Mapping of Bernal and non-Bernal stacking domains in bilayer graphene using infrared nanoscopy.

Bilayer graphene (BLG) shows great potential as a new material for opto-electronic devices because its bandgap can be controlled by varying the stacking orders, as well as by applying an external electric field. An imaging technique that can visualize and characterize various stacking domains in BLG may greatly help in fully utilizing such properties of BLG. Here we demonstrate that infrared (IR) scattering-type scanning near-field optical microscopy (sSNOM) can visualize Bernal and non-Bernal stacking domains of BLG, based on the stacking-specific inter- and intra-band optical conductivities. The method enables nanometric mapping of stacking domains in BLG on dielectric substrates, augmenting current limitations of Raman spectroscopy and electron microscopy techniques for the structural characterization of BLG.