The limits of Near Field Immersion Microwave Microscopy evaluated by imaging bilayer graphene Moir\'{e} patterns

TL;DR

This paper demonstrates that near-field microwave microscopy can achieve nanometer-scale resolution, down to 1 nm, by employing liquid immersion techniques and precise force control, using twisted bilayer graphene as a test sample.

Contribution

It introduces a novel approach combining microwave microscopy with liquid immersion and force control to surpass traditional resolution limits in nanoscale imaging.

Findings

Achieved 1 nm resolution in microwave imaging of bilayer graphene.

Demonstrated the effectiveness of liquid immersion and force control in enhancing resolution.

Validated the method on Moiré patterns in twisted bilayer graphene.

Abstract

Molecular and atomic imaging required the development of electron and scanning probe microscopies to surpass the physical limits dictated by diffraction. Nano-infrared experiments and pico-cavity tip-enhanced Raman spectroscopy imaging later demonstrated that radiation in the visible range can surpass this limit by using scanning probe tips to access the near-field regime. Here we show that ultimate resolution can be obtained by using scanning microwave imaging microscopy to reveal structures with feature sizes down to 1~nm using a radiation of 0.1~m in wavelength. As a test material we use twisted bilayer graphene, which is not only a very important recent topic due to the discovery of correlated electron effects such as superconductivity, but also because it provides a sample where we can systematically tune a superstructure Moir\'e patterns modulation from below one up to tens of nanometers. By analyzing the tip-sample distance dynamics, we demonstrate that this ultimate 10$^8$ probe-to-pattern resolution can be achieved by using liquid immersion microscopy concepts and exquisite force control exerted on nanoscale water menisci.