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1. 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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2. Mineralogical and physical studies of low-grade tantalum-tin ores from selected areas of Rwanda

   https://doi.org/10.1016/j.rineng.2021.100248  

   Habinshuti, Jean Baptiste ; Munganyinka, Jeanne Pauline ; Adetunji, Adelena R. ; Mishra, Brajendra ; Ofori-Sarpong, Grace ; Komadja, Gbetoglo Charles ; Tanvar, Himanshu ; Mukiza, Janvier ; Onwualu, Azikiwe P. ( September 2021 , Results in Engineering)

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3. Catalytic intramolecular hydroamination of aminoallenes using titanium and tantalum complexes of sterically encumbered chiral sulfonamides

   https://doi.org/10.1039/D0DT02557G  

   Sha, Fanrui ; Shimizu, Emily A. ; Slocumb, Hannah S. ; Towell, Sydney E. ; Zhen, Yi ; Porter, Hanna Z. ; Takase, Michael ; Johnson, Adam ( January 2020 , Dalton Transactions)

   Catalysis using earth abundant metals is an important goal due to the relative scarcity and expense of precious metal catalysts. It would be even more beneficial to use earth abundant catalysts for the synthesis of common pharmaceutical structural motifs such as pyrrolidine and pyridine. Thus, developing titanium catalysts for asymmetric ring closing hydroamination is a valuable goal. In this work, four sterically encumbered chiral sulfonamides derived from naturally occurring amino acids were prepared. These compounds undergo protonolysis reactions with Ti(NMe 2 ) 4 or Ta(NMe 2 ) 5 to give monomeric complexes as determined by both DOSY NMR and X-ray crystallography. The resulting complexes are active for the ring closing hydroamination hepta-4,5-dienylamine to give a mixture of tetrahydropyridine and pyrrolidine products. However, the titanium complexes convert 6-methylhepta-4,5-dienylamine exclusively to 2-(2-methylpropenyl)pyrrolidine in higher enantioselectivity than those previously reported, with enantiomeric excesses ranging from 18-24%. The corresponding tantalum complexes were more selective with enantiomeric excesses ranging from 33-39%. 

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4. Selective Reduction of Niobium(V) Species to Promote Molecular Niobium/Tantalum Separation

   https://doi.org/10.1021/acs.inorgchem.1c02976  

   Furigay, Maxwell H. ; Chaudhuri, Subhajyoti ; Deresh, Sean M. ; Weberg, Alexander B. ; Pandey, Pragati ; Carroll, Patrick J. ; Schatz, George C. ; Schelter, Eric J. ( January 2022 , Inorganic Chemistry)
5. A diffusion approach for plasma synthesis of superhard tantalum borides

   https://doi.org/10.1557/jmr.2019.357  

   Rau, Aaditya ; Chakrabarty, Kallol ; Gullion, William ; Baker, Paul A. ; Bikmukhametov, Ilias ; Martens, Richard L. ; Thompson, Gregory B. ; Catledge, Shane A. ( March 2020 , Journal of Materials Research)

   Microwave plasma chemical vapor deposition (MPCVD) was used to diffuse boron into tantalum using plasma initiated from a feedgas mixture containing hydrogen and diborane. The role of substrate temperature and substrate bias in influencing surface chemical structure and hardness was investigated. X-ray diffraction shows that increased temperature results in increased TaB 2 formation (relative to TaB) along with increased strain in the tantalum body-centered cubic lattice. Once the strained tantalum becomes locally supersaturated with boron, TaB and TaB 2 precipitate. Additional boron remains in a solid solution within the tantalum. The combination of precipitation and solid solution hardening along with boron-induced lattice strain may help explain the 40 GPa average hardness measured by nanoindentation. Application of negative substrate bias did not further increase the hardness, possibly due to etching from increased ion bombardment. These results show that MPCVD is a viable method for synthesis of superhard borides based on plasma-assisted diffusion. 

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