Graphene heterostructures for spin and charge transport

A single atom thick layer of graphite is known as graphene. Despite its simplicity, graphene has made a major impact in research after being demonstrated to exist in 2004. Not only is it easy to make, using graphite, tape and a substrate, it also has remarkable electronic properties. But because graphene is basically a large surface, it is easily influenced by external factors. To improve the electronic quality of a graphene layer, it can be shielded from the environment using a thin layer of hexagonal boron nitride (h-BN). Stacking graphene and h-BN is however not trivial. Here we developed two methods to create such heterostructures. A straightforward way is to first deposit graphene on a sacrificial polymer layer and then release it on a h-BN crystal. A cleaner approach is by picking up crystal flakes one by one using a polymer coated stamp and depositing the resulting stack on a substrate. Using these methods, we create high quality graphene heterostructures, as is demonstrated by increased electron mobilities.Furthermore, we investigate graphene spin transport in heterostructure devices. Here the electron spin is used instead of charge to carry information. Graphene shows great potential due to its ability to carry spin information over record distances at room temperature. We find that in heterostructures spins can travel even further. Additionally, we exposed few layer graphene to irradiation and observe that spin transport properties are surprisingly robust despite the damage, further demonstrating the potential of graphene for spintronic applications