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1. Influence of Rhenium Concentration on Charge Doping and Defect Formation in MoS ₂

   https://doi.org/10.1002/aelm.202400403  

   Munson, Kyle T; Torsi, Riccardo; Habis, Fatimah; Huberich, Lysander; Lin, Yu‐Chuan; Yuan, Yue; Wang, Ke; Schuler, Bruno; Wang, Yuanxi; Asbury, John B; et al (March 2025, Advanced Electronic Materials)

   Substitutionally doped transition metal dichalcogenides (TMDs) are essential for advancing TMD‐based field effect transistors, sensors, and quantum photonic devices. However, the impact of local dopant concentrations and dopant–dopant interactions on charge doping and defect formation within TMDs remains underexplored. Here, a breakthrough understanding of the influence of rhenium (Re) concentration is presented on charge doping and defect formation in MoS₂monolayers grown by metal–organic chemical vapor deposition (MOCVD). It is shown that Re‐MoS₂films exhibit reduced sulfur‐site defects, consistent with prior reports. However, as the Re concentration approaches ⪆2 atom%, significant clustering of Re in the MoS₂is observed. Ab Initio calculations indicate that the transition from isolated Re atoms to Re clusters increases the ionization energy of Re dopants, thereby reducing Re‐doping efficacy. Using photoluminescence (PL) spectroscopy, it is shown that Re dopant clustering creates defect states that trap photogenerated excitons within the MoS₂lattice, resulting in broad sub‐gap emission. These results provide critical insights into how the local concentration of metal dopants influences carrier density, defect formation, and exciton recombination in TMDs, offering a novel framework for designing future TMD‐based devices with improved electronic and photonic properties. 

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2. Temperature‐Dependent Optical and Polaritonic Properties of Excitons in hBN‐Encapsulated Monolayer TMDs

   https://doi.org/10.1002/adom.202502535  

   Meshulam, Matan; Kahlon, Anabel Atash; Gershuni, Yonatan; Poirier, Thomas; Edgar, James H; Tongay, Seth Ariel; Epstein, Itai (February 2026, Advanced Optical Materials)

   Abstract Monolayer transition metal dichalcogenides (TMDs) support robust excitons in the visible to near‐infrared spectral range. Their reduced dielectric screening results in large binding energies, and combined with a direct bandgap in monolayer form, these excitons dominate the optical response of TMDs. In this work, a comprehensive investigation of the temperature‐dependent optical and polaritonic properties of high‐quality WS₂, MoS₂, WSe₂, and MoSe₂monolayers, encapsulated by hBN, in the range of 5‐300 K, is presented. Using reflection spectroscopy measurements, the optical and polaritonic constituents of the TMD excitons in terms of oscillator strength, linewidth, and negative permittivity, are evaluated and compared. It is found that MoSe₂exhibits the most pronounced optical and polaritonic response, stemming from its rapid linewidth narrowing at low temperatures, as compared to the other TMDs. In addition, It is found that all four TMDs exhibit a temperature‐dependent negative real part permittivity, thus supporting surface‐exciton‐polaritons. The dispersion relation, confinement factor, and losses are derived and similarly reveal that MoSe₂exhibits enhanced polaritonic properties. These findings establish a comparative framework for understanding the optical and polaritonic properties of monolayer TMDs, with implications on their utilization in optoelectronic devices based on 2D semiconductors. 

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3. Sodium and potassium ion storage in cation substituted 2D MoWSe ₂ : insights into the effects of upper voltage cut-off

   https://doi.org/10.1088/1361-6528/acdf66  

   Dey, Sonjoy; Singh, Gurpreet (July 2023, Nanotechnology)

