Isolation and characterization of atomically thin mica phyllosilicates

TL;DR

This study explores the potential of earth-abundant mica minerals as high-quality, atomically thin insulators for 2D electronic devices, providing detailed characterization and a catalog of their optical properties.

Contribution

It presents the first detailed characterization and classification of exfoliated biotite and muscovite flakes, highlighting their suitability as scalable insulators in 2D device applications.

Findings

Classified exfoliated mica flakes into three types using EDX spectroscopy

Provided a catalog of RGB contrast values for flakes from bilayer to 175 nm

Reported the complex index of refraction for the investigated mica materials

Abstract

One of the roadblocks to employing two-dimensional (2D) materials in next generation devices is the lack of high quality insulators. Insulating layered materials with inert and atomically flat surfaces are ideal for high performance transistors and this has been exemplified with commonly used boron nitride. While the list of insulating 2D materials is limited, the earth-abundant phyllosilicates are particularly attractive candidates. Here, we investigate the properties of atomically thin biotite and muscovite, the most common and commercially important micas from the rock-forming minerals. From a group of five natural bulk samples, energy dispersive X-ray spectroscopy is used to classify exfoliated flakes into three types of biotite, including the phlogopite endmember, and two muscovites. We provide a catalog of RGB contrast values for exfoliated flakes ranging from bilayer to approximately 175 nm. Additionally, we report the complex index of refraction for all investigated materials based on micro-reflectance measurements. Our findings suggest that earth-abundant phyllosilicates could serve as scalable insulators for logic devices employing 2D materials, potentially overcoming current limitations in the field.