Graphene as a Spin-Polarized Tunnel Barrier

Authored by: Olaf M.J. van ’t Erve , Enrique Cobas , Adam L. Friedman , Connie H. Li , Aubrey T. Hanbicki , Jeremy T. Robinson , Berend T. Jonker

Graphene Science Handbook

Print publication date:  April  2016
Online publication date:  April  2016

Print ISBN: 9781466591356
eBook ISBN: 9781466591363
Adobe ISBN:

10.1201/b19460-3

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Abstract

This chapter describes a novel use of graphene as a tunnel barrier for both charge and spin transport. Graphene is typically studied for its extraordinary in-plane conductance properties, while its out-of-plane transport properties are largely ignored. Graphene is metallic in-plane due the large availability of conduction channels. In contrast, there are substantially fewer out-of-plane conduction channels, resulting in a low resistivity in that configuration. A tunnel barrier comprises of two electrodes separated by a thin insulator where current flows between the electrodes entirely by quantum mechanical tunneling. Graphene exhibits many of the characteristics expected for an ideal tunnel barrier. The strong in-plane sp2 bonding of carbon atoms results in a strong tendency to form complete, defect-free monolayers, enabling tunnel barriers with discrete thicknesses. Graphene is chemically inert and thus prevents the electrodes from intermixing with the tunnel barrier material and/or getting chemically altered. It is also impervious to diffusion, forming a natural diffusion barrier between the two electrodes. It is thermally robust, which allows for an increased thermal budget of the overall structure. As theory predicts, graphene can also be an excellent spin filter in combination with a few selected ferromagnetic contacts. This chapter summarizes the tunnel barrier properties of graphene and its potential use in spintronic devices.

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