Twist-Dependent Raman and Electron Diffraction Correlations in Twisted Multilayer Graphene

Abstract

Twisted multilayer graphene (tMLG), in contrast to twisted bilayer graphene, offers a range of angular rotations for tuning the properties of the system. In this work, a turbostratic graphene system with a high degree of two-dimensional (2D) crystallinity is chosen to represent tMLG. We have investigated the distribution and population of twist angles from distributed sextets in electron diffraction (SAED) patterns with the collective Raman behavior at the same locations. A descriptor, termed the turbostratic factor, was calculated on the basis of angular spacings in SAEDs, to account for their distribution; the greater the spread, the higher the turbostratic factor. Raman spectra have revealed that the turbostratic factor remains low (∼0°) for a graphitic region with a low 2D to G intensity ratio (<i>I</i>_2D/<i>I</i>_G) and increases rapidly at higher <i>I</i>_2D/<i>I</i>_G values, saturating at 60° for highly turbostratic systems. Relating the intensities associated with the sextets and <i>I</i>_2D/<i>I</i>_G values, we found the maximum achievable value of <i>I</i>_2D/<i>I</i>_G to be 17.92.