Quasiparticle scattering induced by native defects in graphene devices

Atomic-scale defects in graphene-based heterostructures have been conjectured to have dramatic effects on their transport properties. To date however, no direct evidence for the presence of defects in graphene devices made from exfoliated graphite has been reported. We report scanning tunneling microscopy results which demonstrate for the first time the presence of native defects and their effect on the electronic properties of Bernal-stacked bilayer graphene devices. Quasiparticle interference measurements at various backgate voltages show a dependence of the scattering induced by the defects on the charge carrier concentration and type. We compare our experimental results to T-matrix-based simulations and discuss the various types of defects encountered in the devices. We also present results obtained on the graphite parent crystal which demonstrate the defects are already present in the parent crystal and are not created during the making of the device. We anticipate these results will have implications for various graphene-based devices, including magic-angle twisted bilayer graphene, for which atomic scale defects have been predicted to have considerable effects on the transport properties.