Competing scanning tunneling microscope tip-interlayer interactions for twisted multilayer graphene on the a-plane SiC surface

TL;DR

This study uses STM to image twisted multilayer graphene on SiC, revealing dynamic moiré patterns caused by tip-sample electrostatic interactions, and determines the twist angle between layers.

Contribution

First STM imaging of twisted multilayer graphene on SiC surface, identifying dynamic moiré patterns and their electrostatic origin.

Findings

Moiré patterns shift over 1 nm, observable with STM.

Twist angle between layers is 5.4 degrees.

Dynamic behavior involves continuous pattern shuffling.

Abstract

Scanning tunneling microscopy (STM) images are obtained for the first time on few layer and twisted multilayer epitaxial graphene states synthesized on n+ 6H-SiC a-plane non-polar surface. The twisted graphene is determined to have a rotation angle of 5.4{\deg} between the top two layers, by comparing moir\'e patterns from stick and ball models of bilayer graphene to experimentally obtained images. Furthermore, the experimental moir\'e pattern shows dynamic behavior, continuously shuffling between two stable surface arrangements one bond length apart. The moir\'e pattern shifts by more than 1 nm, making it easy to observe with STM. Explanation of this dynamic behavior is attributed to electrostatic interactions between the STM tip and the graphene sample.