Landscape of Charge Puddles in Graphene Nanoribbons on Hexagonal Boron Nitride

Recently, graphene nanoribbons (GNRs) on hexagonal boron nitride (h‐BN) substrates have been studied to develop high‐mobility devices or devices based on a 1D Moiré superlattice. For this purpose, a device‐level understanding of the charge‐puddle landscape of a GNR/h‐BN structure is needed when the charge puddles function as scattering sources for mobile charge carriers. Here, a puddle landscape is constructed on the basis of an analysis of the temperature dependencies of the conductance of GNR/h‐BN devices at various gate‐voltage values. For low‐, intermediate‐, and high‐temperature regions near the charge‐neutral point (CNP), the puddle size (50–200 nm), distance between neighboring puddles (40–170 nm), and potential depth of the puddles (in a range of 10 meV) in ∼100 nm wide GNR/h‐BN devices are obtained on the basis of Coulomb blockade, 1D variable‐range hopping, and thermally activated hopping, respectively. Based on the constructed puddle landscape, it is also concluded that the confinement‐gap energy for an ∼100 nm wide GNR is similar to that of the thermal activation energy near the CNP in the GNRs. The constructed puddle landscape for GNR/h‐BN devices is consistent with that obtained from scanning tunneling microscopy observations of graphene on an h‐BN structure. The puddle landscape of 100 nm wide graphene nanoribbons on hexagonal boron nitride (h‐BN) is constructed by analyzing the temperature dependence of the conductance at various gate‐voltage values, i.e., puddle size (a) 50–200 nm, distance between puddles (r) 40–170 nm, the potential depth of the puddles ≥10 meV, and confinement‐gap energy (Econ) ≤ 10 meV.