Observation of the Intrinsic Bandgap Behavior in As-Grown Epitaxial Twisted Graphene (Postprint).

摘要

Twisted graphene is of particular interest due to several intriguing characteristics, such as its the Fermi velocity, van Hove singularities and electronic localization. Theoretical studies recently suggested the possible bandgap opening and tuning. Here, we report a novel approach to producing epitaxial twisted graphene on SiC (0001) and the observation of its intrinsic bandgap behaviour. The direct deposition of C60 on pre-grown graphene layers results in few-layer twisted graphene confirmed by angular resolved photoemission spectroscopy and Raman analysis. The strong enhanced G band in Raman and sp3 bonding characteristic in X-ray photoemission spectroscopy suggests the existence of interlayer interaction between adjacent graphene layers. The interlayer spacing between grapheme layers measured by transmission electron microscopy is 0.352 + or - 0.012 nm. Thermal activation behaviour and nonlinear current-voltage characteristics conclude that an intrinsic bandgap is opened in twisted graphene. Low sheet resistance (approximately 160 ohm square(exp1) at 10 K) and high mobility (approximately 2,000 cm(exp2)V 1s(exp1)1at 10 K) are observed.