Agrawal Ravi, Peng Bei, Gdoutos Eleftherios E, Espinosa Horacio D
Department of Mechanical Engineering, 2145 Sheridan Road, Northwestern University, Evanston, Illinois 60208-3111, USA.
Nano Lett. 2008 Nov;8(11):3668-74. doi: 10.1021/nl801724b. Epub 2008 Oct 8.
Understanding the mechanical properties of nanowires made of semiconducting materials is central to their application in nano devices. This work presents an experimental and computational approach to unambiguously quantify size effects on the Young's modulus, E, of ZnO nanowires and interpret the origin of the scaling. A micromechanical system (MEMS) based nanoscale material testing system is used in situ a transmission electron microscope to measure the Young's modulus of [0001] oriented ZnO nanowires as a function of wire diameter. It is found that E increases from approximately 140 to 160 GPa as the nanowire diameter decreases from 80 to 20 nm. For larger wires, a Young's modulus of approximately 140 GPa, consistent with the modulus of bulk ZnO, is observed. Molecular dynamics simulations are carried out to model ZnO nanowires of diameters up to 20 nm. The computational results demonstrate similar size dependence, complementing the experimental findings, and reveal that the observed size effect is an outcome of surface reconstruction together with long-range ionic interactions.
了解由半导体材料制成的纳米线的力学性能是其在纳米器件中应用的核心。这项工作提出了一种实验和计算方法，用于明确量化尺寸对ZnO纳米线杨氏模量E的影响，并解释这种尺度效应的起源。基于微机电系统（MEMS）的纳米级材料测试系统被用于原位透射电子显微镜，以测量[0001]取向的ZnO纳米线的杨氏模量随线径的变化。结果发现，随着纳米线直径从80纳米减小到20纳米，E从约140吉帕增加到160吉帕。对于较大的纳米线，观察到约140吉帕的杨氏模量，与块状ZnO的模量一致。进行了分子动力学模拟，以模拟直径达20纳米的ZnO纳米线。计算结果显示出类似的尺寸依赖性，补充了实验结果，并揭示观察到的尺寸效应是表面重构以及长程离子相互作用的结果。
