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1. Plasma-Enhanced Atomic Layer Deposition Synthesis of Nanolayered Molybdenum Diselenide (MoSe ₂ ) Thin Films for Nanoelectronics

   https://doi.org/10.1021/acsomega.5c12568  

   Sanchez, Fabian; Giwa, Ibraheem; Chimba, Baraka; Xiao, Edward; Kisslinger, Kim; Nykypanchuk, Dmytro; Tong, Xiao; Camino, Fernando; Monikandan, Rebhadevi; Xiao, Zhigang (May 2026, ACS Omega)

   Nanolayered molybdenum diselenide (MoSe2) thin films were synthesized by plasma-enhanced atomic layer deposition (PE-ALD) using molybdenum pentachloride (MoCl5) and diethyldiselenide (C4H10Se2) precursors. Scanning and transmission electron microscopy revealed horizontally stacked nanolayers near the substrate and vertically oriented nanosheets at the surface of the film. X-ray diffraction confirmed the (002), (100), and (110) reflections of crystalline MoSe2, while X-ray photoelectron spectroscopy showed relative atomic concentrations of 33.5% Mo and 66.5% Se, consistent with stoichiometric MoSe2. Raman spectra exhibited characteristic E1g, A1g, and E12g vibrational modes. Field-effect transistors incorporating PE-ALD-grown MoSe2 as the channel material displayed p-type behavior, demonstrating the potential of nanolayered MoSe2 for nanoelectronic applications. This work demonstrates the feasibility of low-temperature, stoichiometric growth of nanolayered MoSe2 by PE-ALD and its direct integration into transistor architectures. 

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2. Electronic reconstruction in confined ${\mathrm{SrRuO}}_3$ monolayers

   https://doi.org/10.1103/PhysRevB.110.235104  

   Lamichhane, U; Sankhi, B; Kundu, N; Fabbris, G; Choi, Y; Haskel, D; McChesney, J L; Cao, Yue; Li, J; Bisogni, V; et al (December 2024, Physical Review B)

   We report the observation of an electronic reconstruction in dimensionally controlled ruthenate heterostructures synthesized by pulsed laser deposition. High structural and electronic quality of superlattices comprised of a single SrRuO3 layer inter-spaced with varying thicknesses of insulating SrTiO3 layers was verified by reflection high energy electron diffraction, atomic force microscopy, x-ray diffraction, reciprocal space mapping, and x-ray absorption spectroscopy. X-ray absorption spectroscopy evidences a confinement-driven evolution of the Ru electronic configuration from the d5L to the d4 state. Significant increases of the spin-orbit coupling are observed in connection with the configuration changes supporting recent works identifying large enhancement of the magnetic anisotropy. The growth of high quality two-dimensional confined ruthenate layers under precisely controlled environments highlights the potential to directly manipulate interlayer coupling and selectively perturb the electronic state in ruthenates in analogy to superconducting Sr2RuO4. 

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3. Strain-controlled superconductivity in few-layer NbSe2

   C. Chen, P. Das (July 2020, ACS applied materials interfaces)

   The controlled tunability of superconductivity in low-dimensional materials may enable new quantum devices. Particularly in triplet or topological superconductors, tunneling devices such as Josephson junctions, etc., can demonstrate exotic functionalities. The tunnel barrier, an insulating or normal material layer separating two superconductors, is a key component for the junctions. Thin layers of NbSe2 have been shown as a superconductor with strong spin orbit coupling, which can give rise to topological superconductivity if driven by a large magnetic exchange field. Here we demonstrate the superconductor−insulator transitions in epitaxially grown few-layer NbSe2 with wafer-scale uniformity on insulating substrates. We provide the electrical transport, Raman spectroscopy, cross-sectional transmission electron microscopy, and X-ray diffraction characterizations of the insulating phase. We show that the superconductor−insulator transition is driven by strain, which also causes characteristic energy shifts of the Raman modes. Our observation paves the way for high-quality heterojunction tunnel barriers to be seamlessly built into epitaxial NbSe2 itself, thereby enabling highly scalable tunneling devices for superconductor-based quantum electronics. 

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4. Growth of Highly Oriented (VNbMoTaW)S ₂ Layers

   https://doi.org/10.1021/acs.nanolett.3c04521  

   Tanaka, Koichi; Zaid, Hicham; Aoki, Toshihiro; Deshpande, Aditya; Hojo, Koki; Ciobanu, Cristian V; Kodambaka, Suneel (January 2024, Nano Letters)

   Compositional tunability, an indispensable parameter to modify materials' properties, can open up new applications for the class of van der Waals (vdW) layered materials such as transition-metal dichalcogenides (TMDCs). To-date, multi-element alloy TMDC layers are obtained via exfoliation from bulk polycrystalline powders. Here, we demonstrate direct deposition of high-entropy alloy disulfide, (VNbMoTaW)S2, layers with controllable thicknesses on free-standing graphene membranes and on bare and hBN-covered Al2O3(0001) substrates via ultra-high vacuum reactive dc magnetron sputtering of VNbMoTaW target in Kr and H2S gas mixtures. Using a combination of density functional theory calculations, Raman spectroscopy, X-ray diffraction, scanning transmission electron microscopy coupled with energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy, we determine that the as-deposited layers are single-phase, 2H-structured, and 0001-oriented (V0.10Nb0.16Mo0.19Ta0.28W0.27)S2.44. Our synthesis route is general and applicable for heteroepitaxial growth of a wide variety of TMDC alloys and potentially other multielement alloy vdW compounds with the desired compositions. 

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5. Temperature−Dependent Raman Scattering Investigation on vdW Epitaxial PbI2/CrOCl Heterostructure

   https://doi.org/10.3390/cryst13010104  

   You, Siwen; Guo, Xiao; Jiang, Junjie; Yang, Dingbang; Li, Mingjun; Ouyang, Fangping; Xie, Haipeng; Huang, Han; Gao, Yongli (January 2023, Crystals)

   Van der Waals (vdW) epitaxial growth provides an efficient strategy to prepare heterostructures with atomically and electronically sharp interfaces. Herein, PbI2 was in situ thermally deposited onto exfoliated thin−layered CrOCl nanoflakes in high vacuum to fabricate vdW PbI2/CrOCl heterostructures. Optical microscopy, atomic force microscopy, X−ray diffraction, and temperature−dependent Raman spectroscopy were used to investigate the structural properties and phonon behaviors of the heterostructures. The morphology of PbI2 films on the CrOCl substrate obviously depended on the substrate temperature, changing from hemispherical granules to 2D nanoflakes with flat top surfaces. In addition, anomalous blueshift of the Ag1 and Au2 modes as the temperature increased in PbI2/CrOCl heterostructure was observed for the first time. Our results provide a novel material platform for the vdW heterostructure and a possible method for optimizing heterostructure growth behaviors. 

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