• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.6
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• pp.588-593
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• 2023

The advantage of OTFT technology is that large-area circuits can be manufactured on flexible substrates using a low-cost solution process such as inkjet printing. Compared to silicon-based inorganic semiconductor processes, the process temperature is lower and the process time is shorter, so it can be widely applied to fields that do not require high electron mobility. Materials that have utility as electrode materials include carbon that can be solution-processed, transparent carbon thin films, and metallic nanoparticles, etc. are being studied. Recently, a technology has been developed to facilitate charge injection by coating the surface of the Al electrode with solution-processable titanium oxide (TiOx), which can greatly improve the performance of OTFT. In order to commercialize OTFT technology, an appropriate method is to use a complementary circuit with excellent reliability and stability. For this, insulators and channel semiconductors using organic materials must have stability in the air. In this study, carbon-doped Mo (MoC) thin films were fabricated with different graphite target power densities via unbalanced magnetron sputtering (UBM). The influence of graphite target power density on the structural, surface area, physical, and electrical properties of MoC films was investigated. MoC thin films deposited by the unbalanced magnetron sputtering method exhibited a smooth and uniform surface. However, as the graphite target power density increased, the rms surface roughness of the MoC film increased, and the hardness and elastic modulus of the MoC thin film increased. Additionally, as the graphite target power density increased, the resistivity value of the MoC film increased. In the performance of an organic thin film transistor using a MoC gate electrode, the carrier mobility, threshold voltage, and drain current on/off ratio (I_on/I_off) showed 0.15 cm²/V·s, -5.6 V, and 7.5×10⁴, respectively.

• The Journal of Korean Medicine
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• v.31 no.1
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• pp.23-29
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• 2010

Objective: The aim of this prospective, case-controlled study was to assess the difference of the amount of tongue coating between halitosis and non-halitosis patients using a digital tongue diagnosis system (DTDS). Methods: Sixty-five patients complaining of oral malodor were recruited for the study. The level of volatile sulfur compounds (VSC) in the oral cavity of the patients was measured by a portable gas chromatography. All patients were then divided into two groups, the halitosis group ($H_2S{\geq}1.5ng$/10ml, or $CH_3SH{\geq}0.5ng$/10ml) and the non-halitosis group ($H_2S$<1.5ng/10ml and $CH_3SH$<0.5ng/10ml), according to the VSC level criteria published by Tonzetich. Tongue images of the two groups were acquired and analyzed by DTDS, followed by the analysis of the tongue coating scores. Results: The tongue coating scores of the halitosis group were significantly higher than of the non-halitosis group (P=0.033). Furthermore, the difference of the posterior tongue coating between the two groups was more significant (P=0.000). Conclusions: Halitosis patients were shown to have a thicker tongue coating than those in the non-halitosis group. Moreover, the posterior dorsum of the tongue should be observed more cautiously when dealing with halitosis patients. Also, the progress and state of the patient's symptom of halitosis as diagnosed objectively by the portable gas chromatography could also possibly be analyzed instead by the DTDS tongue coating score.

• Aerospace Engineering and Technology
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• v.12 no.1
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• pp.105-110
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• 2013

The gimbal expansion joint for the pipe line of a liquid rocket engine undergoes high pressure and cyclic rotational displacement loadings. In present study, the moment analyses and tests of the internal-type gimbal expansion joint for the engine were performed. The moment components due to spring stiffness, friction and lateral force were obtained using a analytic method and their sums at low and high pressures were compared with the test results. Also, applying a $MoS_2$ dry film lubricant to the pin of a external hinge expansion joint, it is tested that the galling of the pin was removed and the friction coefficient was decreased for low pressures.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.365.2-365.2
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• 2014

Nickel sulfide (NiS) has been utilized in optoelectronic applications, such as transformation-toughening agent for materials used in semiconductor applications, catalysts, and cathodic materials in rechargeable lithium batteries. Recently, high quality nickel sulfide thin films have been explored using ALD/CVD technique. Suitable precursors are needed to deposit thin films of inorganic materials. However, nickel sulfide precursors available for ALD/CVD process are very limited to nickel complexes with dithiocarbamate and alkanethiolate ligands. Therefore, it is essential to prepare novel nickel sulfide suitable for ALD/CVD precesses. Herein we report on the synthesis and characterization of new nickel sulfide complex with designed aminothiolate ligand. Furthermore thin films of NiS have been prepared on silicon oxide substrates by spin coating nickel precursor 10 wt% in THF. The novel complex has been characterized by means of 1H-NMR, elemental analysis, thermogravimetric analysis (TGA), X-ray Diffraction (XRD) and scanning electron microscope (SEM).

