• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.387-387
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• 2010

최근 ZnO 박막은 투명 박막, 태양전지, LED 등으로의 응용을 위한 새로운 기능성 박막으로 활발히 연구되어 지고 있다. ZnO 기반의 투명 박막 트랜지스터는 상온에서 증착 가능하여 유리기판을 이용한 광학소자와 플라스틱 기판을 이용한 플럭서블 소자 같은 차세대 전자소자를 구현 할 수 있다. 본 연구에서는 RF Magnetron Sputtering System을 이용하여 coming 1737 유리기판 위에 ZnO 박막을 공정압력에 따라 증착하고, 투명 반도체에 적합한 활용을 위한 구조적, 광학적 분석을 실시하였다. 박막 증착 조건은 초기 압력 $1.0{\times}10^{-6}$Torr, RF 파워는 100W, Ar 유량은 100sccm, 그리고 증착온도는 상온이었다. 증착 압력은 $7.0{\times}10^{-3}$, $2.0{\times}10^{-2}$, $7.0{\times}10^{-2}$Torr로 변화시켰다. 표면 분석 (SEM, AFM) 결과 증착압력이 고진공으로 변화함에 따라 결정립들이 감소하였고 RMS roughness값이 낮아졌다. 그리고 XRD 분석을 통해 피크강도는 증가하고 FWHM은 감소함을 보이고 있는데 이는 결정성이 좋아짐을 나타낸다. 그리고 광학 투과도를 통해 가시광 영역에서의 높은 투과도(85% 이상)을 확인하였고, 고진공으로 변화함에 따라 밴드갭이 넓어지는 것을 확인하였다.

• Korean Journal of Optics and Photonics
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• v.15 no.3
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• pp.229-233
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• 2004

We propose a novel scheme to suppress the multiple-access interference(MAI) in coherent optical CDMA systems. This is based on a differential detection using the dual-control NOLM. For an experimental demonstration, two encoded channels we constructed and decoded. These decoded signals are sent to the dual-control NOLM and a high autocorrelation peak with suppressed MAI at the output of the NOLM is observed. Signal-to-interference ratio is improved by 7 ㏈.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.329-332
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• 2001

In this paper, it's shown that the saturable absorber Nd:LSB has a capability as a saturable absorber in Q-switching system. In the passively Q-switched 1.3${\mu}{\textrm}{m}$ Nd:YAG laser with saturable absorber, we theoretically investigated the optimized output mirror, peak power, output power, pulse width and output efficiency. The passively Q-switched Nd:YAG laser with saturable absorber Nd:LSB gives peak power of 30MW and pulse width of 6.23 ps at 30cm resonator length and output mirror reflectivity 98%. Consequently the output energies are 143, 200 and 209 $\mu$J at loss of 2.2%, 2.1% and 1.5%, respectively.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.184-184
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• 2016

대기압 플라즈마를 이용한 폴리머 합성은 기존의 합성방법에 비해 간단하고 쉽게 폴리머를 합성할 수 있다는 장점이 있다. 대부분의 폴리머는 합성온도가 $150^{\circ}C$ 이하이기 때문에 각 폴리머에 적합한 온도를 제어하는 것이 핵심이라 할 수 있다. 본 연구에서는 폴리머 합성온도를 제어하기 위하여 플라즈마 방전전극에 모노머를 직접 주입하지 않고 간접적인 방법을 선택했다. 그리고 모노머는 액체 공급 장치를 이용해 플라즈마의 가스량과 파워를 제어하면서 폴리머를 합성의 조건을 찾았다. AC 플라즈마를 이용해 methyl methacrylate($C_5H_8O_2$) 모노머를 폴리머로 합성했으며, 그 결과는 FTIR, XRD 등으로 분석하고 특성을 평가했다. FTIR의 결과, C-O, C-H, C=O 등의 전형적인 poly methyl methacrylate(PMMA)의 피크를 확인할 수 있었다. 그리고 XRD의 관찰결과 C1s 및 O1s의 각 binding energy가 각각 283, 285, 288 eV 및 533 eV 주변에서 확인되었다. 그리고 합성시간에 따라 폴리머의 두께가 비례해서 증가하는 것을 관찰할 수 있었다. 실험결과, AC 플라즈마를 이용한 폴리머합성은 가능한 것으로 확인되었으며 소형화 및 휴대가 가능하기 때문에 식품, 바이오, 의약품, 의료용품 등의 현장포장 등 여러 가지 용도로 활용이 가능할 것으로 판단된다.

