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1. High‐Pressure Synthesis and Thermal Conductivity of Semimetallic θ‐Tantalum Nitride

   https://doi.org/10.1002/adfm.202212957  

   Lee, Hwijong ; Zhou, Yuanyuan ; Jung, Sungyeb ; Li, Hongze ; Cheng, Zhe ; He, Jiaming ; Chen, Jie ; Sokalski, Peter ; Dolocan, Andrei ; Gearba‐Dolocan, Raluca ; et al ( February 2023 , Advanced Functional Materials)

   The lattice thermal conductivity (κ_ph) of metals and semimetals is limited by phonon‐phonon scattering at high temperatures and by electron‐phonon scattering at low temperatures or in some systems with weak phonon‐phonon scattering. Following the demonstration of a phonon band engineering approach to achieve an unusually high κ_phin semiconducting cubic‐boron arsenide (c‐BAs), recent theories have predicted ultrahigh κ_phof the semimetal tantalum nitride in the θ‐phase (θ‐TaN) with hexagonal tungsten carbide (WC) structure due to the combination of a small electron density of states near the Fermi level and a large phonon band gap, which suppress electron‐phonon and three‐phonon scattering, respectively. Here, measurements on the thermal and electrical transport properties of polycrystalline θ‐TaN converted from the ε phase via high‐pressure synthesis are reported. The measured thermal conductivity of the θ‐TaN samples shows weak temperature dependence above 200 K and reaches up to 90 Wm⁻¹K⁻¹, one order of magnitude higher than values reported for polycrystalline ε‐TaN and δ‐TaN thin films. These results agree with theoretical calculations that account for phonon scattering by 100 nm‐level grains and suggest κ_phincrease above the 249 Wm⁻¹K⁻¹value predicted for single‐crystal WC when the grain size of θ‐TaN is increased above 400 nm.

    

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2. Search for dark matter produced in association with a single top quark and an energetic W boson in $$\sqrt{s}=$$ 13 TeV $$pp$$ collisions with the ATLAS detector

   https://doi.org/10.1140/epjc/s10052-023-11582-z  

   Aad, G. ; Abbott, B. ; Abbott, D. C. ; Abeling, K. ; Abidi, S. H. ; Aboulhorma, A. ; Abramowicz, H. ; Abreu, H. ; Abulaiti, Y. ; Hoffman, A. C. ; et al ( July 2023 , The European Physical Journal C)

   This paper presents a search for dark matter,$$\chi $$$\chi$, using events with a single top quark and an energeticWboson. The analysis is based on proton–proton collision data collected with the ATLAS experiment at$$\sqrt{s}=$$$\sqrt{s}=$13 TeV during LHC Run 2 (2015–2018), corresponding to an integrated luminosity of 139 fb$$^{-1}$$${}^{-1}$. The search considers final states with zero or one charged lepton (electron or muon), at least oneb-jet and large missing transverse momentum. In addition, a result from a previous search considering two-charged-lepton final states is included in the interpretation of the results. The data are found to be in good agreement with the Standard Model predictions and the results are interpreted in terms of 95% confidence-level exclusion limits in the context of a class of dark matter models involving an extended two-Higgs-doublet sector together with a pseudoscalar mediator particle. The search is particularly sensitive to on-shell production of the charged Higgs boson state,$$H^{\pm }$$$H^{\pm }$, arising from the two-Higgs-doublet mixing, and its semi-invisible decays via the mediator particle,a:$$H^{\pm } \rightarrow W^\pm a (\rightarrow \chi \chi )$$$H^{\pm }\to W^{\pm }a(\to \chi \chi )$. Signal models with$$H^{\pm }$$$H^{\pm }$masses up to 1.5 TeV andamasses up to 350 GeV are excluded assuming a$$\tan \beta $$$tan\beta$value of 1. For masses ofaof 150 (250) GeV,$$\tan \beta $$$tan\beta$values up to 2 are excluded for$$H^{\pm }$$$H^{\pm }$masses between 200 (400) GeV and 1.5 TeV. Signals with$$\tan \beta $$$tan\beta$values between 20 and 30 are excluded for$$H^{\pm }$$$H^{\pm }$masses between 500 and 800 GeV.

