Graphene Nanoribbon Dielectric Passivation Layers for Graphene Electronics

Charged-impurity scattering is a serious problem that hinders the electrical properties of graphene. Toward large-scale and/or flexible graphene-based electronics, there is a strong demand for a high-κ dielectric layer which reduces charged-impurity density and screens the impurity scattering that passivates the graphene. We herein demonstrate that the structurally precise and soluble graphene nanoribbons (GNRs) act as excellent dielectric passivation layers. The wide-gap GNRs, synthesized through annulative π-extension polymerization, were selectively and stably fixed onto graphene via a simple drop-casting method. The carrier mobility of ∼30 nm thick GNR-adlayer-deposited graphene was approximately twice that in its original state. Electrical transport and Raman spectroscopic measurements revealed that the deposition of the GNR dielectric passivation layers reduced the charge puddles. These results suggest that the GNR adlayers prevent graphene from the oxygen/water redox couple adsorption and lift the graphene up from the underlying SiO2 substrate via strong π–π and CH−π interactions. Additionally, the relatively high dielectric constant (∼5.2) of the GNRs contributes to the increased screening effect. All these effects lead to a reduced impurity scattering, which increases carrier mobility.