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- ItemLateral Selective SiGe Growth for Local Dislocation-Free SiGe-on-Insulator Virtual Substrate Fabrication(Pennington, NJ : ECS, 2023) Anand, K.; Schubert, M.A.; Corley-Wiciak, A.A.; Spirito, D.; Corley-Wiciak, C.; Klesse, W.M.; Mai, A.; Tillack, B.; Yamamoto, Y.Dislocation free local SiGe-on-insulator (SGOI) virtual substrate is fabricated using lateral selective SiGe growth by reduced pressure chemical vapor deposition. The lateral selective SiGe growth is performed around a ∼1.25 μm square Si (001) pillar in a cavity formed by HCl vapor phase etching of Si at 850 °C from side of SiO2/Si mesa structure on buried oxide. Smooth root mean square roughness of SiGe surface of 0.14 nm, which is determined by interface roughness between the sacrificially etched Si and the SiO2 cap, is obtained. Uniform Ge content of ∼40% in the laterally grown SiGe is observed. In the Si pillar, tensile strain of ∼0.65% is found which could be due to thermal expansion difference between SiO2 and Si. In the SiGe, tensile strain of ∼1.4% along 〈010〉 direction, which is higher compared to that along 〈110〉 direction, is observed. The tensile strain is induced from both [110] and [−110] directions. Threading dislocations in the SiGe are located only ∼400 nm from Si pillar and stacking faults are running towards 〈110〉 directions, resulting in the formation of a wide dislocation-free area in SiGe along 〈010〉 due to horizontal aspect ratio trapping.
- ItemLocal Structure Investigation of Cu Precipitates in Modified 18CrNiMo7-6 Steels by Synchrotron X-ray Absorption Spectroscopy(Tōkyō : ISIJ, 2022) Suwanpinij, Piyada; Bambach, Margarita; Bootchanont, Atipong; Sailuam, WutthigraiThis paper studied the copper precipitation in an 18CrNiMo7-6 martensitic steel (0.19 mass% C) with copper addition and its resulting improved mechanical behavior. The development of nano-precipitates in two modified alloys with 1.0 and 1.5 mass% copper addition was investigated by means of synchrotron X-ray absorption spectroscopy. The first-principles calculation has enabled the modeling of the unavailable copper standards: solid solution, B2, BCC, 2H, 9R and 3R, for calculating the XAS spectra and successfully identified the unknown phases after aging for the first time in this steel group. The samples alloyed with 1.5 mass% copper yielded the semi-coherent 9R structure when aged at 500°C between 166 to 360 minutes. The ones containing 1 mass% copper formed the B2 ordered structure after aging at 480°C for 50 minutes and revealed the co-existence of the 9R after 240 minutes. The analysis reveals the precipitation kinetics of copper in low carbon martensitic steel and helps determine the optimum tempering parameters to adjust peak strength.
- ItemFreestanding MXene‐based macroforms for electrochemical energy storage applications(Hoboken, NJ : Wiley, 2023) Lu, Qiongqiong; Liu, Congcong; Zhao, Yirong; Pan, Wengao; Xie, Kun; Yue, Pengfei; Zhang, Guoshang; Omar, Ahmad; Liu, Lixiang; Yu, Minghao; Mikhailova, DariaFreestanding MXene-based macroforms have gained significant attention as versatile components in electrochemical energy storage applications owing to their interconnected conductive network, strong mechanical strength, and customizable surface chemistries derived from MXene nanosheets. This comprehensive review article encompasses key aspects related to the synthesis of MXene nanosheets, strategies for structure design and surface medication, surface modification, and the diverse fabrication methods employed to create freestanding MXene-based macroform architectures. The review also delves into the recent advancements in utilizing freestanding MXene macroforms for electrochemical energy storage applications, offering a detailed discussion on the significant progress achieved thus far. Notably, the correlation between the macroform's structural attributes and its performance characteristics is thoroughly explored, shedding light on the critical factors influencing efficiency and durability. Despite the remarkable development, the review also highlights the existing challenges and presents future perspectives for freestanding MXene-based macroforms in the realms of high-performance energy storage devices. By addressing these challenges and leveraging emerging opportunities, the potential of freestanding MXene-based macroforms can be harnessed to enable groundbreaking advancements in the field of energy storage.