title: Boron nitride-graphene nanocapacitor and the origins of anomalous size-dependent increase of capacitance.
abstract: Conventional wisdom suggests that decreasing dimensions of dielectric materials (e.g., thickness of a film) should yield increasing capacitance. However, the quantum capacitance and the so-called "dead-layer" effect often conspire to decrease the capacitance of extremely small nanostructures, which is in sharp contrast to what is expected from classical electrostatics. Very recently, first-principles studies have predicted that a nanocapacitor made of graphene and hexagonal boron nitride (h-BN) films can achieve superior capacitor properties. In this work, we fabricate the thinnest possible nanocapacitor system, essentially consisting of only monolayer materials: h-BN with graphene electrodes. We experimentally demonstrate an increase of the h-BN films' permittivity in different stack structures combined with graphene. We find a significant increase in capacitance below a thickness of ∼5 nm, more than 100% of what is predicted by classical electrostatics. Detailed quantum mechanical calculations suggest that this anomalous increase in capacitance is due to the negative quantum capacitance that this particular materials system exhibits.
authors.affiliation: Department of Materials Science and NanoEngineering, Rice University , Houston, Texas 77005, United States.
authors.forename: Gang
authors.initials: G
authors.lastname: Shi
authors.forename: Yuranan
authors.initials: Y
authors.lastname: Hanlumyuang
authors.forename: Zheng
authors.initials: Z
authors.lastname: Liu
authors.forename: Yongji
authors.initials: Y
authors.lastname: Gong
authors.forename: Weilu
authors.initials: W
authors.lastname: Gao
authors.forename: Bo
authors.initials: B
authors.lastname: Li
authors.forename: Junichiro
authors.initials: J
authors.lastname: Kono
authors.forename: Jun
authors.initials: J
authors.lastname: Lou
authors.forename: Robert
authors.initials: R
authors.lastname: Vajtai
authors.forename: Pradeep
authors.initials: P
authors.lastname: Sharma
authors.forename: Pulickel M
authors.initials: PM
authors.lastname: Ajayan