovery time are the main drawbacks of these promising devices. Therefore, we proposed the approach to successfully increase the surface area of TMDCs by a one-step synthesis from WO3 into three-dimensional (3D) WS2 nanowalls through a rapid heating and rapid cooling process. Moreover, the combination of CdS/ZnS or CdSe/ZnS core/shell quantum dots (QDs) with different emission wavelengths and WS2 nanowalls will further improve the performance of WS2-based photodetector devices, including 3.5~4.7 times photocurrent enhancement and shorter response time. The remarkable results of the QD-WS2 hybrid devices to the high non-radiative energy transfer (NRET) efficiency between QDs and our nanostructured material are caused by the spectral overlap between the emission of QDs as the donors and the absorption of WS2 as the acceptors. Additionally, the outstanding NO2 gas-sensing properties of QDs/WS2 devices were demonstrated with a remarkably low detection limit down to 50 ppb with a fast response time of 26.8 s, contributed by tremendous local p-n junctions generated from p-type WS2 nanowalls and n-type CdSe-ZnS QDs in this hybrid system. Our strategies to combine 0D nanoparticles or quantum dots and 2D TMDC materials can significantly enhance the optical sensing and gas molecule sensing properties compared to pristine TMDC-based devices, resulting from the efficient charge or energy transfer between the multi-dimension material system and the creation of local p-n junctions. Moreover, the scalability of these hybrid nanostructures allows our devices to exhibit much more possibilities in advanced multifunctional applications.

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Babicheva, Viktoriia E. "Transition Metal Dichalcogenide Nanoantennas Lattice." MRS Advances 4, no. 41-42 (2019): 2283–88. http://dx.doi.org/10.1557/adv.2019.357.

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ABSTRACTHigh-index materials such as silicon and III-V compounds have recently gained a lot of interest as a promising material platform for efficient photonic nanostructures. Because of the high refractive index, nanoparticles of such materials support Mie resonances and enable efficient light control and its confinement at the nanoscale. Here we propose a design of nanostructure with multipole resonances where optical nanoantennas are made out of transition metal dichalcogenide, in particular, tungsten disulfide WS2. Transition metal dichalcogenide (TMDCs) possess a high refractive index and strong optical anisotropy because of their layered structure and are promising building blocks for next-generation photonic devices. Strong anisotropic response results in different components of TMDC permittivity and the possibility of tailoring nanostructure optical properties by choosing different axes and adjusting dimensions in design. The proposed periodic array of TMDC nanoantennas can be used for controlling optical resonances in the visible and near-infrared spectral ranges and engineering efficient ultra-thin optical components with nanoscale light confinement.

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Lee, Yeon, Dasol Kim, Dong-Eon Kim, and Alexis Chacón. "High Harmonic Generation in Monolayer and Bilayer of Transition Metal Dichalcogenide." Symmetry 13, no. 12 (December 12, 2021): 2403. http://dx.doi.org/10.3390/sym13122403.

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In transition metal dichalcogenides (TMDCs), charge carriers have spin, pseudospin, and valley degrees of freedom associated with magnetic moments. The monolayers and bilayers of the TMDCs, in particular, MoS2, lead to strong couplings between the spin and pseudospin effects. This feature has drawn attention to TMDCs for their potential use in advanced tech devices. Meanwhile, high-order harmonic generation (HHG) has recently been applied to the characterization of the electronic structure of solids, such as energy dispersion, Berry-curvature, and topological properties. Here, we show theoretical results obtained with the ‘philosophy’ of using HHG to investigate the structural effects of the monolayer and bilayers of MoS2 on nonlinear optical emission. We use a simple model for MoS2 in the 3R AB staking. We find that the pseudospin and valley indexes (the Berry curvature and the dipole transition matrix element) in TMDC driven by a circularly polarized laser (CPL) can encode in the high-energy photon emissions. This theoretical investigation is expected to pave the way for the ultrafast manipulation of valleytronics and lead to new questions concerning the spin-obit-coupling (SOC) effects on TMDC materials, Weyl Semimetals, and topological phases and transitions in topological insulators.

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Lunardon, Marco, JiaJia Ran, Dario Mosconi, Carla Marega, Zhanhua Wang, Hesheng Xia, Stefano Agnoli, and Gaetano Granozzi. "Hybrid Transition Metal Dichalcogenide/Graphene Microspheres for Hydrogen Evolution Reaction." Nanomaterials 10, no. 12 (November 28, 2020): 2376. http://dx.doi.org/10.3390/nano10122376.

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A peculiar 3D graphene-based architecture, i.e., partial reduced-Graphene Oxide Aerogel Microspheres (prGOAM), having a dandelion-like morphology with divergent microchannels to implement innovative electrocatalysts for the hydrogen evolution reaction (HER) is investigated in this paper. prGOAM was used as a scaffold to incorporate exfoliated transition metals dichalcogenide (TMDC) nanosheets, and the final hybrid materials have been tested for HER and photo-enhanced HER. The aim was to create a hybrid material where electronic contacts among the two pristine materials are established in a 3D architecture, which might increase the final HER activity while maintaining accessible the TMDC catalytic sites. The adopted bottom-up approach, based on combining electrospraying with freeze-casting techniques, successfully provides a route to prepare TMDC/prGOAM hybrid systems where the dandelion-like morphology is retained. Interestingly, the microspherical morphology is also maintained in the tested electrode and after the electrocatalytic experiments, as demonstrated by scanning electron microscopy images. Comparing the HER activity of the TMDC/prGOAM hybrid systems with that of TMDC/partially reduced-Graphene Oxide (prGO) and TMDC/Vulcan was evidenced in the role of the divergent microchannels present in the 3D architecture. HER photoelectron catalytic (PEC) tests have been carried out and demonstrated an interesting increase in HER performance.

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Presutti, Dario, Tarun Agarwal, Atefeh Zarepour, Nehar Celikkin, Sara Hooshmand, Chinmay Nayak, Matineh Ghomi, et al. "Transition Metal Dichalcogenides (TMDC)-Based Nanozymes for Biosensing and Therapeutic Applications." Materials 15, no. 1 (January 4, 2022): 337. http://dx.doi.org/10.3390/ma15010337.

