• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.478.1-478.1
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• 2014

We investigated $MoO_3$ graded ITO electrodes for organic solar cells (OSCs) without PEDOT:PSS buffer layer. The effect of $MoO_3$ thickness on the electrical, optical, and structural properties of $MoO_3$ graded ITO anodes prepared by RF/DC magnetron co-sputtering system using $MoO_3$ and ITO targets was investigated. At optimized conditions, we obtained $MoO_3$ graded ITO electrodes with a low sheet resistance of 13 Ohm/square, a high optical transmittance of 83% and a work function of 4.92 eV, comparable to conventional ITO films. Due to the existence of $MoO_3$ on the ITO electrodes, OSCs fabricated on $MoO_3$ graded ITO electrode without buffer layer successfully operated. Although OSCs fabricated on ITO anode without buffer layer showed a low power conversion efficiency of 1.249%, OSCs fabricated on $MoO_3$ graded ITO electrode without buffer layer showed a outstanding cell performance of 2.545%. OSCs fabricated on the $MoO_3$ graded ITO electrodes exhibited a fill factor of 61.275%, a short circuit current of 7.439 mA/cm2, an open circuit voltage of 0.554 V, and a power conversion efficiency of 2.545%. Therefore, $MoO_3$ graded ITO electrodes can be considered a promising transparent electrode for cost efficient and reliable OSCs because it could eliminate the use of acidic PEDOT:PSS buffer layer.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.473.1-473.1
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• 2014

We report on the characteristics of Zr-doped $In_2O_3$ (IZrO) films prepared by DC-RF magnetron cosputtering of $In_2O_3$ and $ZrO_2$ targets for use as a transparent electrode for high efficient organic solar cells (OSCs). The effect of $ZrO_2$ doping power on electrical, optical, structural, and surface morphology of the IZrO film was investigated in detail. At optimized $ZrO_2$ RF power of 50 W, the IZrO film exhibited a low sheet resistance of 20.71 Ohm/square, and a high optical transmittance of 83.9 %. Furthermore, the OSC with the IZrO anode showed a good cell-performance: fill factor of 61.71 %, short circuit current (Jsc) of $8.484mA/cm^2$, open circuit voltage (Voc) of 0.593 V, and power conversion efficiency (PCE) of 3.106 %. In particular, the overall OSC characteristics of the cell with the IZrO anode were comparable to those of the OSC with the conventional Sn-doped $In_2O_3$ (FF of 65.03 %, Jsc of $8.833mA/cm^2$, Voc of 0.608 V, PCE of 3.495 %), demonstrating that the IZrO anode is a promising alternative to ITO anode in OSCs.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.54.2-54.2
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• 2010

최근까지는 주로 비정질 실리콘이 디스플레이의 채널층으로 상용화 되어왔다. 비정질 실리콘 기반의 박막 트랜지스터는 제작의 경제성 및 균일성을 가지고 있어서 널리 상용화되고 있다. 하지만 비정질 실리콘의 구조적인 문제인 낮은 전자 이동도(< $1\;cm^2/Vs$)로 인하여 디스플레이의 대면적화에 부적합하며, 광학적으로 불투명한 특성을 갖기 때문에 차세대 디스플레이의 응용에 불리한 점이 있다. 이런 문제점의 대안으로 현재 국내외 여러 연구 그룹에서 산화물 기반의 반도체를 박막 트랜지스터의 채널층으로 사용하려는 연구가 진행중이다. 산화물 기반의 반도체는 밴드갭이 넓어서 광학적으로 투명하고, 상온에서 증착이 가능하며, 비정질 실리콘에 비해 월등히 우수한 이동도를 가짐으로 디스플레이의 대면적화에 유리하다. 특히 Zinc Oxide의 경우, band gap이 3.4eV로써, transparent conductors, varistors, surface acoustic waves, gas sensors, piezoelectric transducers 그리고 UV detectors 등의 많은 응용에 쓰이고 있다. 또한, a-Si TFTs에 비해 ZnO-based TFTs의 경우 우수한 소자 성능과 신뢰성을 나타내며, 대면적 제조시 우수한 균일성 및 낮은 생산비용이 장점이다. 그러나 ZnO-baesd TFTs의 경우 일정한 bias 아래에서 threshold voltage가 이동하는 문제점이 displays의 소자로 적용하는데 매우 중요하고 문제점으로 여겨진다. 특히 gate insulator와 channel layer사이의 interface에서의 defect에 의한 charge trapping이 이러한 문제점들을 야기한다고 보고되어진다. 본 연구에서는 Zinc Oxide 기반의 박막 트랜지스터를 DC magnetron sputtering을 이용하여 상온에서 제작을 하였다. 또한, $Si_3N_4$ 기판 위에 electron cyclotron resonance (ECR) $O_2$ plasma 처리와 plasma-enhanced chemical vapor deposition (PECVD)를 통하여 $SiO_2$ 를 10nm 증착을 하여 interface의 개선을 시도하였다. 그리고 TFTs 소자의 출력 특성 및 전이 특성을 평가를 하였고, 소자의 field effect mobility의 값이 향상을 하였다. 또한 Temperature, Bias Temperature stability의 조건에서 안정성을 평가를 하였다. 이러한 interface treatment는 안정성의 향상을 시킴으로써 대면적 디스플레의 적용에 비정질 실리콘을 대체할 유력한 물질이라고 생각된다.

