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1. Sulfur Vacancy Related Optical Transitions in Graded Alloys of Mo x W 1‐x S 2 Monolayers

   https://doi.org/10.1002/adom.202302326  

   Ghafariasl, Mahdi ; Zhang, Tianyi ; Ward, Zachary D. ; Zhou, Da ; Sanchez, David ; Swaminathan, Venkataraman ; Terrones, Humberto ; Terrones, Mauricio ; Abate, Yohannes ( February 2024 , Advanced Optical Materials)

   Engineering electronic bandgaps is crucial for applications in information technology, sensing, and renewable energy. Transition metal dichalcogenides (TMDCs) offer a versatile platform for bandgap modulation through alloying, doping, and heterostructure formation. Here, the synthesis of a 2D Mo_xW_1‐xS₂graded alloy is reported, featuring a Mo‐rich center that transitions to W‐rich edges, achieving a tunable bandgap of 1.85 to 1.95 eV when moving from the center to the edge of the flake. Aberration‐corrected high‐angle annular dark‐field scanning transmission electron microscopy showed the presence of sulfur monovacancy, V_S, whose concentration varied across the graded Mo_xW_1‐xS₂layer as a function of Mo content with the highest value in the Mo‐rich center region. Optical spectroscopy measurements supported by ab initio calculations reveal a doublet electronic state of V_S, which is split due to the spin‐orbit interaction, with energy levels close to the conduction band or deep in the bandgap depending on whether the vacancy is surrounded by W atoms or Mo atoms. This unique electronic configuration of V_Sin the alloy gave rise to four spin‐allowed optical transitions between the V_Slevels and the valence bands. The study demonstrates the potential of defect and optical engineering in 2D monolayers for advanced device applications.

    

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2. Corrosion Behavior and Hardness of Binary Mg Alloys Produced via High-Energy Ball-Milling and Subsequent Spark Plasma Sintering

   https://doi.org/10.5006/3633  

   Farooq Khan, Mohammad Umar ; Larimian, Taban ; Borkar, T. ; Gupta, R.K. ( November 2020 , Corrosion)

   null (Ed.)

   In this work, nine nanocrystalline binary Mg alloys were synthesized by high-energy ball milling. The compositions, Mg-5 wt% M (M-Cr, Ge, Mn, Mo, Ta, Ti, V, Y, and Zn), were milled with the objective of achieving non-equilibrium alloying. The milled alloys were consolidated via cold compaction (CC) at 25°C and spark plasma sintering (SPS) at 300°C. X-ray diffraction (XRD) analysis indicated grain refinement below 100 nm, and the scanning electron microscopy revealed homogeneous microstructures for all compositions. XRD analysis revealed that most of the alloys showed a change in the lattice parameter, which indicates the formation of a solid solution. A significant increase in the hardness compared to unmilled Mg was observed for all of the alloys. The corrosion behavior was improved in all of the binary alloys compared to milled Mg. A significant decrease in the cathodic kinetics was evident due to Ge and Zn additions. The influence of the alloying elements on corrosion behavior has been categorized and discussed based on the electrochemical response of their respective binary Mg alloys. 

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3. Electrical Detection and Magnetic Imaging of Stabilized Magnetic Skyrmions in Fe 1− x Co x Ge ( x < 0.1) Microplates

   https://doi.org/10.1002/adfm.201805418  

   Stolt, Matthew J. ; Schneider, Sebastian ; Mathur, Nitish ; Shearer, Melinda J. ; Rellinghaus, Bernd ; Nielsch, Kornelius ; Jin, Song ( February 2019 , Advanced Functional Materials)

   Magnetic skyrmions are topologically protected spin textures that are being investigated for their potential use in next generation magnetic storage devices. Here, magnetic skyrmions and other magnetic phases in Fe_1−xCo_xGe (x< 0.1) microplates (MPLs) newly synthesized via chemical vapor deposition are studied using both magnetic imaging and transport measurements. Lorentz transmission electron microscopy reveals a stabilized magnetic skyrmion phase near room temperature (≈280 K) and a quenched metastable skyrmion lattice via field cooling. Magnetoresistance (MR) measurements in three different configurations reveal a unique anomalous MR signal at temperatures below 200 K and two distinct field dependent magnetic transitions. The topological Hall effect (THE), known as the electronic signature of magnetic skyrmion phase, is detected for the first time in a Fe_1−xCo_xGe nanostructure, with a large and positive peak THE resistivity of ≈32 nΩ cm at 260 K. This large magnitude is attributed to both nanostructuring and decreased carrier concentrations due to Co alloying of the Fe_1−xCo_xGe MPL. A consistent magnetic phase diagram summarized from both the magnetic imaging and transport measurements shows that the magnetic skyrmions are stabilized in Fe_1−xCo_xGe MPLs compared to bulk materials. This study lays the foundation for future skyrmion‐based nanodevices in information storage technologies.

