Passivation of Bi2Te3 topological insulator by transferred CVD-graphene : toward intermixing-free interfaces

The investigation, and ultimate application, of topological insulators, typically involve exposure to ambient conditions or their integration with metals, which lead to surface oxidation or material intermixing. X-ray photoelectron spectroscopy (XPS) measurements that demonstrate passivated and intermixing-free interfaces in the topological insulator BiTe by means of dry-transferred CVD graphene are reported. After air exposure, no traces of BiTe oxidation are found. Furthermore, it is demonstrated that graphene acts as a very efficient metal and chalcogen diffusion barrier in BiTe/graphene/permalloy (Py) heterostructures, which are relevant for spintronics. Such results are in stark contrast with the significant surface degradation observed in bare BiTe under ambient conditions and the deep Bi-Te bonding disruption that occurs in BiTe/Py heterostructures. These findings provide a new approach to control and engineer topological insulator interfaces for spintronic applications and a new platform to investigate the combined use of graphene and topological insulator Dirac states.