Ultrafast hot-carrier cooling in quasi freestanding bilayer graphene with hydrogen intercalated atoms

Femtosecond-THz optical pump probe spectroscopy is employed to investigate the cooling dynamics of hot carriers in quasi-free standing bilayer epitaxial graphene with hydrogen interacalation. We observe longer decay time constants, in the range of 2.6 to 6.4 ps, compared to previous studies on monolayer graphene, which increase nonlinearly with excitation intensity. The increased relaxation times are due to the decoupling of the graphene layer from the SiC substrate after hydrogen intercalation which increases the distance between graphene and substrate. Furthermore, our measurements show that the supercollision mechanism is not related to the cooling process of the hot carriers, which is ultimately achieved by electron optical phonon scattering.

Automated summary

In this study, femtosecond-THz optical pump probe spectroscopy was used to investigate the cooling dynamics of hot carriers in quasi-free standing bilayer epitaxial graphene with hydrogen intercalation. We observed longer decay time constants, ranging from 2.6 to 6.4 ps, compared to previous studies on monolayer graphene, and these times increased non-linearly with excitation intensity. The increased relaxation times were attributed to the decoupling of the graphene layer from the SiC substrate after hydrogen intercalation, which increased the distance between graphene and substrate. Furthermore, our measurements showed that the supercollision mechanism was not related to the cooling process of hot carriers, which was primarily achieved through electron-optical phonon scattering.