The limits of near field immersion microwave microscopy evaluated by imaging bilayer graphene moiré patterns

Abstract

Near field scanning Microwave Impedance Microscopy can resolve structures as small as 1 nm using radiation with wavelengths of 0.1 m. Combining liquid immersion microscopy concepts with exquisite force control exerted on nanoscale water menisci, concentration of electromagnetic fields in nanometer-size regions was achieved. As a test material we use twisted bilayer graphene, because it provides a sample where the modulation of the moiré superstructure pattern can be systematically tuned from Ångstroms up to tens of nanometers. Here we demonstrate that a probe-to-pattern resolution of 10⁸ can be obtained by analyzing and adjusting the tip-sample distance influence on the dynamics of water meniscus formation and stability.

Here, the authors image twisted bilayer graphene using scanning microwave imaging microscopy, revealing structures with sizes down to 1 nm. They show that is possible by using spontaneously forming nanoscale water menisci that concentrates the microwave fields in small regions.