Department of Mechanical Engineering, University of Colorado, Boulder, Colorado 80309, USA.
Nano Lett. 2013 May 8;13(5):2309-13. doi: 10.1021/nl401180t. Epub 2013 Apr 30.
We present a unique experimental configuration that allows us to determine the interfacial forces on nearly parallel plates made from the thinnest possible mechanical structures, single and few layer graphene membranes. Our approach consists of using a pressure difference across a graphene membrane to bring the membrane to within ~10-20 nm above a circular post covered with SiOx or Au until a critical point is reached whereby the membrane snaps into adhesive contact with the post. Continuous measurements of the deforming membrane with an AFM coupled with a theoretical model allow us to deduce the magnitude of the interfacial forces between graphene and SiOx and graphene and Au. The nature of the interfacial forces at ~10-20 nm separation is consistent with an inverse fourth power distance dependence, implying that the interfacial forces are dominated by van der Waals interactions. Furthermore, the strength of the interactions is found to increase linearly with the number of graphene layers. The experimental approach can be used to measure the strength of the interfacial forces for other atomically thin two-dimensional materials and help guide the development of nanomechanical devices such as switches, resonators, and sensors.
我们提出了一种独特的实验配置，使我们能够确定由尽可能薄的机械结构（单层和少数层石墨烯膜）制成的近平行板之间的界面力。我们的方法包括在石墨烯膜上施加压差，使膜在覆盖有 SiOx 或 Au 的圆形柱体上方约 10-20nm 处，直到达到临界点，此时膜与柱体突然发生粘附接触。通过与原子力显微镜（AFM）耦合的连续测量，我们可以用理论模型来推断石墨烯和 SiOx 以及石墨烯和 Au 之间的界面力的大小。在约 10-20nm 的分离距离处，界面力的性质与逆四次幂距离的依赖性一致，这意味着界面力主要由范德华相互作用主导。此外，还发现相互作用的强度随石墨烯层数的增加呈线性增加。该实验方法可用于测量其他原子级二维材料的界面力强度，并有助于指导纳米机械器件（如开关、谐振器和传感器）的开发。