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Nanozymes, a type of nanomaterial with enzyme-like properties, are a promising alternative to natural enzymes. In particular, transition metal dichalcogenides (TMDCs, with the general formula MX2, where M represents a transition metal and X is a chalcogen element)-based nanozymes have demonstrated exceptional potential in the healthcare and diagnostic sectors. TMDCs have different enzymatic properties due to their unique nano-architecture, high surface area, and semiconducting properties with tunable band gaps. Furthermore, the compatibility of TMDCs with various chemical or physical modification strategies provide a simple and scalable way to engineer and control their enzymatic activity. Here, we discuss recent advances made with TMDC-based nanozymes for biosensing and therapeutic applications. We also discuss their synthesis strategies, various enzymatic properties, current challenges, and the outlook for future developments in this field.

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Hasib, Mohammad Hasibul Hasan, Jannati Nabiha Nur, Conrad Rizal, and Kamrun Nahar Shushama. "Improved Transition Metal Dichalcogenides-Based Surface Plasmon Resonance Biosensors." Condensed Matter 4, no. 2 (May 22, 2019): 49. http://dx.doi.org/10.3390/condmat4020049.

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Surface plasmon resonance (SPR) biosensors based on transition metal dichalcogenides (TMDC) materials have shown improved performance in terms of sensitivity, detection accuracy (DA), and quality factor (QF) over conventional biosensors. In this paper, we propose a five-layers model containing black phosphorus (BP) and TMDC (Ag/BP/WS2) in Kretschmann configuration. Using TM-polarized light at 633 nm, we numerically demonstrate the highest sensitivity (375°/RIU), DA (0.9210), and QF (65.78 1/RIU) reported so far over similar materials. Refractive index (RI) of the coupling prism has also played an essential role in enhancing the performance of these biosensors. The research on TMDC materials is still new, and these materials bring about opportunities to develop a new class of biosensor.

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Wang, Siyuan, Guang Wang, Xi Yang, Hang Yang, Mengjian Zhu, Sen Zhang, Gang Peng, and Zheng Li. "Synthesis of Monolayer MoSe2 with Controlled Nucleation via Reverse-Flow Chemical Vapor Deposition." Nanomaterials 10, no. 1 (December 31, 2019): 75. http://dx.doi.org/10.3390/nano10010075.

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Two-dimensional (2D) layered semiconductor materials, such as transition metal dichalcogenides (TMDCs), have attracted considerable interests because of their intriguing optical and electronic properties. Controlled growth of TMDC crystals with large grain size and atomically smooth surface is indeed desirable but remains challenging due to excessive nucleation. Here, we have synthesized high-quality monolayer, bilayer MoSe2 triangular crystals, and continuous thin films with controlled nucleation density via reverse-flow chemical vapor deposition (CVD). High crystallinity and good saturated absorption performance of MoSe2 have been systematically investigated and carefully demonstrated. Optimized nucleation and uniform morphology could be achieved via fine-tuning reverse-flow switching time, growth time and temperature, with corresponding growth kinetics proposed. Our work opens up a new approach for controllable synthesis of monolayer TMDC crystals with high yield and reliability, which promote surface/interface engineering of 2D semiconductors towards van der Waals heterostructure device applications.

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Zhang, Qi, Fengjiao Xu, Pei Lu, Di Zhu, Lihui Yuwen, and Lianhui Wang. "Efficient Preparation of Small-Sized Transition Metal Dichalcogenide Nanosheets by Polymer-Assisted Ball Milling." Molecules 27, no. 22 (November 12, 2022): 7810. http://dx.doi.org/10.3390/molecules27227810.

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Two-dimensional (2D) transition metal dichalcogenide nanosheets (TMDC NSs) have attracted growing interest due to their unique structure and properties. Although various methods have been developed to prepare TMDC NSs, there is still a great need for a novel strategy combining simplicity, generality, and high efficiency. In this study, we developed a novel polymer-assisted ball milling method for the efficient preparation of TMDC NSs with small sizes. The use of polymers can enhance the interaction of milling balls and TMDC materials, facilitate the exfoliation process, and prevent the exfoliated nanosheets from aggregating. The WSe2 NSs prepared by carboxymethyl cellulose sodium (CMC)-assisted ball milling have small lateral sizes (8~40 nm) with a high yield (~60%). The influence of the experimental conditions (polymer, milling time, and rotation speed) on the size and yield of the nanosheets was studied. Moreover, the present approach is also effective in producing other TMDC NSs, such as MoS2, WS2, and MoSe2. This study demonstrates that polymer-assisted ball milling is a simple, general, and effective method for the preparation of small-sized TMDC NSs.

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Chen, Haitao, Mingkai Liu, Lei Xu, and Dragomir N. Neshev. "Valley-selective directional emission from a transition-metal dichalcogenide monolayer mediated by a plasmonic nanoantenna." Beilstein Journal of Nanotechnology 9 (March 2, 2018): 780–88. http://dx.doi.org/10.3762/bjnano.9.71.

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Background: Two-dimensional (2D) transition-metal dichalcogenides (TMDCs) with intrinsically crystal inversion-symmetry breaking have shown many advanced optical properties. In particular, the valley polarization in 2D TMDCs that can be addressed optically has inspired new physical phenomena and great potential applications in valleytronics. Results: Here, we propose a TMDC–nanoantenna system that could effectively enhance and direct emission from the two valleys in TMDCs into diametrically opposite directions. By mimicking the emission from each valley of the monolayer of WSe2 as a chiral point-dipole emitter, we demonstrate numerically that the emission from different valleys is directed into opposite directions when coupling to a double-bar plasmonic nanoantenna. The directionality derives from the interference between the dipole and quadrupole modes excited in the two bars, respectively. Thus, we could tune the emission direction from the proposed TMDC–nanoantenna system by tuning the pumping without changing the antenna structure. Furthermore, we discuss the general principles and the opportunities to improve the average performance of the nanoantenna structure. Conclusion: The scheme we propose here can potentially serve as an important component for valley-based applications, such as non-volatile information storage and processing.

