Edge-Dependent Capacitive Response and Geometry-Tunable Metallization Field in Same-Lattice Graphene/Graphane/Graphene Nanoribbon Nanocapacitors

Abstract Using first-principles density functional theory calculations, this study investigates how crystallographic edge geometry and independently varied graphene-segment and graphane-spacer widths govern the field-induced response of same-lattice graphene/graphane/graphene nanoribbon nanocapacitors. Patterned hydrogenation creates laterally integrated, electronically distinct regions within a common carbon framework. Both zigzag and armchair architectures are semiconducting at zero field and exhibit interface-localized charge redistribution. Under sufficiently strong in-plane electric fields, the graphene segments become metallic and electrode-like, while the hydrogenated spacer retains its predominantly wide-gap insulating character and carries negligible net field-induced excess charge relative to the zero-field reference. The resulting regime shows nearly equal and opposite electrode charges, a finite potential drop across the spacer, and approximately linear charge–field and quadratic energy–field scaling. Increasing either lateral width generally lowers the metallization field in both edge geometries. Notably, fixed-graphene-width, variable-spacer-width calculations show that this reduction can occur even when the zero-field band gap remains nearly unchanged, demonstrating that the metallization field reflects the combined influence of the low-energy electronic structure and lateral electrostatic geometry rather than the zero-field band gap alone. At a common postclosure reference field, wider structures store more total charge and energy but exhibit lower gravimetric capacitance, revealing a trade-off between the field required to access the electrode-like regime and the mass-normalized capacitive response. Zigzag systems additionally undergo pronounced reconstruction of pre-existing edge magnetism, whereas armchair systems develop only weak spin polarization and generally higher gravimetric capacitance. These results identify edge geometry and both lateral widths as complementary design variables for controlling the metallization field and capacitive response.