• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1295-1296
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• 2007

A lot of researches about dye-sensitized solar cell (DSC) are recently being conducted. Because DSC has several advantages to pass the limits of silicon solar cells such as a low manufacturing expense, a simple manufacturing process and its transparency. But most researches on DSC are still conducted about the unit cell and laboratory-centered. That is, present researches on DSC are not practical. Therefore, researches about large area cells and modules have to be prerequisites for DSC to have the practicality. Characteristics of large area DSC are so different from those of small area DSC in aspect of fill factor and efficiency. In this study, we made an experiment on finding suitable size of DSC that has the most effective power according to the variation of active area. In detail, the experiment was conducted about the optimum ratio of length to width and we introduced the ratio of active area to non-active area to find the active area which has the best output. Because small DSC doesn‘t have the best output in comparison with total area of cell although the smaller DSC has the better efficiency. As a result, we achieved the optimum ratio of length to width of 8:3 and active area of $8cm^2$ as the optimum size for upscaling DSC.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.80-80
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• 2000

Surface acoustic wave (SAW) devices have become more important as mobile telecommunication systems need h호-frrequency, low-loss, and down-sized components. Higher-frequency SAW divices can be more sasily realized by developing new h호-SAW-velocity materials. The ZnO/diamond/Si multilasyer structure is one of the most promising material components for GHz-band SAW filters because of its SAW velocity above 10,000 m/sec. Silicon carbide is also a potential candidate material for high frequency, high power and radiation resistive electronic devices due to its superior mechanical, thermal and electronic properties. However, high price of commercialized 6- or 4H-SiC single crystalline wafer is an obstacle to apply SiC to high frequency SAW devices. In this study, single crystalline 3C-SiC thin films were grown on Si (100) by MOCVD using bis-trimethylsilymethane (BTMSM, C7H20Si7) organosilicon precursor. The 3C-SiC film properties were investigated using SEM, TEM, and high resolution XRD. The FWHM of 3C-SiC (200) peak was obtained 0.37 degree. To investigate the SAW propagation characteristics of the 3C-SiC films, SAW filters were fabricated using interdigital transducer electrodes on the top of ZnO/3C-SiC/Si(100), which were used to excite surface acoustic waves. SAW velocities were calculated from the frequency-response measurements of SAW filters. A generalized SAW mode. The hard 3C-SiC thin films stiffened Si substrate so that the velocities of fundamental and the 1st mode increased up to 5,100 m/s and 9,140 m/s, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.451-451
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• 2010

최근들어 80인치 이상의 대경 고화질 display 및 휴대용 projection display 제작이 가능한 LCoS (Liquid Crystal on Silicon) display에 대한 관심이 높아지고 있다. LCoS projection display는 높은 개구율, 빠른 응답속도, 고화질, 대형 디스플레이 임에도 불구하고 낮은 제조단가 등의 여러 가지 장점을 가지고 있다. LCoS projection display의 핵심 기술로는 높은 투과도와 낮은 반사율을 갖는 유리기판, 무기 배향막 증착 기술, Si back plane과의 접합기술 등이 있다. 이 중 LCoS projection display 제작을 위한 첫 단계인 유리기판은 가시광선 영역에서 96% 이상의 높은 투과도와 3% 미만의 반사도를 요구하는 기술을 필요로 한다. 본 연구에서는 indium이 doping된 tin oxide (ITO)를 투명 전도성막으로 사용하고, $SiO_2/MgF_2$ 이중 박막을 반사방지막으로 채택하여 고투과도 및 저반사율을 갖는 유리기판 제조에 응용하였다. 먼저 15nm 두께의 ITO 박막을 DC sputtering을 이용하여 8-inch 크기의 corning1737 유리기판 상에 증착한 후, 그 반대편에 e-beam evaporation 장비를 사용하여 120nm 두께의 반사 방지막을 증착하였다. 또한 유리기판 상에 증착된 투명 전도성막의 표면개질을 위하여 Ar plasma를 이용하여 treatment를 수행하였다. 이 때 sputtering 조건은 DC power, Ar 유량 및 압력을 조절함으로서 높은 투과도를 갖는 최적의 조건을 구현하였고, e-beam evaporation을 이용한 반사방지막 증착 조건은 $SiO_2$와 $MgF_2$의 계면에서 빛의 반사를 최소화할 수 있는 최적의 조건을 구현하였다. 제작된 유리기판은 가시광선 영역에서 97% 이상의 투과도를 보였으며, 최대 2.8%의 반사율을 보여, LCoS display 제작에 적합함을 확인할 수 있었다. 또한 Ar plasma 처리 후 ITO 박막의 면저항 값은 $100\;{\omega}/{\Box}$, 표면 거칠기는 rms 값 기준 0.095nm, 접촉각 $20.8^{\circ}$의 특성을 보여, 타 index matched transparent conducting oxide가 coating된 유리기판에 비해 우수한 특성을 보였다.

• Journal of the Semiconductor & Display Technology
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• v.18 no.4
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• pp.30-34
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• 2019

We analyzed how the features in plasma information based virtual metrology (PI-VM) for SiO₂ etching depth with variation of 5% contribute to the prediction accuracy, which is previously developed by Jang. As a single feature, the explanatory power to the process results is in the order of plasma information about electron energy distribution function (PI_EEDF), equipment, and optical emission spectroscopy (OES) features. In the procedure of stepwise variable selection (SVS), OES features are selected after PI_EEDF. Informative vector for developed PI-VM also shows relatively high correlation between OES features and etching depth. This is because the reaction rate of each chemical species that governs the etching depth can be sensitively monitored when OES features are used with PI_EEDF. Securing PI_EEDF is important for the development of virtual metrology (VM) for prediction of process results. The role of PI_EEDF as an independent feature and the ability to monitor variation of plasma thermal state can make other features in the procedure of SVS more sensitive to the process results. It is expected that fault detection and classification (FDC) can be effectively developed by using the PI-VM.

