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Structural Phase Transformation in Strained Monolayer MoWSe2 Alloy
ACS Nano ( IF 15.8 ) Pub Date : 2018-02-26 00:00:00 , DOI: 10.1021/acsnano.8b00248 Amey Apte 1 , Vidya Kochat 1 , Pankaj Rajak 2 , Aravind Krishnamoorthy 2 , Praveena Manimunda 3 , Jordan A. Hachtel 4 , Juan Carlos Idrobo 4 , Syed Asif Syed Amanulla 3 , Priya Vashishta 2 , Aiichiro Nakano 2 , Rajiv K. Kalia 2 , Chandra Sekhar Tiwary 1, 5 , Pulickel M. Ajayan 1
ACS Nano ( IF 15.8 ) Pub Date : 2018-02-26 00:00:00 , DOI: 10.1021/acsnano.8b00248 Amey Apte 1 , Vidya Kochat 1 , Pankaj Rajak 2 , Aravind Krishnamoorthy 2 , Praveena Manimunda 3 , Jordan A. Hachtel 4 , Juan Carlos Idrobo 4 , Syed Asif Syed Amanulla 3 , Priya Vashishta 2 , Aiichiro Nakano 2 , Rajiv K. Kalia 2 , Chandra Sekhar Tiwary 1, 5 , Pulickel M. Ajayan 1
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Two-dimensional (2D) materials exhibit different mechanical properties from their bulk counterparts owing to their monolayer atomic thickness. Here, we have examined the mechanical behavior of 2D molybdenum tungsten diselenide (MoWSe2) precipitation alloy grown using chemical vapor deposition and composed of numerous nanoscopic MoSe2 and WSe2 regions. Applying a bending strain blue-shifted the MoSe2 and WSe2 A1g Raman modes with the stress concentrated near the precipitate interfaces predominantly affecting the WSe2 modes. In situ local Raman measurements suggested that the crack propagated primarily thorough MoSe2-rich regions in the monolayer alloy. Molecular dynamics (MD) simulations were performed to study crack propagation in an MoSe2 monolayer containing nanoscopic WSe2 regions akin to the experiment. Raman spectra calculated from MD trajectories of crack propagation confirmed the emergence of intermediate peaks in the strained monolayer alloy, mirroring experimental results. The simulations revealed that the stress buildup around the crack tip caused an irreversible structural transformation from the 2H to 1T phase both in the MoSe2 matrix and WSe2 patches. This was corroborated by high-angle annular dark-field images. Crack branching and subsequent healing of a crack branch were also observed in WSe2, indicating the increased toughness and crack propagation resistance of the alloyed 2D MoWSe2 over the unalloyed counterparts.
中文翻译：
应变单层MoWSe 2合金的结构相变
二维（2D）材料由于其单层原子厚度而具有不同于其整体材料的机械性能。在这里，我们检查了使用化学气相沉积法生长的，由许多纳米级的MoSe 2和WSe 2区域组成的2D钼二硒化钨钨（MoWSe 2）沉淀合金的力学行为。施加弯曲应变使MoSe 2和WSe 2 A 1g拉曼模式蓝移，应力集中在析出物界面附近，主要影响WSe 2模式。原位局部拉曼测量表明，裂纹主要通过MoSe 2传播。单层合金中的高富集区。进行了分子动力学（MD）模拟，以研究在包含类似于实验的纳米级WSe 2区域的MoSe 2单层中的裂纹扩展。从裂纹扩展的MD轨迹计算出的拉曼光谱证实了应变单层合金中出现中间峰，反映了实验结果。模拟结果表明，裂纹尖端周围的应力积累在MoSe 2基体和WSe 2斑块中引起了从2H到1T相的不可逆结构转变。高角度环形暗场图像证实了这一点。在WSe 2中也观察到裂纹分支和裂纹分支的后续修复，表明合金化的2D MoWSe 2的韧性和抗裂纹扩展性比未合金化的对应物有所提高。
更新日期：2018-02-26
中文翻译：
应变单层MoWSe 2合金的结构相变
二维（2D）材料由于其单层原子厚度而具有不同于其整体材料的机械性能。在这里，我们检查了使用化学气相沉积法生长的，由许多纳米级的MoSe 2和WSe 2区域组成的2D钼二硒化钨钨（MoWSe 2）沉淀合金的力学行为。施加弯曲应变使MoSe 2和WSe 2 A 1g拉曼模式蓝移，应力集中在析出物界面附近，主要影响WSe 2模式。原位局部拉曼测量表明，裂纹主要通过MoSe 2传播。单层合金中的高富集区。进行了分子动力学（MD）模拟，以研究在包含类似于实验的纳米级WSe 2区域的MoSe 2单层中的裂纹扩展。从裂纹扩展的MD轨迹计算出的拉曼光谱证实了应变单层合金中出现中间峰，反映了实验结果。模拟结果表明，裂纹尖端周围的应力积累在MoSe 2基体和WSe 2斑块中引起了从2H到1T相的不可逆结构转变。高角度环形暗场图像证实了这一点。在WSe 2中也观察到裂纹分支和裂纹分支的后续修复，表明合金化的2D MoWSe 2的韧性和抗裂纹扩展性比未合金化的对应物有所提高。
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