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Nan, Haiyan, Renwu Zhou, Xiaofeng Gu, Shaoqing Xiao, and Kostya (Ken) Ostrikov. "Recent advances in plasma modification of 2D transition metal dichalcogenides." Nanoscale 11, no. 41 (2019): 19202–13. http://dx.doi.org/10.1039/c9nr05522c.

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Niu, Yue, Sergio Gonzalez-Abad, Riccardo Frisenda, Philipp Marauhn, Matthias Drüppel, Patricia Gant, Robert Schmidt, et al. "Thickness-Dependent Differential Reflectance Spectra of Monolayer and Few-Layer MoS2, MoSe2, WS2 and WSe2." Nanomaterials 8, no. 9 (September 14, 2018): 725. http://dx.doi.org/10.3390/nano8090725.

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The research field of two dimensional (2D) materials strongly relies on optical microscopy characterization tools to identify atomically thin materials and to determine their number of layers. Moreover, optical microscopy-based techniques opened the door to study the optical properties of these nanomaterials. We presented a comprehensive study of the differential reflectance spectra of 2D semiconducting transition metal dichalcogenides (TMDCs), MoS2, MoSe2, WS2, and WSe2, with thickness ranging from one layer up to six layers. We analyzed the thickness-dependent energy of the different excitonic features, indicating the change in the band structure of the different TMDC materials with the number of layers. Our work provided a route to employ differential reflectance spectroscopy for determining the number of layers of MoS2, MoSe2, WS2, and WSe2.

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Krasnok, Alexander, and Andrea Alù. "Valley-Selective Response of Nanostructures Coupled to 2D Transition-Metal Dichalcogenides." Applied Sciences 8, no. 7 (July 17, 2018): 1157. http://dx.doi.org/10.3390/app8071157.

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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.

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Zhumagulov, Yaroslav V., Alexei Vagov, Dmitry R. Gulevich, and Vasili Perebeinos. "Electrostatic and Environmental Control of the Trion Fine Structure in Transition Metal Dichalcogenide Monolayers." Nanomaterials 12, no. 21 (October 24, 2022): 3728. http://dx.doi.org/10.3390/nano12213728.

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Charged excitons or trions are essential for optical spectra in low-dimensional doped monolayers (ML) of transitional metal dichalcogenides (TMDC). Using a direct diagonalization of the three-body Hamiltonian, we calculate the low-lying trion states in four types of TMDC MLs as a function of doping and dielectric environment. We show that the fine structure of the trion is the result of the interplay between the spin-valley fine structure of the single-particle bands and the exchange interaction. We demonstrate that by variations of the doping and dielectric environment, the fine structure of the trion energy can be tuned, leading to anticrossing of the bright and dark states, with substantial implications for the optical spectra of the TMDC ML.

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Morin, Pierre, Benjamin Groven, Henry Medina, Yuanyuan Shi, Vladislav Voronenkov, Iryna Kandybka, Annelies Delabie, et al. "(Invited) Addressing Key Process and Material Challenges to Enable 2D Transition Metal Dichalcogenide Channels in Advanced Logic Devices." ECS Meeting Abstracts MA2022-02, no. 15 (October 9, 2022): 822. http://dx.doi.org/10.1149/ma2022-0215822mtgabs.

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Two dimensional ultrathin layers are considered promising materials to bring new functionalities in nanotechnologies and candidate to replace 3D materials in existing applications. Among this last category, transition metal dichalcogenides (TMDC) like WS2, MoS2, WSe2 are viewed as interesting alternative channels for ultra-scaled CMOS technologies, as silicon is approaching its physical limits. These semiconductor 2D monolayers could bring a decisive advantage in terms of electrostatic control at very low gate length, while maintaining decent carrier transport properties as compared to 3D materials at same dimension. In addition, TMDC should provide improved off current performance as compared to silicon, an important factor to improve the static power efficiency in multibillion transistor chips. Obviously, replacing the channel material of the main device in microelectronics, from silicon to TMDC, comes with a very long list of scientific and technological challenges to be addressed. In this paper we limit our scope to the growth of TMDC, one of the main pillar in this global effort, and share how we addressed some of the challenges related to the formation of 2D semiconductor channels, to enable the fabrication of functioning devices on lab and 300 mm flows. TMDCs thin films grown with metal oxide CVD on substrates with, in some case, the presence of NaCl salts, are demonstrating the largest grain size and the best electrical performance but these processes are hardly compatible with industrial CVD reactors. In contrast we use chemistries more compatible with manufacturing, with the target of growing TMDC on 300 mm substrates. We report on MoS2 and WS2 formed with chemistries using metal organic precursors such as Mo(CO)6 or W(CO)6 and di-hydrogen sulfide grown in customized epitaxial cross flow 200 and 300 mm reactors [1]. We report basic nucleation and growth studies over a large process domain which show the possibility to control the density of nuclei and the subsequent lateral crystal growth while minimizing secondary nucleation and metal particle defectivity. We study the deposition of MoS2 an WS2 on two basic types of substrates defining fundamentally the integration schemes. On one route, dedicated to device performance demonstration, TMDC monolayers are grown on templated substrates like sapphire following a van der Waals epitaxy mode which enables regular orientation of the crystallites and formation of large and oriented domains after grain ripening with reduced defect concentration. The 2D layer is then transferred onto the final substrate for the device formation. With this technique, average mobilities above 30 cm2/Vs have been achieved regularly on MoS2 backgated devices, and the best devices exhibit currents at transfer curve up to 420 mA/mm [2,3]. On the other flow, recent efforts have aimed at growing WS2 directly on various types of amorphous substrate layer typically deposited on 300mm wafer, acting either as bottom gate dielectric or sacrificial layer. This scheme doesn’t require subsequent transfer step. However, after integration, these materials demonstrate performance still substantially lower than with material grown on sapphire [4,5]. As the device dimensions has scaled down over the last 20 years, improving the variability at different scales has emerged as major topic in microelectronics. TMDC channels are no exception to this trend despite intrinsic advantage in terms of thickness control. We will share on specific work done on sapphire surface specification and preparation. We have demonstrated that depositing MoS2 on 1° off-A axis C-plane sapphire substrate reduced the dispersion in mobility as compared to similar materials obtained on C-plane oriented on-axis substrates [6]. We have also worked-out in-situ Cl2 etch process to remove the superficial islands grown on top of the first layer MoS2 crystals as this first layer is being closed. The process enables full lateral etching of the secondary layer crystals selectively to the closed first layer. With this process, we observed substantial improvement in the electrostatic control of MoS2 scaled transistors, including threshold voltage variability and improved subthreshold swing control [7]. We continue to work out the TMDC growth process to improve the material quality, impacted by the presence of defects at the grain boundaries or intra-grain, aiming to close the gap with advanced logic requirements. 1-Caymax & al., SSDM, D-1-03, 2019 2-D Lin & al., Symposium on VLSI Technology, 1-2, 2021 3- Wu & al., IEDM, 7.4.1-7.4.4, 2021 4- Asselberghs & al., IEDM, 40.2.1- 40.2.4, 2020 5- Smets & al., IEDM, 34.2.1-34.2.4, 2021 6- Shi & al., ACS nano 15 (6), 9482-9494, 2021 7- Shi & al., IEDM, 37.1.1-37.1.4, 2021