    

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4. Dimetalloylene (M‐E‐M) Complexes of Heavier Main Group Elements Ge, Sn, Pb, Bi via Cleavage of E‐X Bonds (X=N(SiMe 3 ) 2 , O t Bu) with an Iridium Hydride

   https://doi.org/10.1002/chem.202301863  

   Saint‐Denis, Tyler G. ; Zhang, Bowen ; Settineri, Nicholas S. ; Handford, Rex C. ; Hall, Michael B. ; Tilley, T. Don ( July 2023 , Chemistry – A European Journal)

   Reactions of the Ir^Vhydride [^MeBDI^Dipp]IrH₄{BDI=(Dipp)NC(Me)CH(Me)CN(Dipp); Dipp=2,6‐iPr₂C₆H₃} with E[N(SiMe₃)₂]₂(E=Sn, Pb) afforded the unusual dimeric dimetallotetrylenes ([^MeBDI^Dipp]IrH)₂(μ₂‐E)₂in good yields. Moreover, ([^MeBDI^Dipp]IrH)₂(μ₂‐Ge)₂was formed in situ from thermal decomposition of [^MeBDI^Dipp]Ir(H)₂Ge[N(SiMe₃)₂]₂. These reactions are accompanied by liberation of HN(SiMe₃)₂and H₂through the apparent cleavage of an E−N(SiMe₃)₂bond by Ir−H. In a reversal of this process, ([^MeBDI^Dipp]IrH)₂(μ₂‐E)₂reacted with excess H₂to regenerate [^MeBDI^Dipp]IrH₄. Varying the concentrations of reactants led to formation of the trimeric ([^MeBDI^Dipp]IrH₂)₃(μ₂‐E)₃. The further scope of this synthetic route was investigated with group 15 amides, and ([^MeBDI^Dipp]IrH)₂(μ₂‐Bi)₂was prepared by the reaction of [^MeBDI^Dipp]IrH₄with Bi(NMe₂)₃or Bi(OtBu)₃to afford the first example of a “naked” two‐coordinate Bi atom bound exclusively to transition metals. A viable mechanism that accounts for the formation of these products is proposed. Computational investigations of the Ir₂E₂(E=Sn, Pb) compounds characterized them as open‐shell singlets with confined nonbonding lone pairs at the E centers. In contrast, Ir₂Bi₂is characterized as having a closed‐shell singlet ground state.

    

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5. Improved Thermoelectric Performance of Eco‐Friendly β‐FeSi 2 –SiGe Nanocomposite via Synergistic Hierarchical Structuring, Phase Percolation, and Selective Doping

   https://doi.org/10.1002/adfm.201903157  

   Liu, Naiming ; Rezaei, S. Emad ; Jensen, Wade Aaron ; Song, Shaowei ; Ren, Zhifeng ; Esfarjani, Keivan ; Zebarjadi, Mona ; Floro, Jerrold Anthony ( July 2019 , Advanced Functional Materials)

   A β‐FeSi₂–SiGe nanocomposite is synthesized via a react/transform spark plasma sintering technique, in which eutectoid phase transformation, Ge alloying, selective doping, and sintering are completed in a single process, resulting in a greatly reduced process time and thermal budget. Hierarchical structuring of the SiGe secondary phase to achieve coexistence of a percolated network with isolated nanoscale inclusions effectively decouples the thermal and electrical transport. Combined with selective doping that reduces conduction band offsets, the percolation strategy produces overall electron mobilities 30 times higher than those of similar materials produced using typical powder‐processing routes. As a result, a maximum thermoelectric figure of meritZTof ≈0.7 at 700 °C is achieved in the β‐FeSi₂–SiGe nanocomposite.

    

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