• Korean Journal of Crystallography
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• v.6 no.2
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• pp.111-117
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• 1995

TiO2 thin films were prepared on a (100)silicon wafer using a chemical vapor deposition(CVD) method. The deposition experiments were performed using the TTIP in the deposition temperature ransing from 200 content. The deposition rate of TiO2 was increased with the substrate temperature and the oxygen content. The thickness of the deposited thin film and the compositional analysis of this thin films with theoxygen content were measured using Ellipsometry, SEM and ESCA, respectively. The deposited thin film was composed of a bilayer, external TiO2 and internal Ti. Carbon as a residual impurity was found to remain when zero sccm O2 was purged into a reaction chamber and the composition of the deposited thin film was found to change Ti into TiO in a deeper layer. However, when 600sccm O2 was supplied to a reaction chamber, it has been found to reside less carbon content than without O2. Finally, in the condition of 1200sccm O2, no impurity level of carbon was observed and a deeper layer consisted of the Ti composite, even though the deposited surface was composed of TiO2.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1574-1576
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• 2003

Carbon nanotubes (CNTs) were grown on the TiN-coated silicon substrate with different thickness of Ni and Co catalysts layer at $600^{\circ}C$ using inductively coupled plasma-chemical vapor deposition (ICP-CVD). The Ni and Co catalysts were formed using the RF magnetron sputtering system with various deposition times. It was found that the growth of CNTs was strongly influenced by the surface morphology of Ni and Co catalysts. With increasing deposition time, the thickness of catalysts increased and the grain boundary size of catalysts increased. The surface morphology of catalysts and CNTs were elucidated by SEM. The Raman spectrum further confirmed the graphitic structure of the CNTs. The turn-on field of CNTs grown on Ni and Co catalysts was about 2.7V/pm and 1.9V/pm respectively. Field emission current density of CNTs grown on Ni and Co catalysts was measured as $11.67mA/cm^2$ at $5.5V/{\mu}m$ and $1.5mA/cm^2$ at $5.5V/{\mu}m$ respectively.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1938-1940
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• 2003

본 연구는 요소 센서 제작을 위한 과정으로서, 전기화학적 방법을 이용한 다공질 실리콘 구조 형성과, PDV(Physical Vapor Deposition) 법에 의한 백금 박막 코팅 및 전기화학적 전도성 고분자 코팅과 urease 고정화 단계를 고찰하고 감도 특성을 제시 하였다. 전극 기질로서 B을 도우핑한 p-type 실리콘웨이퍼를 사용하였고, HF:$C_2H_5OH:H_2O$=1:2:1의 부피비를 갖는 에칭 용액에서 5분간 -7 $mA/cm^2$의 일정 전류를 가하여 폭 2 ${\mu}m$, 깊이 10 ${\mu}m$의 다공질 실리콘(PS) 충을 형성하였다. 그 위에 200 ${\AA}$의 Ti 층을 underlayer로서 증착하고, 2000 ${\AA}$의 Pt를 중착하여 PS/Pt 박막 전극을 제작하고, 전도성 고분자로서 polypyrrole (PPy), 또는 poly(3-mehylthiophene) (P3MT)을 전기화학적으로 코팅한 후, urease(EC 3.5.1.5, type III, Jack Bean, Sigma)를 고정화 하였다. 고정화 시 전해질 수용액의 pH는 7.4로 하여 urease표면이 음전하를 갖도록 하고, 전극에 0.6 V (vs. SCE(Saturated Calomel Electrode))의 일정 전압을 가함으로써 urease가 전도성 고분자 표면에 전기적으로 흡착되도록 하였다. 이상의 방법으로 제작한 요소 센서의 감도는 PPy와 P3MT를 전자 전달 매질로 사용한 경우, 각각 8.44 ${\mu}A/mM{\cdot}cm^2$와 1.55 ${\mu}A/mM{\cdot}cm^2$의 감도를 보였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.86-86
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• 2010

