Ripplocations in van der Waals Layers

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• 作者：Akihiro Kushima ; Xiaofeng Qian ; Peng Zhao ; Sulin Zhang ; Ju Li
• 刊名：Nano Letters
• 出版年：2015
• 出版时间：February 11, 2015
• 年：2015
• 卷：15
• 期：2
• 页码：1302-1308
• 全文大小：457K
• ISSN：1530-6992

文摘

Dislocations are topological line defects in three-dimensional crystals. Same-sign dislocations repel according to Frank鈥檚 rule |b₁ + b₂|² > |b₁|² + |b₂|². This rule is broken for dislocations in van der Waals (vdW) layers, which possess crystallographic Burgers vector as ordinary dislocations but feature 鈥渟urface ripples鈥?due to the ease of bending and weak vdW adhesion of the atomic layers. We term these line defects 鈥渞ipplocations鈥?in accordance to their dual 鈥渟urface ripple鈥?and 鈥渃rystallographic dislocation鈥?characters. Unlike conventional ripples on noncrystalline (vacuum, amorphous, or fluid) substrates, ripplocations tend to be very straight, narrow, and crystallographically oriented. The self-energy of surface ripplocations scales sublinearly with |b|, indicating that same-sign ripplocations attract and tend to merge, opposite to conventional dislocations. Using in situ transmission electron microscopy, we directly observed ripplocation generation and motion when few-layer MoS₂ films were lithiated or mechanically processed. Being a new subclass of elementary defects, ripplocations are expected to be important in the processing and defect engineering of vdW layers.