Sub-nanometer Atomic Layer Deposition for Spintronics in Magnetic Tunnel Junctions Based on Graphene Spin-Filtering Membranes

Abstract

We report on the successful integration of low-cost, conformal, and versatile atomic layer deposited (AID) dielectric in Ni-Al2O3-Co magnetic tunnel junctions (MTJs) where the Ni is coated with a spin filtering graphene membrane. The AID tunnel barriers, as thin as 0.6 nm, are grown layer-by-layer in a simple, low vacuum ozone-based process, which yields high-quality electron transport barriers as revealed by tunneling characterization. Even under these relaxed conditions, including air exposure of the interfaces, a significant tunnel magnetoresistance is measured highlighting the robustness of the process. The spin filtering effect of graphene is enhanced, leading to an almost fully inversed spin polarization for the Ni electrode of -42%. This unlocks the potential of AID for spintronics with conformal, layer-by-layer control of tunnel barriers in magnetic tunnel junctions toward low-cost fabrication and down scaling of tunnel resistances.