Enhancement of spin relaxation time in hydrogenated graphene spin valve devices

TL;DR

This study demonstrates that plasma hydrogenation of graphene significantly increases spin relaxation time, enhancing spin transport properties and enabling longer-distance spin detection at room temperature.

Contribution

It reports the first observation of up to three-fold increase in spin relaxation time in hydrogenated graphene, revealing a new method to control spin dynamics.

Findings

Spin relaxation time increased up to 2.7 ns after hydrogenation

Spin relaxation length remained nearly unchanged at 7 microns

Hydrogenation enabled spin detection over 11 microns

Abstract

Hydrogen adsorbates in graphene are interesting as they are not only strong Coulomb scatterers but they also induce a change in orbital hybridization of the carbon network from sp^2 into sp^3. This change increases the spin-orbit coupling and is expected to largely modify spin relaxation. In this work we report the change in spin transport properties of graphene due to plasma hydrogenation. We observe an up to three-fold increase of spin relaxation time tau_S after moderate hydrogen exposure. This increase of tau_S is accompanied by the decrease of charge and spin diffusion coefficients, resulting in a minor change in spin relaxation length lambda_S. At high carrier density we obtain lambda_S of 7 microns, which allows for spin detection over a distance of 11 microns. After hydrogenation a value of tau_S as high as 2.7 ns is measured at room temperature.