Investigation of hybrid plasmons in a highly crystalline Bi₂Se₃/C₆₀ heterostructure using low-loss electron energy loss spectroscopy

Topological Insulators (TIs) present an interesting materials platform for nanoscale, high frequency devices because they support high mobility, low scattering electronic transport within confined surface states. However, a robust methodology to control the properties of surface plasmons in TIs has yet to be developed. Surface doping of TIs with molecules may provide tunable control of the two-dimensional plasmons in Bi₂Se₃, but exploration of such heterostructures is still at an early stage and usually confined to monolayers. We have grown heterostructures of Bi₂Se₃/C₆₀ with exceptional crystallinity. Electron energy loss spectroscopy (EELS) reveals significant hybridisation of π states at the interface, despite the expectation for only weak van der Waals interactions, including quenching of 2D plasmons. Momentum-resolved EELS measurements are used to probe the plasmon dispersion, with Density Functional Theory predictions providing an interpretation of results based on interfacial charge dipoles. This work provides growth methodology and characterization of highly crystalline TI/molecular interfaces that can be engineered for plasmonic applications in energy, communications and sensing. (Figure presented.)