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Chanwoo Kim,Geunyoung Yeom,Sejin Kyung,Yonghyuk Lee 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.4
(DBD)-type atmospheric-pressure plasma-enhanced chemical vapor deposition (AP-PECVD) system at a low temperature of 400 C, and their growth characteristics were investigated. The CNTs grown using He (6 slm)/C2H2 (90 sccm) AP-PECVD with additive gases (NH3, N2) for 5 minutes at 400C after a pretreatment were multi-layer CNTs with diameter of 20 – 50 nm and uniform lengths of 1.5 – 2 μm. FT-Raman spectroscopy showed that the grown CNTs were multi-wall CNTs with a D-band/G-band intensity ratio of 0.9. Transmission electron microscopy of the AP-PECVDgrown CNTs showed that the CNT had a 30-nm outer diameter and a 7-nm hollow inner diameter with a Ni particle on the top of the tube.
Jungkyun Park,Geunyoung Yeom,JongHyeuk Lim,Kyongnam Kim 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.2
The characteristics of a large-size internal-type inductively coupled plasma (ICP) source having a ``double-comb-type" antenna have been investigated for the processing of a large-area flat-panel display substrate having a size of 2,300 mm × 2,000 mm, and its characteristics were compared with those for an ICP source having a ``serpentine-type" antenna. The ICP source with the ``double-comb-type" antenna showed a lower impedance, a higher plasma uniformity, and a higher plasma density compared to the ICP source with the ``serpentine-type" antenna. The measured plasma density and uniformity of the ICP source with the ``double-comb-type" antenna were higher than 8.5 × 10 10/㎤ and lower than 14%, respectively, at a 10 kW rf power and 15 mTorr of Ar. The etch uniformity of the photoresist within the substrate was about 12.5% at a 8 kW rf power and 15 mTorr Ar/O₂ (7 : 3). The characteristics of a large-size internal-type inductively coupled plasma (ICP) source having a ``double-comb-type" antenna have been investigated for the processing of a large-area flat-panel display substrate having a size of 2,300 mm × 2,000 mm, and its characteristics were compared with those for an ICP source having a ``serpentine-type" antenna. The ICP source with the ``double-comb-type" antenna showed a lower impedance, a higher plasma uniformity, and a higher plasma density compared to the ICP source with the ``serpentine-type" antenna. The measured plasma density and uniformity of the ICP source with the ``double-comb-type" antenna were higher than 8.5 × 10 10/㎤ and lower than 14%, respectively, at a 10 kW rf power and 15 mTorr of Ar. The etch uniformity of the photoresist within the substrate was about 12.5% at a 8 kW rf power and 15 mTorr Ar/O₂ (7 : 3).
HyoungCheol Lee,GeunYoung Yeom,Jin Koog Shin,Sung Il Baik,Yoo Jin Lee,Young Woon Kim 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.1
In this study, silicon thin films were deposited by using a transformer-coupled-plasma chemicalvapor deposition (TCPCVD) technique using SiH4/H2/PH3, and the effects of rf power on the structural and the electrical properties of the deposited thin films were investigated for applications to silicon solar cells. Increasing the rf power from 50 to 500 W increased the percent of crystalline silicon in the film from 42 to about 79 %. The increase in crystalline silicon was mostly attributed to an increase in the number of nanosized crystalline silicon grains having grain sizes from 3 to 15 nm. The increase in crystalline percent was also accompanied by an increase in the stress in the film. The increased crystalline silicon percent in the films increased the dark conductivity and, at 500 W of rf power, a dark conductivity of 10 −1cm−1 could be obtained for a 40-nm-thick film, which is applicable to silicon-based solar cells.
Characteristics of a Pin-to-Plate Dielectric Barrier Discharge in Helium
Yong-Hyuk Lee,GeunYoung Yeom 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.1
In this study, the characteristics of a modified dielectric barrier discharge (DBD) (that is, a pin-to-plate DBD) in He have been studied as a function of the applied AC voltage, the air gap between the electrodes, and the pin density of the powered electrode. The pin-to-plate DBD showed typical current-voltage characteristics similar to those of a corona discharge. The optimum air gap between the electrodes at a given applied voltage was 4 mm, for which the consumed power was a maximum. When the air gap was larger than 4 mm, the discharge changed from a glow discharge to a filamentary discharge. An increase in the pin density from 4 to 16 pins/cm2 also increased the consumed power at a given voltage and at a fixed air gap. When the optical emission intensities from He metastable and oxygen atoms from the feed He gas and from the residual air, respectively were investigated by using an optical emission spectrometer, the highest optical emission intensities from He metastable and oxygen atoms was obtained for a pin density of 16 pins/cm2 at a given voltage and a fixed air gap. The photoresist ashing rate using the residual oxygen in He was also the highest when the pin density was 16 pins/cm2 and when the air gap was 4 mm, possibly because the dissociated oxygen atomic density in the plasma and the power consumption were highest.
Effect of GaN Microlens Array on Efficiency of GaN-Based Blue-Light-Emitting Diodes
Kim, Dongwoo,Lee, Hyoyoung,Cho, Namgil,Sung, Younjoon,Yeom, Geunyoung The Japan Society of Applied Physics 2005 Japanese journal of applied physics Vol.44 No.1
<P>In this study, GaN-based vertical light-emitting diodes (VLEDs) were fabricated by a laser lift-off (LLO) process and the effects of microlens formation by plasma etching on the optical properties of the LLO GaN-based VLED devices were investigated. By forming a 5–10 μm microlens array on the LLO GaN-based VLEDs, the measured light emission intensities at 460 nm and in the direction normal to the surface of the device increased by approximately 40% and 100% compared with those of the LLO GaN-based VLED without the microlens array for 10 μm and 5 μm microlens arrays, respectively.</P>
Neutralized fluorine radical detection using single-walled carbon nanotube network
Jung, Sehun,Hong, Seunghyun,Park, Byoungjae,Choi, Jaeboong,Kim, Youngjin,Yeom, Geunyoung,Baik, Seunghyun Elsevier 2008 Carbon Vol.46 No.1
<P><B>Abstract</B></P><P>It is known that single-walled carbon nanotubes (SWCNTs) can be functionalized by fluorine gas. Here, we report neutralized fluorine radical detection using a matted sheet of SWCNTs, prepared by alternating current dielectrophoresis. Upon exposure to neutralized radicals containing fluorine atoms in a plasma, as model analytes, the conductance of the SWCNT matt showed fast modulation. The transduction mechanism was investigated by electrical transport measurements, X-ray photoelectron spectroscopy and Raman spectroscopy. Metallic nanotubes were shown to react covalently to the near exclusion of semiconducting species. The selectivity was promoted by the curvature-induced strain of the nanotubes. The results open new opportunities for the detection of fluorine radicals at specific locations inside the reaction zone using a simple, miniaturized carbon nanotube network.</P>