Corrugated epitaxial graphene/SiC interfaces: photon excitation and probing
Localized energy exchange and mechanical coupling across a few nm gap at a corrugated graphene–substrate interface remain great challenges to study. In this work, an infrared laser is used to excite an unconstrained epitaxial graphene/SiC interface to induce a local thermal non-equilibrium. The interface behavior is uncovered using a second laser beam for Raman excitation. Using Raman peaks for dual thermal probing, the temperature difference across a gap of just a few nm is determined precisely. The interfacial thermal conductance is found to be extremely low: 410 ± 7 W m−2 K−1, indicating poor phonon transport across the interface. By decoupling of the graphene's mechanical and thermal behavior from the Raman wavenumber, the stress in graphene is found to be extremely low, uncovering its flexible mechanical behavior. Based on interface-enhanced Raman, it is found that the increment of interface separation between graphene and SiC can be as large as 2.9 nm when the local thermal equilibrium is destroyed.