Joon Ho Oh

Nano-patterned dual-layer ITO electrode of high brightness blue light emitting diodes using maskless wet etching

We propose a dual-layer transparent Indium Tin Oxide (ITO) top electrode scheme and demonstrate the enhancement of the optical output power of GaN-based light emitting diodes (LEDs). The proposed dual-layer structure is composed of a layer with randomly distributed sphere-like nano-patterns obtained solely by a maskless wet etching process and a pre-annealed bottom layer to maintain current spreading of the electrode. It was observed that the surface morphologies and optoelectronic properties are dependent on etching duration. This electrode significantly improves the optical output power of GaN-based LEDs with an enhancement factor of 2.18 at 100 mA without degradation in electrical property when compared to a reference LED.

Resistive switching properties of amorphous Pr0.7Ca0.3MnO3 films grown on indium tin oxide/glass substrate using pulsed laser deposition method

Amorphous Pr0.7Ca0.3MnO3 (APCMO) films, which were grown on indium tin oxide (ITO)/glass at room temperature (RT), were n-type materials. The APCMO/ITO/glass device exhibited an average transparency of 77% in the visible range with a maximum transparency of 84% at a wavelength of 530 nm. The Pt/APCMO/ITO device showed stable bipolar resistive switching behavior over 200 cycles that did not degrade after 105 s at RT. The resistance of the APCMO film decreased in both low- and high-resistance states with increasing device area. The resistive switching behavior of the Pt/APCMO/ITO device can be explained by the trap-charged space-charge-limited current mechanism.

Fabrication of monolithic polymer nanofluidic channels using nanowires as sacrificial templates.

We report a facile and reliable method to fabricate polymer-based monolithic nanofluidic channels. The nanochannels are obtained via three main steps: (1) fabrication of nanowire-transistor like structures, which are silver or zinc oxide nanowires horizontally bridging two electrodes made of zinc oxide on SiO(2)/Si substrates; (2) casting and curing polyimide solution on the nanowire structures; and (3) selective etching of the nanowire and electrode templates against the polyimide substrates. This process leads to the production of nanochannels with a diameter down to ∼ 50 nm. Our method is based on nanowires that are chemically synthesized whereas nanopattern fabrication conventionally relies on expensive equipment. Moreover, the polymer nanochannels are fabricated monolithically while a process of bonding two different materials is required in traditional methods where leakage problems are often identified at the interface. Construction of nanofluidic circuitry could be expected in the future based on the current work.