ALD based Metal-insulator-metal (MIM) Nanocapacitors for Energy Storage

Abstract

In this paper, we demonstrate the feasibility of using metal-insulator-metal (MIM) capacitors for energy storage. Using an all-ALD approach we deposit TiN, Al2O3 and TiN as the three constitutive films for the MIM stack, inside high aspect ratio (upto 200:1), self assembled, nanoporous anodic aluminum oxide (AAO) templates. A 10µm deep porous template yields a planar capacitance density of ~100µF/cm2. The high capacitance values ensure the energy densities in these capacitors approach values close to electrochemical capacitors. Furthermore, the fast charge-discharge rates due to the electrostatic nature of these capacitors ensure that we achieve these energy densities without sacrificing high power densities. The MIM capacitors therefore have the potential to contribute to a broad range of electrical energy storage applications requiring high energy and power.