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%. Two-dimensional materials look poised to revolutionize information and communication technologies. Here, the authors leveraged spatially resolved ellipsometry to engineer the optical absorption of graphene on hexagonal boron nitride substrates, thereby disclosing effective solutions for flexible optoelectronics.