Publications by authors named "Yoonkee Kim"

Silver nanowire (AgNW) networks have demonstrated high optical and electrical properties, even better than those of indium tin oxide thin films, and are expected to be a next-generation transparent conducting electrode (TCE). Enhanced electrical and optical properties are achieved when the diameter of the AgNWs in the network is fairly small, that is, typically less than 30 nm. However, when AgNWs with such small diameters are used in the network, stability issues arise.

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We propose a nanofabrication process to generate large-area arrays of noble metal nanoparticles on glass substrates via nanoimprinting and dewetting of metallic thin films. Glass templates were made via pattern transfer from a topographic Si mold to an inorganically cross-linked sol-gel (IGSG) resist on glass using a two-layer polydimethylsiloxane (PDMS) stamp followed by annealing, which turned the imprinted resist into pure silica. The transparent, topographic glass successfully templated the assembly of Au and Ag nanoparticle arrays via thin-film deposition and dewetting at elevated temperatures.

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The low-power potential of oven-controlled MEMS oscillators.

IEEE Trans Ultrason Ferroelectr Freq Control

April 2013

It is shown that oven-controlled micro electromechanical systems (MEMS) oscillators have the potential of attaining a higher frequency stability, with a lower power consumption, than temperature-compensated crystal oscillators (TCXOs) and the currently manufactured MEMS oscillators.

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Antifouling surface with both superhydrophobicity and oil-repellency has been fabricated on glass substrate by forming fractal microstructure(s). The fractal microstructure was constituted by transparent silica particles of 100 nm diameter and transparent zinc-oxide columns grown on silica particles by atmospheric pressure cold plasma deposition. The sample surface was coated with a chemically adsorbed monomolecular layer.

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When a doubly rotated resonator is operated in a liquid, the displacement of the surface is partly out of the plane of the plate of the resonator. The out-of-plane component of the displacement propagates a damped compressional wave into the liquid, and the in-plane component propagates a damped shear wave. In this paper, we report the measurements of the series resonant frequency and the motional arm resistance of doubly rotated quartz resonators (theta approximately 35 degrees and phi = 7 degrees) in liquids to compare with singly rotated AT-cut resonators (theta approximately 35 degrees and phi = 0 degrees).

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Amplitude-frequency effect of Y-cut langanite and langatate.

IEEE Trans Ultrason Ferroelectr Freq Control

December 2003

Amplitude-frequency effect of a Y-cut langanite (LGN) resonator and a Y-cut langatate (LGT) resonator were measured. The frequency shifts from the baseline frequency with 1 mA were measured as a function of drive currents up to 28 mA. High-drive current shifted the frequency, but it also heated the crystal locally, causing temperature-related frequency changes.

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Force-frequency effect of Y-cut langanite and Y-cut langatate.

IEEE Trans Ultrason Ferroelectr Freq Control

December 2003

Most recently, langasite and its isomorphs (LGX) have been advanced as potential substitutes for quartz, owing to their extremely high-quality (Q) factors. At least twice higher Q value of LGX than that of quartz has been reported. High Q translates into potentially greater stability.

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The surface characteristics of ethylene-vinyl acetate (EVA) were modified by argon, air, and oxygen plasma at atmospheric pressure. The surface energies of the EVA were evaluated by contact angles according to a sessile-drop method and adhesion energy (G(IC)) was estimated by a 180 degrees peel test with polyurethane (PU). After the plasma treatments, the surface free energies (or specific polar component) of the EVA increased about five times compared to that of virgin EVA.

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