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Zafar, Muhammad Shahzad, Ghulam Dastgeer, Abul Kalam, Abdullah G. Al-Sehemi, Muhammad Imran, Yong Ho Kim, and Heeyeop Chae. "Precise and Prompt Analyte Detection via Ordered Orientation of Receptor in WSe2-Based Field Effect Transistor." Nanomaterials 12, no. 8 (April 11, 2022): 1305. http://dx.doi.org/10.3390/nano12081305.

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Field-effect transistors (FET) composed of transition metal dichalcogenide (TMDC) materials have gained huge importance as biosensors due to their added advantage of high sensitivity and moderate bandgap. However, the true potential of these biosensors highly depends upon the quality of TMDC material, as well as the orientation of receptors on their surfaces. The uncontrolled orientation of receptors and screening issues due to crossing the Debye screening length while functionalizing TMDC materials is a big challenge in this field. To address these issues, we introduce a combination of high-quality monolayer WSe2 with our designed Pyrene-based receptor moiety for its ordered orientation onto the WSe2 FET biosensor. A monolayer WSe2 sheet is utilized to fabricate an ideal FET for biosensing applications, which is characterized via Raman spectroscopy, atomic force microscopy, and electrical prob station. Our construct can sensitively detect our target protein (streptavidin) with 1 pM limit of detection within a short span of 2 min, through a one-step functionalizing process. In addition to having this ultra-fast response and high sensitivity, our biosensor can be a reliable platform for point-of-care-based diagnosis.

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Taniguchi, Takaaki, Leanddas Nurdiwijayanto, Renzhi Ma, and Takayoshi Sasaki. "Chemically exfoliated inorganic nanosheets for nanoelectronics." Applied Physics Reviews 9, no. 2 (June 2022): 021313. http://dx.doi.org/10.1063/5.0083109.

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Two-dimensional (2D) nanomaterials constitute one of the most advanced research targets in materials science and engineering in this century. Among various methods for the synthesis of 2D nanomaterials, including top-down exfoliation and bottom-up crystal growth, chemical exfoliation has been widely used to yield monolayers of various layered compounds, such as clay minerals, transition metal chalcogenides (TMDCs), and oxides, long before the discovery of graphene. Soft chemical exfoliation is a technique to weaken the layer-to-layer interaction in layered compounds by chemical modification of interlayer galleries, which promotes monolayer exfoliation. The chemical exfoliation process using organic substances, typically amines, has been applied to a range of layered metal oxides and hydroxides for two decades, establishing high-yield exfoliation into their highly crystalline monolayers and colloidal integration processes have been developed to assemble the resultant 2D nanomaterials into well-organized nanoscale devices. Recently, such a strategy was found to be effective for TMDC and MXene nanosheets, expanding the lineup of functionalities of solution-processed 2D nanomaterial devices from dielectrics, optics, magnetics, and semiconductors to superconductors. Throughout this review, we share the historical research flow, recent progress, and prospects in the development of soft-chemical exfoliation, colloidal integration, and thin film applications of oxides, TMDC, and MXene nanosheets.

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Wunderlich, Bernhard. "Quasi-isothermal temperature-modulated differential scanning calorimetry (TMDSC) for the separation of reversible and irreversible thermodynamic changes in glass transition and melting ranges of flexible macromolecules." Pure and Applied Chemistry 81, no. 10 (October 3, 2009): 1931–52. http://dx.doi.org/10.1351/pac-con-08-07-05.

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With standard differential scanning calorimetry (DSC), it is possible to derive calorimetric data for equilibrium or metastable samples. The introduction of temperature-modulated DSC (TMDSC) permits in its quasi-isothermal (non-scanning) mode (TMDC), long-time apparent heat capacity measurements of high precision (±1 %). For flexible molecules, heat capacity measurements from the various calorimetric methods could be combined in the ATHAS Data Bank, which now contains experimental data for over 200 materials. These data were linked to the vibrational and large-amplitude motion of the constituent atoms and molecules, to provide a base for the judgement of the thermal analyses, extending outside the range of equilibrium or metastability with an error of only 2-5 %. The TMDC together with DSC is now able to quantitatively assess the reversibility of thermal processes. A sufficient number of systems have been analyzed in this fashion to develop better understanding of macro-, micro-, and nanophases of flexible macromolecules. The new concepts discussed are: (1) multiple glass transitions due to possible rigid-amorphous fractions (RAFs) and glass transitions within crystals, both observed in semicrystalline macromolecules, and (2) locally reversibly melting on the surface of chain-folded crystals. The locally reversible melting decreases with crystal perfection and also disappears when the chains become rigid.

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Chen, Fei, Xia Jiang, Xin Zheng, Bin Lu, and Tingting Deng. "Fabrication and Optical Performance of Mo1-xWxS2 Monolayer with Different Composition Ranges via One-Step Chemical Vapor Deposition Approach." Journal of Nanoelectronics and Optoelectronics 15, no. 12 (December 1, 2020): 1544–51. http://dx.doi.org/10.1166/jno.2020.2886.