   Abstract The superior properties, such as large interlayer spacing and the ability to host large alkali-metal ions, of two-dimensional (2D) materials based on transition metal di-chalcogenides (TMDs) enable next-generation battery development beyond lithium-ion rechargeable batteries. In addition, compelling but rarely inspected TMD alloys provide additional opportunities to tailor bandgap and enhance thermodynamic stability. This study explores the sodium-ion (Na-ion) and potassium-ion (K-ion) storage behavior of cation-substituted molybdenum tungsten diselenide (MoWSe₂), a TMD alloy. This research also investigates upper potential suspension to overcome obstacles commonly associated with TMD materials, such as capacity fading at high current rates, prolonged cycling conditions, and voltage polarization during conversion reaction. The voltage cut-off was restricted to 1.5 V, 2.0 V, and 2.5 V to realize the material’s Na⁺and K⁺ion storage behavior. Three-dimensional (3D) surface plots of differential capacity analysis up to prolonged cycles revealed the convenience of voltage suspension as a viable method for structural preservation. Moreover, the cells with higher potential cut-off values conveyed improved cycling stability, higher and stable coulombic efficiency for Na⁺and K⁺ion half-cells, and increased capacity retention for Na⁺ion half-cells, respectively, with half-cells cycled at higher voltage ranges. 

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4. Origins of Fermi Level Pinning for Ni and Ag Metal Contacts on Tungsten Dichalcogenides

   https://doi.org/10.1021/acsnano.3c06494  

   Wang, Xinglu; Hu, Yaoqiao; Kim, Seong Yeoul; Addou, Rafik; Cho, Kyeongjae; Wallace, Robert M (October 2023, ACS Nano)

   Tungsten transition metal dichalcogenides (W-TMDs) are intriguing due to their properties and potential for application in next-generation electronic devices. However, strong Fermi level (EF) pinning manifests at the metal/W-TMD interfaces, which could tremendously restrain the carrier injection into the channel. In this work, we illustrate the origins of EF pinning for Ni and Ag contacts on W-TMDs by considering interface chemistry, band alignment, impurities, and imperfections of W-TMDs, contact metal adsorption mechanism, and the resultant electronic structure. We conclude that the origins of EF pinning at a covalent contact metal/W-TMD interface, such as Ni/W-TMDs, can be attributed to defects, impurities, and interface reaction products. In contrast, for a van der Waals contact metal/TMD system such as Ag/W-TMDs, the primary factor responsible for EF pinning is the electronic modification of the TMDs resulting from the defects and impurities with the minor impact of metal-induced gap states. The potential strategies for carefully engineering the metal deposition approach are also discussed. This work unveils the origins of EF pinning at metal/TMD interfaces experimentally and theoretically and provides guidance on further enhancing and improving the device performance. 

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5. Wafer-Scale Epitaxial Growth of Unidirectional WS2 Monolayers on Sapphire

   https://doi.org/https://doi.org/10.1021/acsnano.0c06750  

   Chubarov, Mikhail; Choudhury, Tanushree H.; Hickey, Danielle Reifsnyder; Bachu, Saiphaneendra; Zhang, Tianyi; Sebastian, Amritanand; Bansal, Anushka; Zhu, Haoyue; Trainor, Nicholas; Das, Saptarshi; et al (January 2021, ACS nano)

   null (Ed.)

   Realization of wafer-scale single-crystal films of transition metal dichalcogenides (TMDs) such as WS2 requires epitaxial growth and coalescence of oriented domains to form a continuous monolayer. The domains must be oriented in the same crystallographic direction on the substrate to inhibit the formation of inversion domain boundaries (IDBs), which are a common feature of layered chalcogenides. Here we demonstrate fully coalesced unidirectional WS2 monolayers on 2 in. diameter c-plane sapphire by metalorganic chemical vapor deposition using a multistep growth process to achieve epitaxial WS2 monolayers with low in-plane rotational twist (0.09°). Transmission electron microscopy analysis reveals that the WS2 monolayers are largely free of IDBs but instead have translational boundaries that arise when WS2 domains with slightly offset lattices merge together. By regulating the monolayer growth rate, the density of translational boundaries and bilayer coverage were significantly reduced. The unidirectional orientation of domains is attributed to the presence of steps on the sapphire surface coupled with growth conditions that promote surface diffusion, lateral domain growth, and coalescence while preserving the aligned domain structure. The transferred WS2 monolayers show neutral and charged exciton emission at 80 K with negligible defect-related luminescence. Back-gated WS2 field effect transistors exhibited an ION/OFF of ∼107 and mobility of 16 cm2/(V s). The results demonstrate the potential of achieving wafer-scale TMD monolayers free of inversion domains with properties approaching those of exfoliated flakes. 

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