Tuning the electronic structure of graphene by controlling spatial confinement

Spatial confinement provides a direct route for reshaping the low-energy π bands of graphene-based materials. Here, we investigate few-layer graphene heterostructures in which one layer is replaced by a periodic array of armchair or zigzag graphene nanoribbons (AGNRs or ZGNRs). Using a six-parameter Slonczewski–Weiss–McClure tight-binding model, we show that the resulting band structures cannot, in general, be interpreted as a simple superposition of isolated graphene sheets and isolated nanoribbons. Instead, the electronic structure is controlled by the ribbon width, edge orientation, and whether the nanoribbon array is embedded between two graphene sheets or placed on top of a bilayer. Semiconducting AGNR arrays embedded in trilayer graphene leave graphene-like dispersive bands nearly intact for narrow ribbons but tune the band steepness for wider ribbons, whereas semimetallic AGNR arrays preserve a ribbon-derived low-energy channel and suppress the parabolic branch of pristine trilayer graphene. In bilayer graphene, a gapless AGNR array opens a local gap of approximately 0.6 eV at the folded Dirac point. These results identify spatial confinement and layer placement as simple design parameters for tuning graphene heterostructures without changing their chemical composition.