    

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3. RRAM Devices with Plasma Treated HfO2 with Ru as Top Electrode for In-Memory Computing Hardware

   https://doi.org/10.1149/MA2021-0212615mtgabs  

   Patel, Y.D. ; Misra, D ; Triyoso, D.H. ; Tapily, K. ; Clark, R.D. ; Consiglio, S. ; Pattanaik, G. ; Cole, C. ; Raley, A. ; Wajda, C.S. ; et al ( January 2021 , ECS transactions)

   This work investigates the role of extra oxygen vacancies, introduced by a hydrogen plasma at midpoint of deposition of a 6 nm thick HfO2 to reduce the switching power consumption in a RRAM device. Initially TiN, which is a commonly used metal in CMOS technology, was used as the top electrode for treated HfO2. Subsequently Ru and TaN as top electrodes were explored to enhance the switching behavior and power consumption. A range of compliance currents from 1 nA to 1 µA were used to evaluate the switching characteristics. The role of both TaN and Ru as bottom metal was also evaluated. With Ru as top metal the device switched at a compliance current of 1 nA and higher. Whereas when Ru was used as bottom electrode, devices were unable to switch below a compliance current of 50 µA. For TaN as top metal electrode, devices switched at and above 1 µA CC whereas with TaN as bottom metal the initial switching was at CC of 2 µA. It was observed that use of Ru as a top metal significantly reduced the switching energy of the plasma treated HfO2 RRAM device but was ineffective when used as a bottom metal. 

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4. Enhancing Interconnect Reliability and Performance by Converting Tantalum to 2D Layered Tantalum Sulfide at Low Temperature

   https://doi.org/10.1002/adma.201902397  

   Lo, Chun‐Li ; Catalano, Massimo ; Khosravi, Ava ; Ge, Wanying ; Ji, Yujin ; Zemlyanov, Dmitry Y. ; Wang, Luhua ; Addou, Rafik ; Liu, Yuanyue ; Wallace, Robert M. ; et al ( June 2019 , Advanced Materials)

   The interconnect half‐pitch size will reach ≈20 nm in the coming sub‐5 nm technology node. Meanwhile, the TaN/Ta (barrier/liner) bilayer stack has to be >4 nm to ensure acceptable liner and diffusion barrier properties. Since TaN/Ta occupy a significant portion of the interconnect cross‐section and they are much more resistive than Cu, the effective conductance of an ultrascaled interconnect will be compromised by the thick bilayer. Therefore, 2D layered materials have been explored as diffusion barrier alternatives. However, many of the proposed 2D barriers are prepared at too high temperatures to be compatible with the back‐end‐of‐line (BEOL) technology. In addition, as important as the diffusion barrier properties, the liner properties of 2D materials must be evaluated, which has not yet been pursued. Here, a 2D layered tantalum sulfide (TaS_x) with ≈1.5 nm thickness is developed to replace the conventional TaN/Ta bilayer. The TaS_xultrathin film is industry‐friendly, BEOL‐compatible, and can be directly prepared on dielectrics. The results show superior barrier/liner properties of TaS_xcompared to the TaN/Ta bilayer. This single‐stack material, serving as both a liner and a barrier, will enable continued scaling of interconnects beyond 5 nm node.

    

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5. Genetic architecture of a body colour cline in Drosophila americana

   https://doi.org/10.1111/mec.15531  

   Sramkoski, Lisa L. ; McLaughlin, Wesley N. ; Cooley, Arielle M. ; Yuan, David C. ; John, Alisha ; Wittkopp, Patricia J. ( July 2020 , Molecular Ecology)

   Phenotypic variation within a species is often structured geographically in clines. InDrosophila americana, a longitudinal cline for body colour exists within North America that appears to be due to local adaptation. Thetanandebonygenes have been hypothesized to contribute to this cline, with alleles of both genes that lighten body colour found inD. americana. These alleles are similar in sequence and function to the allele fixed inD. americana'smore lightly pigmented sister species,Drosophila novamexicana. Here, we examine the frequency and geographic distribution of theseD. novamexicana‐like alleles inD. americana. Among alleles from over 100 strains ofD. americanaisolated from 21 geographic locations, we failed to identify additional alleles oftanorebonywith as much sequence similarity toD. novamexicanaas theD. novamexicana‐like alleles previously described. However, using genetic analysis of 51D. americanastrains derived from 20 geographic locations, we identified one new allele ofebonyand one new allele oftansegregating inD. americanathat are functionally equivalent to theD. novamexicanaallele. An additional 5 alleles oftanalso showed marginal evidence of functional similarity. Given the rarity of these alleles, however, we conclude that they are unlikely to be driving the pigmentation cline. Indeed, phenotypic distributions of the 51 backcross populations analysed indicate a more complex genetic architecture, with diversity in the number and effects of loci altering pigmentation observed both within and among populations ofD. americana. This genetic heterogeneity poses a challenge to association studies and genomic scans for clinal variation, but might be common in natural populations.

    

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