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Fabrication of 2D TMDCs with variable bandgap can supply a prospective platform for the multi-functional applications in optoelectronics. Here, we present a one-step CVD strategy for realization of 2D Mo1-xWxS2 flakes with different x ranges through adjusting growth temperature. Detailed Raman and photoluminescence spectra/mappings have elucidated that as-produced Mo1-xWxS2 alloys exhibit significant compositiondependent structural and optical modulation. The variation of Mo1-xWxS2 alloy with diverse composition ranges has discussed based on the effect of growth temperature on the evaporation and interdiffusion of Mo/W atoms. The present results will provide a favorable guidance for the controllable fabrication of other 2D TMDC alloys, providing prospective materials for functional optoelectronics.

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Kim, Hyunseung, Changwan Sohn, Seongbin Im, and Chang Kyu Jeong. "Triboelectric Pressure Sensors Using Laser-Directed Synthesis of Strain-Induced Crumpled MoS2." ECS Meeting Abstracts MA2022-02, no. 62 (October 9, 2022): 2293. http://dx.doi.org/10.1149/ma2022-02622293mtgabs.

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Two-dimensional (2D) transition metal dichalcogenide (TMDC) nanomaterials are currently regarded as next generation electronic materials for future flexible, transparent, and wearable electronics. Due to the lack of compatible synthesis and study, however, the characteristic influences of 2D TMDC nanomaterials have been little investigated in the field of triboelectric nanogenerator (TENG) devices that are currently one of the main technologies for mechanical energy harvesting. In this report, we demonstrate a fast, non-vacuum, wafer-scale, and patternable synthesis method for 2D MoS2 using pulsed laser-directed thermolysis. The laser-based synthesis technique that we have developed can apply internal stress to MoS2 crystal by adjusting its morphological structure, so that a surface-crumpled MoS2 TENG device generates ~40% more power than a flat MoS2 one. Compared to other MoS2-based TENG devices, it shows high-performance energy harvesting (up to ~25 V and ~1.2 μA) without assistance from other materials, even when the counterpart triboelectric surface has a slightly different triboelectric series. This enhanced triboelectrification is attribute to work function change as well as enlarged surface roughness. Finally, the direct-synthesized MoS2 patterns are utilized to fabricate a self-powered flexible haptic sensor array. The technique we propose here is intended to stimulate further investigation of the triboelectric effects and applications of 2D TMDC nanomaterials.

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López-Posadas, Claudia Beatriz, Yaxu Wei, Wanfu Shen, Daniel Kahr, Michael Hohage, and Lidong Sun. "Direct observation of the CVD growth of monolayer MoS2 using in situ optical spectroscopy." Beilstein Journal of Nanotechnology 10 (February 26, 2019): 557–64. http://dx.doi.org/10.3762/bjnano.10.57.

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Real-time monitoring is essential for understanding and precisely controlling of growth of two-dimensional transition metal dichalcogenide (2D TMDC) materials. However, it is very challenging to carry out such studies during chemical vapor deposition (CVD). Here, we report the first, real time, in situ study of the CVD growth of 2D TMDCs. More specifically, the CVD growth of a molybdenum disulfide (MoS2) monolayer on sapphire substrates has been monitored in situ using differential transmittance spectroscopy (DTS). The growth of the MoS2 monolayer can be precisely followed by observation of the evolution of the characteristic optical features. Consequently, a strong correlation between the growth rate of the MoS2 monolayer and the temperature distribution in the CVD reactor has been revealed. Our results demonstrate the great potential of real time, in situ optical spectroscopy to assist the precisely controlled growth of 2D semiconductor materials.

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Hong, Sungwook, Aravind Krishnamoorthy, Chunyang Sheng, Rajiv K. Kalia, Aiichiro Nakano, and Priya Vashishta. "A Reactive Molecular Dynamics Study of Atomistic Mechanisms During Synthesis of MoS2 Layers by Chemical Vapor Deposition." MRS Advances 3, no. 6-7 (2018): 307–11. http://dx.doi.org/10.1557/adv.2018.67.

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ABSTRACTTransition metal dichalcogenide (TMDC) monolayers like MoS2 are promising materials for future electronic applications. Large-area monolayer MoS2 samples for these applications are typically synthesized by chemical vapor deposition (CVD) using MoO3 reactants and gas-phase sulfur precursors. Recent experimental studies have greatly improved our understanding of reaction pathways in the CVD growth process. However, atomic mechanisms of sulfidation process remain to be fully elucidated. In this work, we present quantum-mechanically informed and validated reactive molecular dynamics (RMD) simulations for CVD synthesis of MoS2 layers using S2 precursors. Our RMD simulations clarify atomic-level reaction pathways for the sulfidation of MoO3 surfaces by S2, which is a critical reaction step for CVD synthesis of MoS2 layers. These results provide a better understanding of the sulfidation process for the scalable synthesis of defect-free MoS2 and other TMDC materials.

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Kwak, Junghyeok, Sunshin Jung, Noho Lee, Kaliannan Thiyagarajan, Jong Kyu Kim, Anupam Giri, and Unyong Jeong. "Microwave-assisted synthesis of group 5 transition metal dichalcogenide thin films." Journal of Materials Chemistry C 6, no. 42 (2018): 11303–11. http://dx.doi.org/10.1039/c8tc03909g.

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Jiang, Xia, Fei Chen, Shichao Zhao, and Weitao Su. "Recent progress in the CVD growth of 2D vertical heterostructures based on transition-metal dichalcogenides." CrystEngComm 23, no. 47 (2021): 8239–54. http://dx.doi.org/10.1039/d1ce01289d.

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Cao, Zhen, Moussab Harb, Sergey M. Kozlov, and Luigi Cavallo. "Structural and Electronic Effects at the Interface between Transition Metal Dichalcogenide Monolayers (MoS2, WSe2, and Their Lateral Heterojunctions) and Liquid Water." International Journal of Molecular Sciences 23, no. 19 (October 7, 2022): 11926. http://dx.doi.org/10.3390/ijms231911926.

