Tu Qing, Spanopoulos Ioannis, Yasaei Poya, Stoumpos Constantinos C, Kanatzidis Mercouri G, Shekhawat Gajendra S, Dravid Vinayak P
Department of Materials Science & Engineering , Northwestern University , Evanston , Illinois 60208 , United States.
Northwestern University Atomic and Nanoscale Characterization Experimental (NUANCE) Center, Northwestern University , Evanston , Illinois 60208 , United States.
ACS Nano. 2018 Oct 23;12(10):10347-10354. doi: 10.1021/acsnano.8b05623. Epub 2018 Oct 8.
Two-dimensional (2D) hybrid organic-inorganic perovskites (HOIPs) are recent members of the 2D materials family with wide tunability, highly dynamic structural features, and excellent physical properties. Ultrathin 2D HOIPs and their heterostructures with other 2D materials have been exploited for study of physical phenomena and device applications. The in-plane mechanical properties of 2D ultrathin HOIPs are critical for understanding the coupling between mechanical and other physical fields and for integrated devices applications. Here we report the in-plane mechanical properties of ultrathin freestanding 2D lead iodide perovskite membranes and their dependence on the membrane thickness. The in-plane Young's moduli of 2D HOIPs are smaller than that of conventional covalently bonded 2D materials. As the thickness increases from monolayer to three-layer, both the Young's modulus and breaking strength decrease, while three-layer and four-layer 2D HOIPs have almost identical in-plane mechanical properties. These thickness-dependent mechanical properties can be attributed to interlayer slippage during deformation. Our results show that ultrathin 2D HOIPs exhibit outstanding breaking strength/Young's modulus ratio compared to many other widely used engineering materials and polymeric flexible substrates, which renders them suitable for application into flexible electronic devices.
二维（2D）有机-无机杂化钙钛矿（HOIPs）是二维材料家族中的新成员，具有广泛的可调性、高度动态的结构特征和优异的物理性能。超薄二维HOIPs及其与其他二维材料的异质结构已被用于物理现象研究和器件应用。二维超薄HOIPs的面内力学性能对于理解机械场与其他物理场之间的耦合以及集成器件应用至关重要。在此，我们报告了超薄独立二维碘化铅钙钛矿膜的面内力学性能及其对膜厚度的依赖性。二维HOIPs的面内杨氏模量小于传统共价键合二维材料的杨氏模量。随着厚度从单层增加到三层，杨氏模量和断裂强度均降低，而三层和四层二维HOIPs具有几乎相同的面内力学性能。这些与厚度相关的力学性能可归因于变形过程中的层间滑动。我们的结果表明，与许多其他广泛使用的工程材料和聚合物柔性基板相比，超薄二维HOIPs表现出出色的断裂强度/杨氏模量比，这使其适用于柔性电子器件。