• Journal of the Korea Organic Resources Recycling Association
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• v.19 no.4
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• pp.60-65
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• 2011

Siloxane is an organic silicon compound and is volatilized into the bio gas from anaerobic digestion. It causes failure of gas combustion engines using the bio gas. Siloxane emission characteristics should be identified to provide a proper siloxane control. This study focuses on characterizing siloxane emission in bio gas from an anaerobic digester of food wastewater operating from January to March. The concentrations of total average siloxane and cycle-siloxane D4 were detected to be 9.5 and $4.0mg\;siloxane/m^3$, respectively. The concentrations of cycle-siloxane and linear-siloxane were resulted in D4>D5>D6 and L4>L3>L5>L2, respectively. The total siloxane concentration was the lowest in January and the highest in March.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.6
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• pp.258-263
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• 2020

Silicon carbide (SiC) fibers mainly fabricated from polycarbosilane, a ceramic precursor, are applied as reinforcing materials for ceramic matrix composites (CMCs) because of their high temperature oxidation resistance, tensile strength, and light weight. In this study, continuous SiC fibers used to fabricate rope-type flexible heating elements capable of generating high-temperature heat (> 650℃). For high-efficiency heating elements, the resistance of SiC fiber rope was measured by 2-point probe method according to the cross-sectional area and length. In addition, the fabrication conditions of rope-type SiC fiber heating elements were optimized by controlling the oxygen impurities and the size of crystal grains present in the amorphous SiC fiber. As a result, the SiC fiber heating element having a resistance range of about 100~200 Ω exhibited an excellent power consumption efficiency of 1.5 times compared to that of the carbon fiber heating element.

• Applied Chemistry for Engineering
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• v.33 no.1
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• pp.78-82
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• 2022

Inorganic-organic hybrid perovskite solar cells have demonstrated considerable improvements, reaching 25.5% of certified power conversion efficiency (PCE) in 2020 from 3.8% in 2009 comparable to silicon photovoltacis. However, there remains important concern on the stability of perovskite solar cells under environmental conditions that should be solved prior to commercialization. In order to overcome the problem, we have introduced a small amount of octylammonium iodide with longer alkyl chain than volatile methylammonium iodide into MAPbI₃ perovskites. The presence of octylammonium into perovskites were confirmed using Fourier-transform infrared spectroscopy and UV-visible spectroscopy. Moreover, octylammonium-modified perovskite solar cells showed a PCE of 16.6% and enhanced moisture stability with an increased contact angle of 72.2° from 57.0°. This work demonstrated the importance of perovskite compositional engineering for improving efficiency and stability.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.3
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• pp.355-366
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• 2022

This paper proposes a microcode-based neural network accelerator controller for artificial intelligence accelerators that can be reconstructed using a programmable architecture and provide the advantages of low-power and ultra-small chip size. In order for the target accelerator to support various neural network models, the neural network model can be converted into microcode through microcode compiler and mounted on accelerator to control the operators of the accelerator such as datapath and memory access. While the proposed controller and accelerator can run various CNN models, in this paper, we tested them using the YOLOv2-Tiny CNN model. Using a system clock of 200 MHz, the Controller and accelerator achieved an inference time of 137.9 ms/image for VOC 2012 dataset to detect object, 99.5ms/image for mask detection dataset to detect wearing mask. When implementing an accelerator equipped with the proposed controller as a silicon chip, the gate count is 618,388, which corresponds to 65.5% reduction in chip area compared with an accelerator employing a CPU-based controller (RISC-V).

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.3080-3087
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• 2023

Thermoelectric (TE) materials working in radioisotope thermoelectric generators are irradiated by neutrons throughout its service; thus, investigating the neutron irradiation stability of TE devices is necessary. Herein, the influence of neutron irradiation with fluences of 4.56 × 10¹⁰ and 1 × 10¹³ n/cm² by pulsed neutron reactor on the electrical and thermal transport properties of n-type Bi₂Te_2.7Se_0.3 and p-type Bi_0.5Sb_1.5Te₃ thermoelectric alloys prepared by cold-pressing and molding is investigated. After neutron irradiation, the properties of thermoelectric materials fluctuate, which is related to the material type and irradiation fluence. Different from p-type thermoelectric materials, neutron irradiation has a positive effect on n-type Bi₂Te_2.7Se_0.3 materials. This result might be due to the increase of carrier mobility and the optimization of electrical conductivity. Afterward, the effects of p-type and n-type TE devices with different treatments on the output performance of TE devices are further discussed. The positive and negative effects caused by irradiation can cancel each other to a certain extent. For TE devices paired with p-type Bi_0.5Sb_1.5Te₃ and n-type Bi₂Te_2.7Se_0.3 thermoelectric legs, the generated power and conversion efficiency are stable after neutron irradiation.

• Journal of Adhesion and Interface
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• v.24 no.2
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• pp.60-63
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• 2023

The AlGaN/GaN heterostructure has high electron mobility due to the two-dimensional electron gas (2-DEG) layer, and has the characteristic of high breakdown voltage at high temperature due to its wide bandgap, making it a promising candidate for high-power and high-frequency electronic devices. Despite these advantages, there are factors that affect the reliability of various device properties such as current collapse. To address this issue, this paper used metal-organic chemical vapor deposition to continuously deposit AlGaN/GaN heterostructure and SiN passivation layer. Material and electrical properties of GaN HEMTs with/without SiN cap layer were analyzed, and based on the results, low-frequency noise characteristics of GaN HEMTs were measured to analyze the conduction mechanism model and the cause of defects within the channel.