Spintronics and thermoelectrics in exfoliated and epitaxial graphene

This thesis is about two subjects: graphene spintronics and graphene thermoelectrics. Spintronics is about the creation and manipulation of spin currents. These are electrical currents in which we can control the spin orientation (up or down) of the conduction electrons. The second subject, thermoelectrics, is about the interaction between heat and charge currents. A classic thermoelectric phenomena is the Peltier effect, the cooling or heating of an interface between two materials when an electric current is flowing through.

Graphene is an interesting material for studying both spintronic and thermoelectric effects. Spins in graphene can travel unperturbed over a distance of several micrometers at room temperature, further than in any other material. And the strength of the Peltier effect in graphene can be controlled with an applied voltage, even allowing for the switching between cooling and heating the interface.

In this thesis I investigate the suitability of epitaxial graphene in spintronic applications. Epitaxial graphene is a large area graphene type that can be grown on a silicon carbide (SiC) chip. I show that it is possible to produce wafer scale graphene spin devices and that spin transport behaves differently on this particular substrate, because spins are temporarily immobilized in charge traps that are present in the graphene-SiC interface.

I also investigate a nanodevice that (1) can switch between heating and cooling of a graphene-gold interface and (2) can measure the induced temperature change using a nano-scaled thermocouple.