講演情報
[16p-PA7-11]In situ TEM Observation of Ductile-like Fracture in MoS2 nanosheet Under Strain
〇(PC)Wei Xiong1, Yoshifumi Oshima1 (1.JAIST)
キーワード：
In situ TEM、Tensile fracture、Molybdenum disulfide
Research into electronic devices and sensors using two-dimensional materials is being vigorously pursued. For sensors, since they utilize the resonance of two-dimensional materials, understanding the fracture process is essential for evaluating their design and reliability. Consequently, studies are being conducted to determine whether fracture occurs brittlely from microdefects or ductilely, involving dislocation motion, defect generation, and localized structural changes. Ly et al. argue that while single-layer MoS2 fundamentally fractures brittlely, high-speed dislocation motion in and out of the crack tip's micro-region indicates plastic behavior (ductile process). Previously, we developed in situ TEM holder equipped with a stretching function. The evolution of ripple structures and the fracture processes under tensile strain was observed. In this study, we observed a ductile fracture process of MoS2 nanosheet under strain by this TEM holder.
The MoS2 nanosheets were obtained from bulk MoS2 crystals by mechanical exfoliation. After an all-dry transfer process, the exfoliated nanosheets were transferred onto the observation region of the tensile platform, resulting in a suspended MoS2 nanosheet suitable for tensile testing. The in-situ tensile experiments were conducted using a JEOL TEM-2100Plus operated at an accelerating voltage of 120 kV.
We observed that pre-existing defects or electron beam induced defects formed a void and that void migrated toward the step edge with the layer whose crystal orientation was rotated (twisted layer). Such voids were aligned along the step edge, resulting in rupture of the nanosheet. By geometrical phase analysis, the stress was found to concentrate along the step edge with the twisted layer. In contrast, the voids were not observed to be penetrated in the regions of the twisted layer and the edge was rolled after breaking the nanosheet along the edge.
The MoS2 nanosheets were obtained from bulk MoS2 crystals by mechanical exfoliation. After an all-dry transfer process, the exfoliated nanosheets were transferred onto the observation region of the tensile platform, resulting in a suspended MoS2 nanosheet suitable for tensile testing. The in-situ tensile experiments were conducted using a JEOL TEM-2100Plus operated at an accelerating voltage of 120 kV.
We observed that pre-existing defects or electron beam induced defects formed a void and that void migrated toward the step edge with the layer whose crystal orientation was rotated (twisted layer). Such voids were aligned along the step edge, resulting in rupture of the nanosheet. By geometrical phase analysis, the stress was found to concentrate along the step edge with the twisted layer. In contrast, the voids were not observed to be penetrated in the regions of the twisted layer and the edge was rolled after breaking the nanosheet along the edge.