Anomalous optical response of graphene on hexagonal boron nitride substrates

Graphene/ h BN heterostructures can be considered as one of the basic building blocks for the next-generation optoelectronics mostly owing to the record-high electron mobilities. However, currently, the studies of the intrinsic optical properties of graphene are limited to the standard substrates (SiO 2 /Si, glass, quartz) despite the growing interest in graphene/ h BN heterostructures. This can be attributed to a challenging task of the determination of h BN’s strongly anisotropic dielectric tensor in the total optical response. In this study, we overcome this issue through imaging spectroscopic ellipsometry utilizing simultaneous analysis of h BN’s optical response with and without graphene monolayers. Our technique allowed us to retrieve the optical constants of graphene from graphene/ h BN heterostructures in a broad spectral range of 250–950 nm. Our results suggest that graphene’s absorption on h BN may exceed the one of graphene on SiO 2 /Si by about 60%.