THz Plasmonics of Quasi-freestanding Bilayer Epitaxial Graphene via H-intercalation

Graphene plasmonics has attracted attention as a suitable platform for tunable THz optoelectronics. THz plasmonic resonances in conventional large-area graphene, however, suffer from low quality factor (Q) because of high carrier scattering rate. This low Q is attributed to charge carrier induced scattering and lower carrier mobility caused by the partially covalent bonding between the silicon carbide (SiC) substrate and the 6$\surd $3 buffer layer between the substrate and EG. Improving the Q of plasmons makes stronger THz resonance effects and also enable THz optoelectronics with fine tunability in frequency via gating. EG on Si-face, semi-insulating 6H-SiC was intercalated in-situ by hydrogen (H$_{\mathrm{2}})$, releasing the buffer layer from SiC forming quasi-freestanding bilayer graphene. H-intercalation time was varied from 0 -- 75 minutes and structural, electrical and optical properties were explored, revealing at long H-intercalation durations high carrier mobility (3000-4000 cm$^{\mathrm{2}}$/Vs) and high sheet carrier concentration (1E13 cm$^{\mathrm{-2}})$ independent of carrier mobility. Far IR simultaneous transmission/reflection measurements revealed a narrow frequency response with line widths ($\gamma )$ smaller in H-intercalated EG (30cm$^{\mathrm{-1}})$ than observed in pristine EG (\textgreater 100cm$^{\mathrm{-1}})$ consistent with the improved mobility.