Figure 2: STM topography and STS near zigzag and armchair edges.
From: Energy Bandgap and Edge States in an Epitaxially Grown Graphene/h-BN Heterostructure
(a) Three different energy bandgaps in a graphene layer epitaxially grown on h-BN/Cu(111) are illustrated as bulk bandgap, zigzag edge gaps, and armchair edge resonance. B stands for the bulk, ZZ for zigzag, and AC for armchair. (b) A (6.1 × 6.1) nm2 STM topography near a zigzag edge obtained with Vs = 0.1 V, and It = 15 nA. In the magnified inset image, bright spots at the center of the honeycomb lattice are visible in the 3D representation of a close-up view of this zigzag edge. Blue arrows indicate hollow sites in moiré patterns. (c) STM topography near an armchair edge of a (3.5 × 3.5) nm2 graphene layer obtained with Vs = 0.01V, and It = 15 nA. (d) Scanning tunneling spectra at five lattice constants away from a zigzag edge (full green circles), 2.4 nm away from the zigzag edge (full dark-red circles). Those at an armchair edge (full blue circles), five lattice constants away from the armchair edge (full black circles), five lattice constants away from another armchair edge (full red circles: the location is not shown in Fig. 2c). An inset spectrum indicates a spectrum after subtracting a linear Dirac dispersion and a parabolic tunneling background in a tip-sample geometry. The estimated errors of energy are ± 0.02 eV.
