Nanoscale Infrared and Microwave Imaging of Stacking Faults in Multilayer Graphene.

Graphite exhibits a range of metastable stacking orders, with the number of possible configurations increasing exponentially with the number of layers. Most experimental studies have focused on Bernal and rhombohedral stacking due to the difficulty of identifying and isolating intermediate stacking orders. Motivated by this challenge, we present two atomic force microscopy (AFM) techniques that unambiguously distinguish stacking orders and defects in graphite flakes. Photothermal infrared AFM provides absolute contrast through IR spectral analysis across multiple wavelengths, while scanning microwave impedance microscopy reveals relative contrast among Bernal, intermediate, and rhombohedral domains. We demonstrate that both techniques provide high-contrast identification of stacking orders, are compatible with subsurface imaging through a hexagonal boron nitride dielectric layer, and can resolve nanoscale domain walls. These results pave the way for reliable fabrication of multilayer graphene devices with a well-defined interlayer registry.