Micro- and nanoscale texturing and control of surface energy have been considered for superhydrophobicity on polymer and silicon. However these surfaces have been reported to be difficult to meet the robustness and transparency requirements for further applications, from self cleaning windows to biochip technology. Here we provided a novel method to fabricate a nearly superhydrophobic soda-lime glass using two-step method. The first step involved wet etching process to fabricate micro-sale patterns on soda-lime glass. The second step involved application of $SiO_x$-incorporated DLC to generate high intrinsic contact angle on the surface using chemical vapor deposition (CVD) process. To investigate the effect of surface roughness, we used both positive and negative micro-scale patterns on soda-limeglass, which is relatively hard for surface texturing in comparison to quartz or Pyrex glasses due to the presence of impurities, but cheaper. For all samples we tested the static wetting angle and transparency before and after 100 cycles of wear test using woolen steel. The surface morphology is observed using optical and scanning electron microscope (SEM). The results shows that negative patterns had a greater wear resistance while the hydrophobicity was best achieved using positive patterns having static contact angle up to 140 deg. with about 80% transparency. The overall experiment shows that positive patterns at etching time of 1 min shows the optimum transparency and hydrophobicity. The optimization of micro-scale pattern to achieve a robust, transparent, superhydrophobic soda-lime glass will be further investigated in the future works.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.229.2-229.2
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• 2013

Yttrium oxide (Y2O3)는 band gap이 5.5 eV 정도로 상대적으로 넓고, 굴절상수가 1.8, 유전율이 10~15, Silicon 과의 격자 불일치가 작은 특성을 가지고 있다. 또한 녹는점이 높아 열적으로 안정하기 때문에 전자소자 및 광학소자에 다양하게 응용되는 물질이다. Y2O3 박막은 다양한 방법으로 증착할 수 있는데, 그 방법에는 e-beam evaporation, laser ablation, sputtering, thermal oxidation, metal-organic chemical vapor deposition, and atomic layer deposition (ALD) 등이 있다. ALD는 기판 표면에 흡착된 원자들의 자기 제한적 반응에 의하여 박막이 증착되기 때문에 박막 두께조절이 용이하고 step coverage와 uniformity 측면에서 큰 장점이 있다. 이전에는 Y(thd)3 and Y(CH3Cp)3 와 같은 금속 전구체를 이용하여 ALD를 진행하여, 증착 속도가 낮고 defect이 많아 non-stoichiometric한 조성의 박막이 증착되는 문제점이 있었다. 이번 연구에서는, (iPrCp)2Y(iPr-amd)와 탈이온수를 사용하여 Y2O3 박막을 증착하였다. Y2O3 박막 증착에 사용한 Y 전구체는 상온에서 액체이고 $192^{\circ}C$ 에서 1 Torr의 높은 증기압을 갖는다. Y2O3 박막 증착을 위하여 Y 전구체는 $150^{\circ}C$ 로 가열하여 N2 gas를 이용하여 bubbling 방식으로 공정 챔버 내로 공급하였다. Y2O3 박막의 ALD window는 $250{\sim}350^{\circ}C$ 였으며, Y 전구체의 공급시간이 5초에 다다르자 더 이상 증착 두께가 증가하지 않는 자기 제한적 반응을 확인할 수 있었다. 그리고 증착된 Y2O3 박막의 특성 분석을 위해 Atomic force microscopy (AFM)과 X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) 를 진행하였다. 박막의 Surface morphology 는 매끄럽고 uniform 하였으며, 특히 고체 금속 전구체를 사용했을 때와 비교하여 수산화물이 거의 없는 박막을 얻을 수 있었다. 그리고 조성 분석을 통해 증착된 Y2O3 박막이 stoichiometric하다는 것을 알수 있었다. 또한 metal-insulator-metal (MIM) 구조 (Ru/Y2O3/Ru) 의 resistor 소자를 형성하여 저항 스위칭 특성을 확인하였다.

