Mechanistic Origin of the Ultrastrong Adhesion between Graphene and a-SiO2: Beyond van der Waals

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• 作者：Sandeep Kumar ; David Parks ; Ken Kamrin
• 刊名：ACS Nano
• 出版年：2016
• 出版时间：July 26, 2016
• 年：2016
• 卷：10
• 期：7
• 页码：6552-6562
• 全文大小：745K
• 年卷期：0
• ISSN：1936-086X

文摘

The origin of the ultrastrong adhesion between graphene and a-SiO₂ has remained a mystery. This adhesion is believed to be predominantly van der Waals (vdW) in nature. By rigorously analyzing recently reported blistering and nanoindentation experiments, we show that the ultrastrong adhesion between graphene and a-SiO₂ cannot be attributed to vdW forces alone. Our analyses show that the fracture toughness of the graphene/a-SiO₂ interface, when the interfacial adhesion is modeled with vdW forces alone, is anomalously weak compared to the measured values. The anomaly is related to an ultrasmall fracture process zone (FPZ): owing to the lack of a third dimension in graphene, the FPZ for the graphene/a-SiO₂ interface is extremely small, and the combination of predominantly tensile vdW forces, distributed over such a small area, is bound to result in a correspondingly small interfacial fracture toughness. Through multiscale modeling, combining the results of finite element analysis and molecular dynamics simulations, we show that the adhesion between graphene and a-SiO₂ involves two different kinds of interactions: one, a weak, long-range interaction arising from vdW adhesion and, second, discrete, short-range interactions originating from graphene clinging to the undercoordinated Si (≡Si·) and the nonbridging O (≡Si–O·) defects on a-SiO₂. A strong resistance to relative opening and sliding provided by the latter mechanism is identified as the operative mechanism responsible for the ultrastrong adhesion between graphene and a-SiO₂.