Moon-Youn Jung

Photolithography-based carbon nanotubes patterning for field emission displays

Carbon nanotubes (CNTs) emitters were successfully patterned in small pixels (50×50 μm2) by using photolithography process on a hard metal electrode for field emission displays (FEDs) application. The CNTs particles in the patterned pixels were uniformly distributed on 2-inch diagonal substrates. The maximum diameter of CNTs particles could be controlled less than 20 μm. After patterning and heat treatment process below 300°C, most of CNTs bundles on the cathode electrode were aligned perpendicular to the substrates. The threshold electric field of emission for patterned CNTs was about 4.2 V μm−1 and the field enhancement factor derived from the Fowler–Nordheim plots of the electron emissions was about 100 000 in the high voltage region. This newly developed process can be applicable to field emitter arrays for high resolution FEDs.

Wide tuning range wavelength-swept laser with a single SOA at 1020 nm for ultrahigh resolution Fourier-domain optical coherence tomography

In this study, we demonstrated a wide tuning range wavelength-swept laser with a single semiconductor optical amplifier (SOA) at 1020 nm for ultrahigh resolution, Fourier-domain optical coherence tomography (UHR, FD-OCT). The wavelength-swept laser was constructed with an external line-cavity based on a Littman configuration. An optical wavelength selection filter consisted of a grating, a telescope, and a polygon scanner. Before constructing the optical wavelength selection filter, we observed that the optical power, the spectrum bandwidth, and the center wavelength of the SOA were affected by the temperature of the thermoelectric (TE) cooler in the SOA mount as well as the applied current. Therefore, to obtain a wide wavelength tuning range, we adjusted the temperature of the TE cooler in the SOA mount. When the temperature in the TE cooler was 9 °C, our swept source had a tuning range of 142 nm and a full-width at half-maximum (FWHM) of 121.5 nm at 18 kHz. The measured instantaneous spectral bandwidth (δλ) is 0.085 nm, which was measured by an optical spectrum analyzer with a resolution bandwidth of 0.06 nm. This value corresponds to an imaging depth of 3.1 mm in air. Additionally, the averaged optical power of our swept source was 8.2 mW. In UHR, FD/SS-OCT using our swept laser, the measured axial resolution was 4.0 μm in air corresponding to 2.9 μm in tissue (n = 1.35). The sensitivity was measured to be 93.1 dB at a depth of 100 μm. Finally, we obtained retinal images (macular and optic disk) and a corneal image.

Patterning technology of carbon nanotubes for field emission displays

Patterning technology of fine carbon nanotube (CNT) pixels on a hard metal has been developed by using photolithography process for field emission displays (FEDs). The photolithography method produced much sharper and smaller CNT pixels compared with those made by the conventional screen-printing process. The CNTs in the patterned pixels by photolithography were uniformly distributed in a 2 in. diagonal area. The density of CNT bundles in the patterned pixels was about 10/μm2. After patterning and heat treatment process below 300 °C, most of CNT bundles on the cathode were aligned perpendicular to the substrate. The turn-on field of patterned CNTs was less than 4.2 V/μm and the current density was about 2.1 mA/cm2 at 6 V/μm. This process might be applicable to field emitter arrays for high resolution FEDs.

Fourier Domain Optical Coherence Tomography for Retinal Imaging with 800-nm Swept Source: Real-time Resampling in k-domain

In this study, we demonstrated Fourier-domain/swept-source optical coherence tomography (FD/SS-OCT) at a center wavelength of 800 nm for in vivo human retinal imaging. A wavelength-swept source was constructed with a semiconductor optical amplifier, a fiber Fabry-Perot tunable filter, isolators, and a fiber coupler in a ring cavity. Our swept source produced a laser output with a tuning range of 42 nm (779 to 821 nm) and an average power of 3.9 mW. The wavelength-swept speed in this configuration with bidirectionality is 2,000 axial scans per second. In addition, we suggested a modified zero-crossing method to achieve equal sample spacing in the wavenumber (k) domain and to increase the image depth range. FD/SS-OCT has a sensitivity of ~89.7 dB and an axial resolution of 10.4 μm in air. When a retinal image with 2,000 A-lines/frame is obtained, an acquisition speed of 2.0 fps is achieved.