• Journal of the Korean Vacuum Society
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• v.18 no.4
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• pp.288-295
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• 2009

We report the etch characteristics of GaAs and AlGaAs in the diffusion pump-based capacitively coupled $BCl_3$ plasma. Process variables were chamber pressure ($50{\sim}180$ mTorr), CCP power ($50{\sim}200\;W$) and $BCl_3$ gas flow rate ($2.5{\sim}10$ sccm). Surface profilometry was used for etch rate and surface roughness measurement after etching. Scanning electron microscopy was used to analyze the etched sidewall and surface morphology. Optical emission spectroscopy was used in order to characterize the emission peaks of the $BCl_3$ plasma during etching. We have achieved $0.25{\mu}m$/min of GaAs etch rate with only 5 sccm $BCl_3$ flow rate when the chamber pressure was in the range of 50{\sim}130 mTorr. The etch rates of AlGaAs were a little lower than those of GaAs at the conditions. However, the etch rates of GaAs and AlGaAs decreased significantly when the chamber pressure increased to 180 mTorr. GaAs and AlGaAs were not etched with 50 W CCP power. With $100{\sim}200\;W$ CCP power, etch rates of the materials increased over $0.3{\mu}m$/min. It was found that the etch rates of GaAs and AlGaAs were not always proportional to the increase of CCP power. We also found the interesting result that AlGaAs did not etched at 2.5 sccm $BCl_3$ flow rate at 75 mTorr and 100 W CCP power even though it was etched fast like GaAs with more $BCl_3$ gas flow rates. By contrast, GaAs was etched at ${{\sim}}0.3{\mu}m$/min at the 2.5 sccm $BCl_3$ flow rate condition. A broad molecular peak was noticed in the range of $500{\sim}700\;mm$ wavelength during the $BCl_3$ plasma etching. SEM photos showed that 10 sccm $BCl_3$ plama produced more undercutting on GaAs sidewall than 5 sccm $BCl_3$ plasma.

• Journal of the Korea Convergence Society
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• v.8 no.5
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• pp.161-167
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• 2017

We have fabricated and characterized $32{\times}32$ photonic quantum ring (PQR) laser arrays uniformly operable with $0.98{\mu}A$ per ring at room temperature. The typical threshold current, threshold current density, and threshold voltage are 20 mA, $0.068A/cm^2$, and 1.38 V. The top surface emitting PQR array contains GaAs multiquantum well active regions and exhibits uniform characteristics for a chip of $1.65{\times}1.65mm^2$. The peak power wavelength is $858.8{\pm}0.35nm$, the relative intensity is $0.3{\pm}0.2$, and the linewidth is $0.2{\pm}0.07nm$. We also report the wavelength division multiplexing system experiment using angle-dependent blue shift characteristics of this laser array. This photonic quantum ring laser has angle-dependent multiple-wavelength radial emission characteristics over about 10 nm tuning range generated from array devices. The array exhibits a free space detection as far as 6 m with a function of the distance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.21-26
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• 2016

