Charge and heat transport through interfaces in hybrid nanostructures

This dissertation presents the experimental study of the effect of interfaces on charge and heat transport in hybrid nanostructures. First, experimental measurements of charge transport in metal-molecule-metal junctions, using thermopower are discussed. Thermopower measurements offer an alternative transport measurement that can characterize the dominant transport orbital and is independent of the number of molecules in the junction. Thermopower measurements of a series of substituted benzenedithiols and of benzenedicyanide, show that the chemistry of the molecule has a large affect on transport properties of the junction. Cyanide endgroups were found to radically change transport relative to benzenedithiol (where transport is dominated by the highest occupied molecular orbital) such that transport is dominated by the lowest unoccupied molecular orbital (LUMO) in BDCN, while substituents on BDT generated small and predictable changes in transmission.;Next transport variations in a series of thiol-bound aromatic junctions are quantified. For all molecules, these measurements imply fluctuations in the height of the molecular transmission barrier nearly as large as the barrier itself. The transport fluctuations, increase with the number of benzene rings, and are dominated by the junction-to-junction variations, which arise during the repeated forming and breaking of molecular junctions.;The effect of interfaces on thermal transport in nanostructured materials is discussed using experimental measurements of thermal conductivity on diamondoids. Diamondoid molecules are cage like saturated hydrocarbons and can be assumed as repeating units of the diamond lattice. The measured thermal conductivity of lower diamondoids, is much lower than the minimum predicted value, using the Einstein model. These materials could potentially be the first known materials whose thermal conductivities are much lower than the calculated lower limit of thermal conductivity.;Finally the development of fiber aligned thermal interrogation (FATI), a non-contact and inexpensive technique, to measure thermal conductivity of a large variety of samples is discussed. This technique can be used to measure the thermal conductivity of a wide variety of samples from bulk to thin films, which span 4 orders of magnitude from ∼ 0.1 W/m-K to ∼ 160 W/m-K.