Etch Characteristics of Cr by Using Cl2 / O 2 Gas Mixtures with Electron Cyclotron Resonance Plasma

We investigated the etch characteristics of chromium films by using Cl 2 /O 2 gas mixtures with electron cyclotron resonance plasma. In order to examine the chemical etch characteristics of Cl 2 /O 2 gas plasma, we examined the etch rate with various gas mixing ratios. By X-ray photoelectron spectroscopy (XPS), the surface reaction on the chromium films during the etch was examined. At the same time, the plasma characteristics were examined by optical emission spectroscopy, From XPS analyses, it was confirmed that a chromium oxychloride (CrCl 2 O x ) layer was formed on the surface by the etch using Cl 2 /O 2 gas mixtures. We observed a new characteristic emission line at 517 nm during the etch of chromium films with Cl 2 /O 2 gas mixtures, using optical emission spectroscopy, It was found that the peak intensity of this emission line had a similar behavior to the etch rate. It was proposed that the emission line of 517 nm should result from chromium compounds with the oxidation state of Cr 3+ .

Novel lithography process for extreme deep trench by using laminated negative dry film resist

For the fabrication of MEMS(micro electro mechanical system) devices such as HAR(high-aspect-ratio) microstructures with an extreme deep trench, a novel lithography method was newly developed in this study. In the case of the deep trench, the liquid photoresist is not or very thinly coated at edge parts of the trench boundary. And, if a very thick resist coated, it is nearly impossible to develop the photoresist in the deep trench. To solve these problems, it is capped by laminating negative DFR(dry film resist) film on the cavity opening of the deep trench. Then positive photoresist is conventionally coated and patterned by the same photomask for the deep trench. To apply electric signals from outside to inside of the trench, aluminum on sidewall and bottom of the deep trench was successfully patterned by newly developed lithography method.

L‐3: Late‐News Paper: Active‐Controlled Diode Emitters with Thin‐Film Transistor and Carbon Nanotubes for FED Applications

A new cathode technology of active-controlled diode emitters with a-Si high-voltage TFTs and carbon nanotubes (CNTs) is suggested for field emission displays (FEDs). The a-Si TFT controlled electron emissions from the multiwall CNTs actively, resulting in great improvement in emission stability and the possibility of low voltage matrix-addressable operations of diode type cathodes. This technology can provide a new breakthrough in FEDs.

P- 41: A Novel Patterning Technology of Fine-pitched CNT Pixels for Field Emitter Arrays

A novel patterning technology of fine-pitched carbon nanotube (CNT) pixels on a thin metal has been developed by lift-off process for field emitter arrays (FEAs). The lift-off method provides even smaller CNT pixels compared with those made by conventional screen-printing and photolithography processes. SEM images demonstrated that the smallest pitch and the size of patterned pixels were 15 μm × 15 μm and 7 μm × 7 μm, respectively. After patterning and heat treatment process at 300°C, most of CNT bundles on the cathodes were aligned perpendicular to the substrate. The density of CNT bundles in the patterned pixels was 10–20/μm2. The turn-on field of patterned CNTs was less than 2.5 V/μm and the current density was 3.2 mA/cm2 at 3.5 V/μm.

Characteristics of LIGA PMMA micromirror for MOEM optical switch application

We investigated characteristic of LIGA PMMA (polymethylmethacrylate) micromirror for MOEM optical switch application. The optical switching device was designed and fabricated in multi-layered polysilicon using the LPCVD process. We performed adhesion test on silicon and silicon oxide and acid test by anhydrous HF GPE (gas-phase etching) and 6:1 BHF wet etch processes for thin and thick gold-coated PMMA micromirrors. Normalized reflectance and surface roughness are measured by UV Spectrometer and WYKO interferometer, respectively. We found that the reflectance of gold-coated PMMA micromirror on the silicon surface was above 90%.

Novel process for high reflectivity of Al sidewalls of optical mirrors using KrF excimer laser annealing

A study of the laser annealing effect for the thermal evaporated Al thin film onto micromirrors of optical switch and (100) Si subtrates is reported. The 2 X 2 optical switches has been fabricated through DRIE process. The input laser energy has been changed from 150 mJ/pulse to 350 mJ/pulse and the number of pulse also changed. The surface morphology is investigated by SEM micrograph and the roughness is examined by AFM. The reflectivities of the samples are measured by IR reflectometer and the results are normalized with gold. In case of the energy above 200 mJ/pulse, the reflectivities are improved up to above 0.98 from the incident beam region of 1300 nm to 1550 nm. The improvement of reflectivity is caused by the reflow process induced laser annealing. By the reflow process the grain have been growth and agglomerated for the surface planarization. The energy for planarization is sufficient as 1 pulse incident laser beam. According to the number of pulses, reflectivity is somewhat degraded by excess heat of reflow in case of above 5 pulses. There is minor morphology change with input laser energy.