Dresden 2020 – scientific programme
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O: Fachverband Oberflächenphysik
O 27: Poster Session - Graphene: Electronic Structure, Excitations, etc.
O 27.2: Poster
Monday, March 16, 2020, 18:15–20:00, P1A
Spatial Variations in the Electronic Structure of Twisted Bilayer Graphene on HOPG — •Birce Sena Tömekce1, Dilek Yildiz1, 2, and Oguzhan Gürlü1 — 1Department of Physics, Istanbul Technical University, 34460, Istanbul, Turkey — 2Department of Physics, Harvard University, Cambridge, MA 02138, USA
Twist of a bilayer graphene generates moiré superlattices with a periodicity that depends on the twist angle. Such periodic pattern arises due to modulation of local density of states (LDOS) along the surface which can be detected by scanning tunneling microscopy (STM). It is known that the electronic properties of twisted bilayer graphene vary with the twist angle. Cyclohexane dropcasting on highly oriented pyrolytic graphite (HOPG) induces twist between graphene layers. Hence, we used this method to form moiré zones on HOPG. In this study, we investigated the electronic properties of moiré patterns with various periodicities and their boundaries on HOPG surface by STM and scanning tunneling spectroscopy (STS) together with lock-in technique. We studied spatial distribution of charge density of the surface by differential conductance (dI/dV) mapping. For most of the observed moiré patterns, charge density modulation tends to decrease and becomes homogenous with increasing magnitude of bias voltage, while moiré boundaries might show arbitrary changes. In addition, we obtained dI/dV spectra on different positions on moiré regions, their boundaries and HOPG surface adjacent to the moiré regions. In this presentation, we will report on bias dependent dI/dV maps and discuss conducting behaviors of the encountered moiré zones.