Grammaticalized Sentence Ender -KEY.

Ph.D. Thesis. University of Hawaiʻi at Mānoa 2018

Highly-stretchable and water impermeable thermally-grown silicon dioxide thin film with wavy structures

To ensure chemical stability and long-term operation, organic electronic devices require encapsulation layer with low water vapor transmittance rate because organic components in organic electronic device are vulnerable to humidity. Encapsulation of commercialized OLEDs are rigid glass and epoxy resin, which are not suitable for flexible devices requiring high flexibility. TFE (thin-film encapsulation) technique has been studied for flexible device encapsulation. Amorphous materials are selected for TFE materials because they are dense and transparent and do not have fast diffusion paths like grain boundary. Thermally-grown silicon dioxide, oxidized from single crystal silicon substrate at high temperature, has ultra-low water vapor transmittance rate due to high density without pinholes and defects. However, the thermally-grown silicon dioxide thin films have a low elastic limit (\u3c 1%) and show brittle fracture alike typical amorphous materials. For that reasons, it is necessary to improve the mechanical properties of the thermally-grown silicon dioxide thin film for flexible encapsulation. In this study, we tried to improve the stretchability by applying the wavy structure to thermally-grown silicon dioxide and developed the wavy structure texturing of single crystal silicon substrate by using photo-lithography and various etching process. we fabricated a highly-stretchable wavy thermally-grown silicon dioxide TFE by oxidizing wavy textured crystalline silicon substrate. Also, we carried out cyclic tensile test of submicron scale wavy thermally-grown silicon dioxide films and defined the elastic limit, and the stretchability. And then, we analyze the enhancement of stretchability by finite element analysis on the wavy and flat thermally-grown silicon dioxide TFE and discussed about the correlation between the improvement of stretchability and wavy structure

Quantum simulator for the Hubbard model with long-range Coulomb interactions using surface acoustic waves

A practical experimental scheme for a quantum simulator of strongly correlated electrons is proposed. Our scheme employs electrons confined in a two dimensional electron gas in a GaAs/AlGaAs heterojunction. Two surface acoustic waves are then induced in the GaAs substrate, which create a two dimensional ``egg-carton'' potential. The dynamics of the electrons in this potential is described by a Hubbard model with long-range Coulomb interactions. The state of the electrons in this system can be probed via its conductance and noise properties. This allows the identification of a metallic or insulating state. Numerical estimates for the parameters appearing in the effective Hubbard model are calculated using the proposed experimental system. These calculations suggest that observations of quantum phase transition phenomena of the electrons in the potential array are within experimental reach.Comment: 5 pages, 5 figure

Tomonaga-Luttinger liquid correlations and Fabry-Perot interference in conductance and finite-frequency shot noise in a single-walled carbon nanotube

We present a detailed theoretical investigation of transport through a single-walled carbon nanotube (SWNT) in good contact to metal leads where weak backscattering at the interfaces between SWNT and source and drain reservoirs gives rise to electronic Fabry-Perot (FP) oscillations in conductance and shot noise. We include the electron-electron interaction and the finite length of the SWNT within the inhomogeneous Tomonaga-Luttinger liquid (TLL) model and treat the non-equilibrium effects due to an applied bias voltage within the Keldysh approach. In low-frequency transport properties, the TLL effect is apparent mainly via power-law characteristics as a function of bias voltage or temperature at energy scales above the finite level spacing of the SWNT. The FP-frequency is dominated by the non-interacting spin mode velocity due to two degenerate subbands rather than the interacting charge velocity. At higher frequencies, the excess noise is shown to be capable of resolving the splintering of the transported electrons arising from the mismatch of the TLL-parameter at the interface between metal reservoirs and SWNT. This dynamics leads to a periodic shot noise suppression as a function of frequency and with a period that is determined solely by the charge velocity. At large bias voltages, these oscillations are dominant over the ordinary FP-oscillations caused by two weak backscatterers. This makes shot noise an invaluable tool to distinguish the two mode velocities in the SWNT.Comment: 20 pages, 9 figure

Stochastic Formation of Polariton Condensates in Two Degenerate Orbital States

We explore the exciton-polariton condensation in the two degenerate orbital states. In the honeycomb lattice potential, at the third band we have two degenerate vortex-antivortex lattice states at the inequivalent K and K'-points. We have observed energetically degenerate condensates within the linewidth ~ 0.3 meV, and directly measured the vortex-antivortex lattice phase order of the order parameter. We have also observed the intensity anticorrelation between polariton condensates at the K- and K'-points. We relate this intensity anticorrelation to the dynamical feature of polariton condensates induced by the stochastic relaxation from the common particle reservoir.Comment: 5 pages, 4 figure