Ultrafast carrier cooling in bilayer graphene with intercalated hydrogen atoms

We report on energy relaxation dynamics in epitaxially grown quasi-free-standing bilayer graphene on SiC substrate utilizing THz pump-probe spectroscopy. Hydrogen atom intercalation (HI) between the graphene and substrate is introduced to study graphene-substrate coupling on the energy relaxation process. Recently, interlayer energy transfer mechanisms are observed through carrier relaxation time measurements. We investigate a distinct current-heating mechanism to establish the role of HI on the carrier energy relaxation. Increased relaxation times for H intercalated substrates has been attributed to reduced coupling between the graphene and the substrate. In our samples, control of the density of partial intercalation of H atoms is carried out during the growth process; we will report on the energy flow rate for fully and partially intercalated graphene. We record the energy relaxation via THz spectroscopy post photoexcitation of graphene. Moreover, changes in THz conductivity have been measured. Experimental data do not reflect remarkable variations in THz conductivity as a function of excitation wavelength between 1.7um – 4.3um. These measurements were performed using quasi-free-bilayer graphene on SiC. The role of intercalation of hydrogen is undergoing further investigation.