Electronic and Plasmonic Properties of Nano-Sized Gold/Strontium Titanate Interface
scanning probe microscopy
Mechanics of Materials
In this thesis, nano-sized metal/oxide interfaces are fabricated to determine the size dependence of electronic and resistive switching properties, effect of atomic structure on the orientation dependence of electronic properties, and mechanisms of plasmon-induced current enhancement. A combination of drop-casting and high temperature annealing enables orientation control over nano-sized metal/oxide interfaces. To examine the electronic properties, individual Au nanoparticle/SrTiO3 interfaces with sizes ranging from 20 to 150 nm are characterized via conductive atomic force microscopy, for two distinct interface orientations. Current-voltage characterization enables the determination of dominant electron transport mechanisms. The development of a depletion region results in the transition of electron transport mechanism from edge-effect-induced tunneling to inhomogeneity-induced statistical variations, as the interface decreases below a critical size. The resultant size-dependent Schottky properties dictate the size dependence of interface-controlled resistive switching behaviors, in addition to geometrical scaling of resistance. The effect of atomic structure on electronic properties is also investigated, via correlation of atomic structure characterized by high resolution transmission electron microscopy, electronic structure probed by electron energy loss spectroscopy, and measured electronic properties. The observed orientation dependence of reverse tunneling is attributed to interface defects induced by different atomic structures. Nanofabrication procedures are optimized to develop Au nano-antenna arrays on SrTiO3 substrate, to determine the photocurrent dependence on illumination condition and mechanisms of hot electron effect. Device design is assisted by finite-difference time-domain simulation of optical properties, targeted at near-infrared working range. Plasmon resonance frequency and intensity are demonstrated to be systematically tunable by varying device geometry. Photocurrent enhancement occurs around the resonance frequency, resulting from amplified absorption of plasmon resonance. Finally, possible approaches are proposed to optimize quantum yield of plasmon-induced current enhancement.