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Conventionalwisdom suggests that decreasing dimensions of dielectricmaterials (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 smallnanostructures, which is in sharp contrast to what is expected fromclassical electrostatics. Very recently, first-principles studieshave predicted that a nanocapacitor made of graphene and hexagonalboron 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 grapheneelectrodes. We experimentally demonstrate an increase of the h-BNfilms’ permittivity in different stack structures combinedwith graphene. We find a significant increase in capacitance belowa thickness of ∼5 nm, more than 100% of what is predicted byclassical electrostatics. Detailed quantum mechanical calculationssuggest that this anomalous increase in capacitance is due to thenegative quantum capacitance that this particular materials systemexhibits. [ABSTRACT FROM AUTHOR]

Strong in-plane bonding and weak van der Waals interplanarinteractionscharacterize a large number of layered materials, as epitomized bygraphite. The advent of graphene (G), individual layers from graphite,and atomic layers isolated from a few other van der Waals bonded layeredcompounds has enabled the ability to pick, place, and stack atomiclayers of arbitrary compositions and build unique layered materials,which would be otherwise impossible to synthesize via other knowntechniques. Here we demonstrate this concept for solids consistingof randomly stacked layers of graphene and hexagonal boron nitride(h-BN). Dispersions of exfoliated h-BN layers and graphene have beenprepared by liquid phase exfoliation methods and mixed, in variousconcentrations, to create artificially stacked h-BN/G solids. Thesevan der Waals stacked hybrid solid materials show interesting electrical,mechanical, and optical properties distinctly different from theirstarting parent layers. From extensive first principle calculationswe identify (i) a novel approach to control the dipole at the h-BN/Ginterface by properly sandwiching or sliding layers of h-BN and graphene,and (ii) a way to inject carriers in graphene upon UV excitationsof the Frenkell-like excitons of the h-BN layer(s). Our combined approachcould be used to create artificial materials, made predominantly frominter planar van der Waals stacking of robust bond saturated atomiclayers of different solids with vastly different properties. [ABSTRACT FROM AUTHOR]