• Advances in Traditional Medicine
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• v.7 no.5
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• pp.549-555
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• 2008

Bupleuri radix (Umbelliferae), the dried root of Bupleurum Chinense DC, has been clinically used to mitigate pain sensation. The descending pain control system consists of three major components, and modulation of pain in the periaqueductal gray is the most extensively studied descending pain control system. However, the relation of Bupleuri radix on the descending pain control system has not been clarified. In the present study, modulation of the aqueous extract of Bupleuri radix on glycine-induced ion current in the acutely dissociated periaqueductal gray neurons was investigated by using nystatin-perforated patch-clamp technique under voltage-clamp condition. In the present results, the glycine-induced ion current was significantly suppressed by 0.1 mg/ml Bupleuri radix, while treatment with $10^{-5}\;M$ naltrexone, opioid receptor antagonist, alleviated Bupleuri radix-induced inhibition on glycine-induced ion current. The present study showed that the aqueous extract of Bupleuri radix may activate descending pain control system through inhibition on glycine-induced ion current in the periaqueductal gray neurons and this effect is mediated by opioid receptors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.213-216
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• 2001

Etching behaviors of ferroelectric $YMnO_3$ thin films were studied by an inductively coupled plasma (ICP). Etch characteristic on ferroelectric $YMnO_3$ thin film have been investigated in terms of etch rate, selectivity and etch profile. The maximum etch rate of $YMnO_3$ thin film is $300{\AA}/min$ at $Ar/Cl_2$ of 2/8, RF power of 800W, dc bias voltage of 200V, chamber pressure of 15mTorr and substrate temperature of $30^{\circ}C$. Addition of $CF_4$ gas decrease the etch rate of $YMnO_3$ thin film. From the results of XPS analysis, YFx compounds were found on the surface of $YMnO_3$ thin film which is etched in $Ar/Cl/CF_{4}$ plasma. The etch profile of $YMnO_3$ film is improved by addition of $CF_4$ gas into the $Ar/Cl_2$ plasma. These results suggest that fluoride yttrium acts as a sidewall passivants which reduce the sticking coefficient of chlorine on $YMnO_3$.

• Journal of Power Electronics
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• v.18 no.3
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• pp.931-943
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• 2018

Wireless power transfer (WPT) technology has been the focus of a lot of research due to its safety and convenience. The Z-source inverter (ZSI) was introduced into WPT systems to realize improved system performance. The ZSI regulates the dc-rail voltage in WPT systems without front-end converters and makes the inverter bridge immune to shoot-through states. However, when the WPT system is combined with a ZSI, the system parameters must be configured to prevent the ZSI from entering an "accidental shoot-through" (AST) state. This state can increase the THD and decrease system power and efficiency. This paper presents a mathematical analysis for the characteristics of a WPT system and a ZSI while addressing the causes of the AST state. To deal with this issue, the impact of the system parameters on the output are analyzed under two control algorithms and the primary compensation capacitance range is derived in detail. To validate the analysis, both simulations and experiments are carried out and the obtained results are presented.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.863-866
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• 1999