• Current Photovoltaic Research
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• v.7 no.1
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• pp.9-14
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• 2019

Carrier selective solar cell structure has allured curiosity of photovoltaic researchers due to the use of wide band gap transition metal oxide (TMO). Distinctive p/n-type character, broad range of work functions (2 to 7 eV) and risk free fabrication of TMO has evolved new concept of heterojunction intrinsic thin layer (HIT) solar cell employing carrier selective layers such as $MoO_x$, $WO_x$, $V_2O_5$ and $TiO_2$ replacing the doped a-Si layers on either front side or back side. The p/n-doped hydrogenated amorphous silicon (a-Si:H) layers are deposited by Plasma-Enhanced Chemical Vapor Deposition (PECVD), which includes the flammable and toxic boron/phosphorous gas precursors. Due to this, carrier selective TMO is gaining popularity as analternative risk-free material in place of conventional a-Si:H. In this work hole selective materials such as $MoO_x$, $WO_x$ and $V_2O_5$has been investigated. Recently $MoO_x$, $WO_x$ & $V_2O_5$ hetero-structures showed conversion efficiency of 22.5%, 12.6% & 15.7% respectively at temperature below $200^{\circ}C$. In this work a concise review on few important aspects of the hole selective material solar cell such as historical developments, device structure, fabrication, factors effecting cell performance and dependency on temperature has been reported.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.2
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• pp.100-103
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• 2019

The change in vanadium amount according to the growth direction of vanadium-doped semi-insulated (SI) SiC single crystals using high-purity SiC powder was investigated. High-purity SiC powder and a porous graphite (PG) inner crucible were placed on opposite sides of SiC seed crystals. SI SiC crystals were grown on 2 inch 6H-SiC Si-face seeds at a temperature of $2,300^{\circ}C$ and growth pressure of 10~30 mbar of argon atmosphere, using the physical vapor transport (PVT) method. The sliced SiC single crystals were polished using diamond slurry. We analyzed the polytype and quality of the SiC crystals using high-resolution X-ray diffraction (XRD) and Raman spectroscopy. The resistivity of the SI SiC crystals was analyzed using contactless resistivity mapping (COREMA) measurements.

• Composites Research
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• v.35 no.3
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• pp.161-174
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• 2022

SiC fiber-reinforced SiC matrix composite is a promising accident-tolerant fuel cladding material to improve the safety of light water nuclear reactors. Compared to the current zirconium alloy fuel cladding as well as metallic accident-tolerant fuel cladding, SiC composite fuel cladding has exceptional accident-tolerance such as excellent structural integrity and extremely low corrosion rate during severe accident of light water nuclear reactors, which reduces reactor core temperature and delays core degradation processes. In this paper, we introduce the concept, technical issues, and properties of SiC composite accident-tolerant fuel cladding during operation and accident scenarios of light water nuclear reactors.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.06a
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• pp.72-72
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• 2001

Plasma polymerized thin films have been deposited on Si(lOO) substrates at $25-400^{\circ}C$ using thiophene ($C_4H_4S$) precursor by plasma assisted chemical vapor deposition (PACVD) method for low-dielectric device application. In order to compare physical properties of the as-grown thin films, the effects of the plasma power, gas flow ratio and deposition temperature on the dielectric constant and thermal stability were mainly studied. XRD and TED studies revealed that the as-grown thin films have highly oriented amorphous polymer structure. XPS data showed that the polymerized thin films that grown under different RF power and deposition temperature as well as different gas ratio of $Ar:H_2$ have different stoichiometric ratio of C and S compared with that of monomer, indicating a formation of mixture polymers. Moreover, we also realized that oxygen free and thermally stable polymer thin films could be grown at even $400^{\circ}C$. The results of SEM, AFM and TEM showed that the polymer films with smooth surface and sharp interface could be grown under various deposition conditions. From the electrical property measurements such as I-V and C-V characteristics, the minimum dielectric constant and the best leakage current were obtained to be about 3.22 and $10-11{\;}A/\textrm{cm}^2$, respectively.

• 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.