Visualizing subsurface defects in graphite by acoustic atomic force microscopy

We describe a versatile platform, which combines atomic force acoustic microscopy, ultrasonic atomic force microscopy and heterodyne force microscopy. The AFM system can enable in-situ switching among these operation modes flexibly and thus benefit the discrimination of differences in mechanical properties and buried subsurface nanostructures. We demonstrate the potential of this platform for visualizing the subsurface defects of graphite. Our results show that tiny topographic edges are enhanced in acoustic oscillation signals whilst embedded defects and inhomogeneous in mechanical properties are made clearly distinguishable. The possibility of detecting subsurface defects in few-layer graphene is further discussed with first-principles calculations. Microsc. Res. Tech. 80:66-74, 2017. © 2016 Wiley Periodicals, Inc.