The understanding on the mechanical properties of graphene under the applications of physical fields is highly relevant to the reliability and lifetime of graphene-based nanodevices. In this work, we demonstrate that the application of electric field could soften the mechanical properties of graphene dramatically on the basis of the conductive AFM nanoindentation method. It has been found that the Young’s modulus and fracture strength of graphene nanosheets suspended on the holes almost stay the same initially and then exhibit a sharp drop when the normalized electric field strength increases to be 0.18 ± 0.03 V/nm. The threshold voltage of graphene nanosheets before the onset of fracture under the fixed applied load increases with the thickness. Supported graphene nanosheets can sustain larger electric field under the same applied load than the suspended ones. The excessively regional Joule heating caused by the high electric current under the applied load is responsible for the electromechanical failure of graphene. These findings can provide a beneficial guideline for the electromechanical applications of graphene-based nanodevices.

中文翻译：

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电场诱导石墨烯的软化力学性能

在物理领域的应用下对石墨烯机械性能的了解与石墨烯基纳米器件的可靠性和使用寿命高度相关。在这项工作中，我们证明在导电AFM纳米压痕方法的基础上，电场的施加可以显着软化石墨烯的机械性能。已经发现，悬浮在孔上的石墨烯纳米片的杨氏模量和断裂强度最初几乎保持不变，然后当归一化电场强度增加到0.18±0.03 V / nm时呈现急剧下降。在固定施加的载荷下，断裂开始前的石墨烯纳米片的阈值电压随厚度的增加而增加。负载的石墨烯纳米片在相同的施加负载下可以比悬浮的纳米片承受更大的电场。在施加负载的情况下，高电流导致的过高的焦耳局部加热是石墨烯机电故障的原因。这些发现可以为基于石墨烯的纳米器件的机电应用提供有益的指导。