Correlation between the optical absorption and twisted angle of bilayer graphene observed by high-resolution reflectance confocal laser microscopy

We report a systematic study of the optical absorption of twisted bilayer graphene (tBLG) across a large range of twist angles from 0 degrees to 30 degrees using a high-resolution reflectance confocal laser microscopy (RCLM) system. The high-quality single crystalline tBLG was synthesized via the efficient plasma enhanced chemical vapor deposition techniques without the need of active heating. The sensitivity of acquired images from the RCLM were better than conventional optical microscopes. Although the highest spatial resolution of RCLM is still lower than scanning electron microscopes, it possesses the advantages of beam-damage and vacuum free. Moreover, the high intensity-resolution (sensitivity) images firstly allowed us to distinguish the slight absorption differences and analyze the correlation between the optical absorption and twisted angle of tBLG after data processing procedures. A maximum absorption (minimum transmission) was observed at the stacking angle of tBLG from 10 degrees to 20 degrees, indicating the interplay between the laser and the electron/hole van-Hove singularities when tBLG oriented around the critical angle (theta(c)similar to 13 degrees). The twisted angle correlated optical absorption paves an alternative way not only to visibly identify the interlayer orientation of tBLG but also to reflect the characterization of the interlayer coupling via its band structure. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

A systematic study of the optical absorption of twisted bilayer graphene (tBLG) was conducted using high-resolution reflectance confocal laser microscopy (RCLM), revealing maximum absorption at stacking angles of 10 to 20 degrees. The research provides valuable insights into interlayer orientation of tBLG.