Engineering confined Electrons and Photons at the Nanoscale

The transport of electrons and photons can have surprising characteristics when confined to the nanometer scale. The electronic and optical density of states can be carefully controlled by engineering geometry and other degrees of freedom at small scales, and recent advances in microfabrication and chemistry have granted us unprecedented control over these parameters. The dissertation concerns the integration of nanostructures into photonic/plasmonic, electronic, and optoelectronic devices. First, we show that plasmonic devices integrating metallic and semiconducting nanowires and other nanostructures can be used to control light-matter interaction and to generate and manipulate light in an integrated fashion. Specifically, a novel plasmonic resonator composed of crystalline silver nanowires surrounded by patterned dielectric to define distributed Bragg reflectors is realized and coupled to quantum emitters to show Purcell enhancement of spontaneous emission. Furthermore, silver nanowire plasmon waveguides are interfaced to semiconductor nanowires to make a near-field optoplasmonic circuit, in which plasmons are generated and detected electrically. Both studies exploit the electric field confinement afforded by plasmonic nanostructures to achieve enhanced light-matter interaction. The next part of the dissertation demonstrates control over electron transport in a single molecule transistor in a regime where electrons tunnel one at a time, and are strongly influenced by molecular degrees of freedom. Finally, a nanowire-based photoelectrochemical cell is presented that exhibits water splitting with sunlight. By exploiting the unique optical and electronic properties of nanowire networks, we show that a network of titanium dioxide nanowires can be used as a photoanode to achieve record energy conversion efficiencies. These studies show the promise of engineering confined electrons and photons in nanostructures to applications in nanoelectronics, energy, optoelectronics, and quantum optics.