New Method to Detect the Transport Scattering Mechanisms of Graphene Carriers

Detecting the carrier scattering mechanisms in a materials system is important for transport related science and engineering. The approaches of fast laser process and electrical conductivity matching were used in previous literature, which do not give accurate information on scattering relaxation time as a function of carrier energy for intrinsic photon-free transport. Graphene is considered as a model system in materials science studying for its simple atomic and electronic structures. Here we have developed a new methodology to detect the scattering relaxation time as a function of carrier energy, which can be used to infer the carrier scattering mechanisms at different temperatures. Our method utilizes the measured values of optimal Seebeck coefficient, for both P-type and N-type materials. This new approach can eliminate the influence from photon-carrier scattering in the fast-laser method, and avoid the over-fitting issue in the electrical conductivity matching method. We have then applied the new approach in the SiO2 substrated graphene system, and discovered that the Dirac carriers are mainly scattered by short-range interactions at 40 K. The scatter strength of long-range Coulomb interaction increases with temperature. At 300 K, the long-range and short-range interactions scatter the Dirac carriers with almost comparable strengths.