This paper presents a step-down DC-DC buck converter with a CCM/DCM dual-mode function for the internal power stage of portable electronic device. The proposed converter that is operated with a high frequency of 1 MHz consists of a power stage and a control block. The power stage has a power MOS transistor, inductor, capacitor, and feedback resistors for the control loop. The control part has a pulse width modulation (PWM) block, error amplifier, ramp generator, and oscillator. In this paper, an external capacitor for compensation has been replaced with a multiplier equivalent CMOS circuit for area reduction of integrated circuits. In addition, the circuit includes protection block, such as over voltage protection (OVP), under voltage lock out (UVLO), and thermal shutdown (TSD) block. The proposed circuit was designed and verified using a $0.18{\mu}m$ CMOS process parameter by Cadence Spectra circuit design program. The SPICE simulation results showed a peak efficiency of 94.8 %, a ripple voltage of 3.29 mV ripple, and a 1.8 V output voltage with supply voltages ranging from 2.7 to 3.3 V.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.1
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• pp.466-474
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• 2014

This paper presents the line contention avoidance experiments with an optical switch, which was selected based on the comparison analysis and evaluation of the various characteristics. For example, the function, structure, strengths and weaknesses of the optical switches. After considering the nonblocking, modularity, upgrade ability and optical power loss of the several kind of the switch fabrics, a switch was selected. The selected switch fabric by using wavelength converters was controlled to avoid contention of the optical lines. In this experiment shows an example of three cases. As a result of this experiment, optical signal shows a changed peek of optical power in output. By showing a peak it confirms that the contention was avoided. By analyzing of changed optical power according to the channel setting time and release time to control of the switch could be determined. If this analysis applied to the network design, economical and efficient structures can be formed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.12
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• pp.2251-2257
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• 2006

We fabricated ZnO thin film successfully by using RF magnetron sputtering and investigated its potential for being utilized as the key material of piezoelectric device with the characterization of ZnO thin film such as such as crystallinity, surface morphology, c-axis orientation, film density. In thin study, $Ar/O_2$ gas ratio is fixed 70/30, RF power 125W, working pressure 8mTorr, distance between substrate and target 70mm, but the substrate temperature is varied from room temperature to $400^{\circ}C$. The relative intensity ($I_{(002)}/I_{(100)}$) or (002) peak in ZnO thin film deposited at $300^{\circ}$ was exhibited as 94%, then its FWHM was $0.571^{\circ}C$. Also, from the surface morphology evaluated by SEM and AFM, the film deposited at $300^{\circ}C$ showed uniform particle shape and excellent surface roughness of 4.08 m. The tendency of ZnO thin film density was exhibited to be denser with increasing substrate temperature but slightly decreased at near $400^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1023-1028
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• 2004

RF magnetron sputtering을 이용하여 증착한 투명전도성 ZnO 박막의 F 도핑량에 따른 전기, 구조, 광학적 특성에 대해 고찰하였다. 순수 ZnO와 ZnO : $ZnF_2$(1.3 wt%) 그리고 ZnO : $ZnF_2$(10 wt%) 3개의 타겟들을 2개씩 조합 각각의 rf 파워를 조절하여 co-sputtering 방법으로 $ZnF_2$ wt%를 변화시켜 박막내의 F 도핑량을 조절하였다. 증착된 박막들은 열처리에 따른 물성 변화를 분석하기 위해 $5{\times}10^{-7}$ torr 이하의 진공 분위기에서 $300^{\circ}C$에서 2 시간 동안 열처리하였다. XRD 분석 결과 제작된 모든 ZnO 박막은 (002) 우선 방위 특성을 보였고 F 도핑량 증가에 따라 (101), (110), (100) 방향의 약한 피크들이 나타났으며, 이러한 구조적 특성 변화는 이동도의 변화와 밀접한 관계가 있는 것으로 나타났다. Auger로 박막 내의 F 량을 분석한 결과 최대 5.9 at%의 F이 포함되어 있었으며, 열처리 후 캐리어 농도와 이동도는 증가하였고 최고 $37cm^2/Vs$의 이동도를 나타내었으며, 모든 박막들은 가시광 영역에서 81 % 이상의 투과도를 가졌다.