Theory of Phonon Thermal Transport in Graphene and Graphite
Alofi, Ayman Salman Shadid
Thesis or dissertation
University of Exeter
Reason for embargo
I intend to publish some research papers.
Thermal properties of graphene and graphite have been investigated by employing the analytical expressions for the phonon dispersion relations and the vibrational density of states derived by Nihira and Iwata, which are based on the semicontinuum model proposed by Komatsu and Nagamiya. The thermal conductivities of graphene and graphite are computed within the framework of Callaway’s effective relaxation time theory. The Normal-drift contribution (the correction term in Callaway’s theory) produces a significant addition to the result obtained from the single-mode relaxation time theory, clearly suggesting that the single-mode relaxation time approach alone is inadequate for describing the phonon conductivity of graphene. Its contribution to the thermal conductivity arises from the consideration of the momentum conserving nature of three-phonon Normal processes and is found to be very important for explaining the magnitude as well as the temperature dependence of the experimentally measured results for graphene and graphite. This model has not been implemented before for studying the thermal conductivity of graphene. Also the model has been applied to compute the thermal conductivity of graphene, graphite basal planes, and graphite c-axis. This has further been used to investigate the evolution of thermal properties from graphene to graphite as a function of layer thickness and temperature. The effects of isotopes and tensile strain on the graphene thermal properties have been examined within this model and compared with other available studies.
PhD in Physics