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Transition metal dichalcogenides (TMDCs) can be used as optical energy conversion materials to catalyze the water splitting reaction. A good catalytical performance requires: (i) well-matched semiconductor bandgaps and water redox potential for fluent energy transfer; and (ii) optimal orientation of the water molecules at the interface for kinetically fast chemical reactions. Interactions at the solid–liquid interface can have an important impact on these two factors; most theoretical studies have employed semiconductor-in-vacuum models. In this work, we explored the interface formed by liquid water and different types of TMDCs monolayers (MoS2, WSe2, and their lateral heterojunctions), using a combined molecular dynamics (MD) and density functional theory (DFT) approach. The strong interactions between water and these semiconductors confined the adsorbed water layer presenting structural patterns, with the water molecules well connected to the bulk water through the hydrogen bonding network. Structural fluctuations in the metal chalcogenide bonds during the MD simulations resulted in a 0.2 eV reduction of the band gap of the TMDCs. The results suggest that when designing new TMDC semiconductors, both the surface hydrophobicity and the variation of the bandgaps originating from the water-semiconductor interface, need to be considered.

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Bignardi, Luca, Sanjoy K. Mahatha, Daniel Lizzit, Harsh Bana, Elisabetta Travaglia, Paolo Lacovig, Charlotte Sanders, Alessandro Baraldi, Philip Hofmann, and Silvano Lizzit. "Anisotropic strain in epitaxial single-layer molybdenum disulfide on Ag(110)." Nanoscale 13, no. 44 (2021): 18789–98. http://dx.doi.org/10.1039/d1nr05584d.

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Uniaxial lattice strain is introduced in the lattice of a MoS2 single layer epitaxially-grown on Ag(110). Growth on a substrate with different crystalline symmetry is thus a promising way to introduce uniform strain in TMDC single layers.

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McDonnell, Stephen J., and Robert M. Wallace. "Atomically-thin layered films for device applications based upon 2D TMDC materials." Thin Solid Films 616 (October 2016): 482–501. http://dx.doi.org/10.1016/j.tsf.2016.08.068.

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Imam, Safayat Al, Khandakar Mohammad Ishtiak, and Quazi Deen Mohd Khosru. "(Invited) Broadband and Broad Angle Enhanced Light Absorption in MoS₂based Hetero Plasmonic Structure." ECS Meeting Abstracts MA2022-02, no. 36 (October 9, 2022): 1342. http://dx.doi.org/10.1149/ma2022-02361342mtgabs.

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Solar cells, photovoltaic devices and optoelectronic elements needs enhanced light absorption with a wide range of incident angle for better and efficient design. Two-dimensional (2D) materials have exceled in all areas including electrical applications, optical modulations, mechanical as well as chemical implementations due to their direct bandgap and high optical absorption nature[1]. Photon irradiation allows to generate electron-hole pairs in a direct bandgap material such as TMDCs which makes them potential candidates for large amount of light to be trapped. Different structures have been studied to achieve high optical absorption [2][3]. Although one dimensional photonic crystal(1DPC) and defective PC has good optical absorption with wide range and angle [4],[2] number of layers and complexity in structure has made it difficult to be fabricated. MoS2 monolayer structure based on cover spacer, plasmonic and dual substrate layer (SiO2(50nm)/Si ) has also increased optical absorption range and broad angle [5] but TMDC based heterostructures with spacer has improved absorption comparing to previous structures without metallic layer [6]. In this paper, we proposed a dual TMDC-spacer based plasmonic structure with dual substrate for wide and broad range and angle of near perfect optical absorption. The structure considered here is an air/MoS2/Spacer1/MoS2/Spacer2/plasmonic/dual substrate with 0.665nm, 70nm and 50nm layer of MoS2, Au as plasmonic layer and SiO2 as part of dual layer with Si as lossless substate. (Figure 1) For spacers SiO2 and TiO2 are taken with optimized value (figure 2) of 92 and 68nm for enhanced absorption. The transfer matrix of the constituted layer for either transverse electric (TE) or transverse magnetic (TM) polarization was determined using the transfer matrix method (TMM). Both in TE and TM mode, the ~30 and ~40% of enhanced light absorption are observed in proposed structure compared to hetero and mono layer structure (figure 3) with impact of metallic and spacer layer. In case of incident angle, both at resonance frequency of MoS2 and within visible range, broad angle range (00-400 for TE and 00-800 for TM) is observed with wider wavelength. (Figure 4 and figure 5). Impact of various metallic layer on the proposed structure is also observed (Figure 6). Structure with VO2 as plasmonic layer [7] has around ~95% of peak absorption (400nm-550nm) and wide incident angle (00-850) irrespective of polarizations with lieu of spacer hetero-TMDC-stack (Figure 7). Due to multiple layers of structures, collective surface plasmon polaritons (SPP) has an enhanced light absorption within the heterostructure and enhanced electric field distribution of the structure is observed (Figure 8). Table I lists some comparison among various structures and parameters indicates that proposed dual spacer -TMDC based plasmonic heterostructure has wide visible range of wavelength (400-550 nm) with broad angle (00-850) light absorption with both polarizations compare to other counterparts. In this work an enhanced range in both wavelength and incident angle of visible optical absorption is observed in both polarization with plasmonic dual heterostructure is observed and compared with other structures. Such structures are useful for photodetectors and solar cells for maximum absorptions. [1] Lopez-Sanchez O, Lembke D, Kayci M, Radenovic A and Kis A 2013 Ultrasensitive photodetectors based on monolayer MoS 2 Nat. Nanotechnol. 8 497–501 [2] Ansari N and Mohebbi E 2018 Broadband and high absorption in Fibonacci photonic crystal including MoS2 monolayer in the visible range J. Phys. D. Appl. Phys. 51 149–52 [3] Ansari N and Ghorbani F 2018 Light absorption optimization in two-dimensional transition metal dichalcogenide van der Waals heterostructures J. Opt. Soc. Am. B 35 1179 [4] Ansari N and Mohebbi E 2016 Increasing optical absorption in one-dimensional photonic crystals including MoS2 monolayer for photovoltaics applications Opt. Mater. (Amst). 62 152–8 [5] Ansari N, Mohebbi E and Gholami F 2020 Nearly perfect and broadband optical absorption by TMDCs in cover/TMDC/spacer/Au/substrate multilayers Appl. Phys. B Lasers Opt. 126 1–6 [6] Ansari N, Goudarzi B and Mohebbi E 2021 Design of narrowband or broadband absorber by heterostructures including TMDCs and spacers Opt. Laser Technol. 138 106771 [7] Das H R and Arya S C 2021 Performance improvement of VO2 and ITO based plasmonic electro-absorption modulators at 1550 nm application wavelength Opt. Commun. 479 Figure 1

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Bassman, Lindsay, Pankaj Rajak, Rajiv K. Kalia, Aiichiro Nakano, Fei Sha, Muratahan Aykol, Patrick Huck, et al. "Efficient Discovery of Optimal N-Layered TMDC Hetero-Structures." MRS Advances 3, no. 6-7 (2018): 397–402. http://dx.doi.org/10.1557/adv.2018.260.