(Ba,Sr)$TiO_3$ thin films have attracted groat interest as new dielectric materials of capacitors for ultra-large-scale integrated dynamic random access memories (ULSI-DRAMs) such as 1 Gbit or 4 Gbit. In this study, inductively coupled $BCl_3/Cl_2$/Ar plasmas was used to etch (Ba,Sr)$TiO_3$ thin films. RF power/dc bias voltage = 600 W/-250 V and chamber pressure was 10 mTorr. The $Cl_2/(Cl_2+Ar)$ was fixed at 0.2, the (Ba,Sr)$TiO_3$ thin films were etched adding $BCl_3$. The highest (Ba,Sr)$TiO_3$ etch rate is 480$\AA/min$ at 10 % $BCl_3$ adding to $Cl_2$/Ar. The characteristics of the plasmas were estimated using optical emission spectroscopy (OES). The change of Cl, B radical density measured by OES as a function of $BCl_3$ percentage in $Cl_2$/Ar. The highest Cl radical density was shown at the addition of 10% $BCl_3$ to $Cl_2$/Ar. To study on the surface reaction of (Ba,Sr)$TiO_3$ thin films was investigated by XPS analysis. Ion enhancement etching is necessary to break Ba-O bond and to remove $BaCl_2$. There is a little chemical reaction between Sr and Cl, but Sr is removed by physical sputtering. There is a chemical reaction between Ti and Cl, and Tic14 is removed with ease. The cross-sectional of (Ba,Sr)$TiO_3$ thin film was investigated by scanning electron microscopy (SEM), the etch slope is about $65\;{\sim}\;70$.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.154-154
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• 2017

Ti-6Al-4V alloys are widely used as metal-lic biomaterials in dentistry and orthopedics due to its excellent biocompatibility and me-chanical properties. However, because of low biological activity, it is difficult to form bone growth directly on the surface of titanium implants. For this reason, surface treatment of plasma electrolytic oxidation(PEO) was used for dental implants. To enhance bioac-tivity on the surface, strontium(Sr) and sili-con(Si) ions can be added to PEO treated sur-face in the electrolyte containing these ions. The presence of Sr in the coating enhances osteoblast activity and differentiation, where-as it inhibits osteoclast production and prolif-eration. And Si has been found to be essen-tial for normal bone, cartilage growth, and development. In this study, electrochemical characteristics of Ca, P, Sr, and Si ions from PEO-treated Ti-6Al-4V alloy surface was re-searched using various experimental instruments. DC power is used and Ti-6Al-4V al-loy was subjected to a voltage of 280 V for 3 minutes in the electrolyte containing 5, 10, 20M% Sr ion and 5M% Si ion. The morphol-ogies of PEO-treated Ti-6Al-4V alloy by electrochemical anodization were examined by field-emission scanning electron micro-scopes (FE-SEM), energy dispersive x-ray spectroscopy (EDS), x-ray diffraction (XRD) and corrosion analysis using AC impedance and potentiodynamic polarization test in 0.9% NaCl solution at similar body tempera-ture using a potentiostat with a scan rate of 1.67mV/s and potential range from -1500mV to + 2000mV.

• Progress in Superconductivity
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• v.8 no.2
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• pp.164-168
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• 2007

We developed a SQUID magnetometer based on Double Relaxation Oscillation SQUID(DROS) for measuring magnetocardiography(MCG). Since DROS provides a 10 times larger flux-to-voltage transfer coefficient than the conventional DC-SQUID, simple flux-locked loop electronics could be used for SQUID operation. Especially, we adopted an external feedback to eliminate the magnetic coupling with adjacent channels. When the DROS magnetometer was operated inside a magnetically shielded room, average magnetic field noise was about 5 $fT/^{\surd}Hz$ at 100 Hz. Using the DROS magnetometer, we constructed a multichannel MCG system. The system consisted of 61 magnetometers are arranged in a hexagonal structure and measures a vertical magnetic-field component to the chest surface. The distance between adjacent channels is 26 mm and the magnetometers cover a circular area with a diameter of 208 mm. We recorded the MCG signals with this system and confirmed the magnetic field distribution and the myocardinal current distribution.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.6
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• pp.545-550
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• 2013

We present a tactile information transceiver using a friction-tunable slider-pad. While previous tactile information devices were focused on either input or output functions, the present device offers lateral position/vertical direction detection and texture expression. In characterizing the tactile input performance, we measured the capacitance change due to the displacement of the slider-pad. The measured difference for a z-axis click was 0.146 nF/$40{\mu}m$ when the x-y axis navigation showed 0.09 nF/$750{\mu}m$ difference. In characterizing the texture expression, we measured the lateral force due to a normal load. We applied a voltage between parallel electrodes to induce electrostatic attraction in DC and AC voltages. We measured the friction under identical fingertip action conditions, and obtained friction in the range of 32-152 mN and lateral vibration in the force range of 128.1 mN at 60 V, 2 Hz. The proposed device can be applied to integrated tactile interface devices for mobile appliances.