Transport studies in graphene-based materials and structures

Hu, Jiuning Ph.D., Purdue University, May 2015. Transport studies in graphenebased materials and structures. Major Professor: Yong P. Chen. Graphene, a single atomic layer of graphite, has emerged as one of the most attractive materials in recent years for its many unique and excellent properties, inviting a broad area of fundamental studies and applications. In this thesis, we present some theoretical/experimental studies about the thermal, electronic and thermoelectric transport properties in graphene-based systems. We employ the molecular dynamic simulations to study the thermal transport in graphene nanoribbons (GNRs) exhibiting various properties, including chirality dependent thermal conductivity, thermal rectification in asymmetric GNRs, defects and isotopic engineering of the thermal conductivity and negative differential thermal conductance (NDTC) at large temperature biases. We prove a theorem on the existence of NDTC in general one-dimensional diffusive thermal transport. We synthesis graphene composites and characterize their electric and thermal properties. Their electrical conductivity follows the percolation theory. We use 3-w method to measure the thermal conductivity and find that their thermal conductivities can be tuned by the graphene filler concentration. We build a micro-manipulator to accurately align and transfer twodimensional materials, e.g., graphene and boron nitride (BN). We then fabricate the stacked BN/grapnene/BN/graphene/BN systems with isolated metal contacts to each graphene layer, to study the counterflow thermoelectric transport and Coulomb drag. In the last we present our theoretical considerations about the transport properties