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ABSTRACTVertical hetero-structures made from stacked monolayers of transition metal dichalcogenides (TMDC) are promising candidates for next-generation optoelectronic and thermoelectric devices. Identification of optimal layered materials for these applications requires the calculation of several physical properties, including electronic band structure and thermal transport coefficients. However, exhaustive screening of the material structure space using ab initio calculations is currently outside the bounds of existing computational resources. Furthermore, the functional form of how the physical properties relate to the structure is unknown, making gradient-based optimization unsuitable. Here, we present a model based on the Bayesian optimization technique to optimize layered TMDC hetero-structures, performing a minimal number of structure calculations. We use the electronic band gap and thermoelectric figure of merit as representative physical properties for optimization. The electronic band structure calculations were performed within the Materials Project framework, while thermoelectric properties were computed with BoltzTraP. With high probability, the Bayesian optimization process is able to discover the optimal hetero-structure after evaluation of only ∼20% of all possible 3-layered structures. In addition, we have used a Gaussian regression model to predict not only the band gap but also the valence band maximum and conduction band minimum energies as a function of the momentum.

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David, Alessandro, Guido Burkard, and Andor Kormányos. "Effective theory of monolayer TMDC double quantum dots." 2D Materials 5, no. 3 (June 8, 2018): 035031. http://dx.doi.org/10.1088/2053-1583/aac17f.

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Sigger, Florian, Hendrik Lambers, Katharina Nisi, Julian Klein, Nihit Saigal, Alexander W. Holleitner, and Ursula Wurstbauer. "Spectroscopic imaging ellipsometry of two-dimensional TMDC heterostructures." Applied Physics Letters 121, no. 7 (August 15, 2022): 071102. http://dx.doi.org/10.1063/5.0109189.

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Semiconducting two-dimensional materials and their heterostructures gained a lot of interest for applications as well as fundamental studies due to their rich optical properties. Assembly in van der Waals heterostacks can significantly alter the intrinsic optical properties as well as the wavelength-dependent absorption and emission efficiencies, making a direct comparison of, e.g., photoluminescence intensities difficult. Here, we determine the dielectric function for the prototypical MoSe2/WSe2 heterobilayer and their individual layers. Apart from a redshift of 18–44 meV of the energetically lowest interband transitions, we find that for larger energies, the dielectric function can only be described by treating the van der Waals heterobilayer as a new artificial homobilayer crystal rather than a stack of individual layers. The determined dielectric functions are applied to calculate the Michelson contrast of the individual layers and the bilayer in dependence of the oxide thickness of often used Si/SiO2 substrates. Our results highlight the need to consider the altered dielectric functions impacting the Michelson interference in the interpretation of intensities in optical measurements such as Raman scattering or photoluminescence.

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Leonhardt, Alessandra, Daniele Chiappe, Valeri V. Afanas’ev, Salim El Kazzi, Ilya Shlyakhov, Thierry Conard, Alexis Franquet, Cedric Huyghebaert, and Stefan de Gendt. "Material-Selective Doping of 2D TMDC through AlxOy Encapsulation." ACS Applied Materials & Interfaces 11, no. 45 (October 18, 2019): 42697–707. http://dx.doi.org/10.1021/acsami.9b11550.

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Zhou, Ruxin, Shuang Zhu, Linji Gong, Yanyan Fu, Zhanjun Gu, and Yuliang Zhao. "Recent advances of stimuli-responsive systems based on transition metal dichalcogenides for smart cancer therapy." Journal of Materials Chemistry B 7, no. 16 (2019): 2588–607. http://dx.doi.org/10.1039/c8tb03240h.

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A comprehensive overview of the development of stimuli-responsive TMDC-based nanoplatforms for “smart” cancer therapy is presented to demonstrate a more intelligent and better controllable therapeutic strategy.

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Zhao, Zeyu, Jie You, Jun Zhang, and Yuhua Tang. "Data-Enhanced Deep Greedy Optimization Algorithm for the On-Demand Inverse Design of TMDC-Cavity Heterojunctions." Nanomaterials 12, no. 17 (August 28, 2022): 2976. http://dx.doi.org/10.3390/nano12172976.

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A data-enhanced deep greedy optimization (DEDGO) algorithm is proposed to achieve the efficient and on-demand inverse design of multiple transition metal dichalcogenides (TMDC)-photonic cavity-integrated heterojunctions operating in the strong coupling regime. Precisely, five types of photonic cavities with different geometrical parameters are employed to alter the optical properties of monolayer TMDC, aiming at discovering new and intriguing physics associated with the strong coupling effect. Notably, the traditional rigorous coupled wave analysis (RCWA) approach is utilized to generate a relatively small training dataset for the DEDGO algorithm. Importantly, one remarkable feature of DEDGO is the integration the decision theory of reinforcement learning, which remedies the deficiencies of previous research that focused more on modeling over decision making, increasing the success rate of inverse prediction. Specifically, an iterative optimization strategy, namely, deep greedy optimization, is implemented to improve the performance. In addition, a data enhancement method is also employed in DEDGO to address the dependence on a large amount of training data. The accuracy and effectiveness of the DEDGO algorithm are confirmed to be much higher than those of the random forest algorithm and deep neural network, making possible the replacement of the time-consuming conventional scanning optimization method with the DEDGO algorithm. This research thoroughly describes the universality, interpretability, and excellent performance of the DEDGO algorithm in exploring the underlying physics of TMDC-cavity heterojunctions, laying the foundations for the on-demand inverse design of low-dimensional material-based nano-devices.

