Isolation and Characterization\nof Atomically Thin\nMica Phyllosilicates

One of the roadblocks to employing two-dimensional (2D)\nmaterials\nin next-generation devices is the lack of high-quality insulators.\nInsulating layered materials with inert and atomically flat surfaces\nare ideal for high performance transistors, and this has been exemplified\nwith commonly used boron nitride. While the list of insulating 2D\nmaterials is limited, the earth-abundant phyllosilicates are particularly\nattractive candidates. Here, we investigate the properties of atomically\nthin biotite and muscovite, the most common and commercially important\nmicas from the rock-forming minerals. From a group of five natural\nbulk samples, energy dispersive X-ray spectroscopy is used to classify\nexfoliated flakes into three types of biotite, including the phlogopite\nendmember and two muscovites. We provide a catalog of RGB contrast\nvalues for exfoliated flakes ranging from bilayer to approximately\n175 nm. Additionally, we report the complex index of refraction for\nall investigated materials based on microreflectance measurements.\nOur findings suggest that earth-abundant phyllosilicates could serve\nas scalable insulators for logic devices employing 2D materials, potentially\novercoming the current limitations in the field.