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Sujatha, R. Annie, and Betty Lincoln. "Salvaging waste heat with TMDC nanostructured materials in a thermoelectric outlook - mini review." International Journal of Nanoparticles 13, no. 4 (2021): 245. http://dx.doi.org/10.1504/ijnp.2021.10044498.

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Lincoln, Betty, and R. Annie Sujatha. "Salvaging waste heat with TMDC nanostructured materials in a thermoelectric outlook - mini review." International Journal of Nanoparticles 13, no. 4 (2021): 245. http://dx.doi.org/10.1504/ijnp.2021.120585.

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Ebadzadeh, S. F., H. Goudarzi, and M. Khezerlou. "Tunable superconducting effective gap in graphene-TMDC heterostructures." Physica B: Condensed Matter 559 (April 2019): 32–37. http://dx.doi.org/10.1016/j.physb.2019.01.041.

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Wan, Xi, Mingliang Gao, Shijia Xu, Tianhao Huang, Yaoyu Duan, EnZi Chen, Kun Chen, Xiaoliang Zeng, Weiguang Xie, and Xiaofeng Gu. "Inkjet-printed TMDC–graphene heterostructures for flexible and broadband photodetectors." Journal of Applied Physics 131, no. 23 (June 21, 2022): 234303. http://dx.doi.org/10.1063/5.0093882.

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The development of inkjet-printed 2D crystal inks offers the ability to print different 2D materials on various substrates to form vertical heterostructures. However, the detailed characterization of the atomic structures of the inkjet-printed MoTe2 nanosheets has been rarely reported. In this work, water-based 2D crystal inks of MoTe2, WS2, and graphene have been prepared and printed to obtain the flexible photodetectors. The absorption coefficient of MoTe2 has been estimated as α (500 nm) = 925 ± 47 lg−1 m−1 using the gravimetric method. Intriguingly, the inkjet-printed MoTe2 nanosheets down to 4 nm show both the semiconducting 2H and metallic 1T′ phases. The responsivities of the photodetectors based on MoTe2/graphene and WS2/graphene heterostructures can reach 120 mA/W and 2.5 A/W at 532 nm, respectively. Moreover, the inkjet-printed MoTe2/graphene shows a responsivity of 7.7 mA/W at 940 nm. The fabrication technique of inkjet printing will help design flexible optoelectronic devices based transition metal dichalcogenide–graphene heterostructures for the near-infrared photo detection.

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Lopinski, Gregory. "(Invited) Metrology of Solution Processable 2D Materials for Electronic Applications." ECS Meeting Abstracts MA2022-01, no. 18 (July 7, 2022): 1027. http://dx.doi.org/10.1149/ma2022-01181027mtgabs.

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Two-dimensional materials have attracted intense interest due to their remarkable physical and electronic properties as well as their potential for a diverse range of applications. Many of these envisaged applications (i.e. printed/flexible electronics, energy storage, photovoltaics) require single or few layer flakes of a 2D material that can be dispersed in solution to facilitate deposition onto a substrate, formulation into an ink and/or mixing into a composite. A variety of powders and dispersions claiming to contain 2D materials such as graphene are now becoming available but the variable quality of these materials and lack of standardized protocols for their assessment is hampering the development of applications. Here we will describe ongoing work at the NRC aimed at developing characterization methods and standard protocols to characterize graphene and graphene oxide (GO) powders, dispersions and inks. We employ a variety of experimental techniques including scanned probe microscopies (AFM and STM), vibrational spectroscopy (Raman and FTIR), X-ray diffraction, X-ray photoelectron spectroscopy and dynamic light scattering in order to characterize the structure and chemical composition of in-house and commercially available materials. These methods allow us to measure key parameters to assess material quality such as flake thickness and lateral size, carbon to oxygen ratio and impurity content. Conductivity and work function of ultrathin films produced from various graphene and graphene oxide containing dispersions have been also measured. The performance of these films as transparent conductors can be characterized by a figure of merit based on the optical transmission and conductivity of the film. Performance of films made via reduction of GO will be compared with those based on graphene exfoliated without oxidation. Recently we have begun to extend this work to dispersions of other two-dimensional materials such as the transition metal dichalcogenides (TMDC). Initial characterization of commercially available TMDCs will be presented.

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Yang, Cheng-Hsien, and Shu-Tong Chang. "First-Principles Study of the Optical Properties of TMDC/Graphene Heterostructures." Photonics 9, no. 6 (May 30, 2022): 387. http://dx.doi.org/10.3390/photonics9060387.

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The transition-metal dichalcogenide (TMDC) in the family of MX2 (M=Mo,W; X=S,Se) and the graphene (Gr) monolayer are an atomically thin semiconductor and a semimetal, respectively. The monolayer MX2 has been discovered as a new class of semiconductors for electronics and optoelectronics applications. Because of the hexagonal lattice structure of both materials, MX2 and Gr are often combined with each other to generate van der Waals heterostructures. Here, the MX2/Gr heterostructures are investigated theoretically based on density functional theory (DFT). The electronic structure and the optical properties of four different MX2/Gr heterostructures are computed. We systematically compare these MX2/Gr heterostructures for their complex permittivity, absorption coefficient, reflectivity and refractive index.

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49

Fan, Xiao-Li, Yu-Rong An, Zhi-Fen Luo, Yan Hu, Bai-Hai Li, and Woon-Ming Lau. "3-Fold-Periodic Size-Dependence in Electronic Properties of Monolayer-TMDC Nanotriangles." Journal of Physical Chemistry Letters 9, no. 6 (March 5, 2018): 1346–52. http://dx.doi.org/10.1021/acs.jpclett.8b00449.

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50

Ghimire, Rupesh, Fatemeh Nematollahi, Jhih-Sheng Wu, Vadym Apalkov, and Mark I. Stockman. "TMDC-Based Topological Nanospaser: Single and Double Threshold Behavior." ACS Photonics 8, no. 3 (February 26, 2021): 907–15. http://dx.doi.org/10.1021/acsphotonics.0c01919.

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Journal articles on the topic 'TMDC materials'

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