• Journal of Electrochemical Science and Technology
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• v.10 no.3
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• pp.335-343
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• 2019

In this study, $Sr_2Ni_{1.8}Mo_{0.2}O_{6-{\delta}}$ (SNM) with a double perovskite structure was investigated as an alternative anode for use in the $CH_4$ fuel in solid oxide fuel cells. SNM demonstrates a double perovskite phase over $600^{\circ}C$ and marginal crystallization at higher temperatures. The Ni nanoparticles were exsolved from the SNM anode during the fabrication process. As the SNM anode demonstrates poor electrochemical and electro-catalytic properties in the $H_2$ and $CH_4$ fuels, it was modified by applying a samarium-doped ceria (SDC) coating on its surface to improve the cell performance. As a result of this SDC modification, the cell performance improved from $39.4mW/cm^2$ to $117.7mW/cm^2$ in $H_2$ and from $15.9mW/cm^2$ to $66.6mW/cm^2$ in $CH_4$ at $850^{\circ}C$. The mixed ionic and electronic conductive property of the SDC provided electrochemical oxidation sites that are beyond the triple boundary phase sites in the SNM anode. In addition, the carbon deposition on the SDC thin layer was minimized due to the SDC's excellent oxygen ion conductivity.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.2
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• pp.108-113
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• 2013

Chalcopyrite material $CuInSe_2$ (CIS) is known to be a very prominent absorber layer for high efficiency thin film solar cells. Current interest in the photovoltaic industry is to identify and develop more suitable materials and processes for the fabrication of efficient and cost-effective solar cells. Various processes have been being tried for making a low cost CIS absorber layer, this study obtained the CIS nanoparticles using commercial powder of 6 mm pieces for low cost CIS absorber layer by high frequency ball milling and cryogenic milling. And the CIS absorber layer was prepared by paste coating using milled-CIS nanoparticles in glove box under inert atmosphere. The chalcopyrite $CuInSe_2$ thin films were successfully made after selenization at the substrate temperature of $550^{\circ}C$ in 30 min, CIS solar cell of Al/ZnO/CdS/CIS/Mo structure prepared under various deposition process such as evaporation, sputtering and chemical vapor deposition respectively. Finally, we achieved CIS nanoparticles solar cell of electric efficient 1.74 % of Voc 29 mV, Jsc 35 $mA/cm^2$ FF 17.2 %. The CIS nanoparticles-based absorber layers were characterized by using EDS, XRD and HRSEM.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.347.2-347.2
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• 2016

Recently, in order to improve the performance of the colloidal quantum dot solar cells (CQDSCs), various efforts such as the modification of the cell architecture and surface treatment for quantum dot (QD) passivation have been made. Especially, the incorporation of halides into the QD matrix was reported to improve the performances significantly via passivating QD trap states that lower the life-time of the minority-carrier. In this work, we fabricated a lead sulfide (PbS) QD bilayer treated with different ligands and utilized it as a photoactive layer of the CQDSCs. The bottom and top PbS layer was treated using metal iodide ($MI_x$ and butanedithiol (BuDT), respectively. All the depositions and ligand treatments were carried out in air using layer-by-layer spin-coating process. The fabrication of the active layers as well as the n-type zinc oxide (ZnO) layer was successfully carried out on the bendable indium-tin-oxide (ITO)-coated polyethylene terephthalate (PET) substrate, which implies that this technique can be applied to the fabrication of flexible and/or wearable solar cells. The power conversion efficiency (PCE) of the CQDSCs with the architecture of $PET/ITO/ZnO/PbS-MI_x/PbS-BuDT/MoO_x/Ag$ reached 4.2 %, which is significantly larger than that of the cells with single QD (PbS-BuDT) layer.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.145-146
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• 2015

초미세 가공 및 치수안정성 향상을 위한 다이아몬드 마이크로 블레이드의 DLC 코팅이 연삭 과정에서 결합구조가 안정적으로 유지되는지 알아보기 위해 Cu/Sn 금속 결합재에 $MoS_2$ 고체 윤활제를 첨가한 후 PAPVD법으로 DLC 박막을 블레이드의 측면에 증착하였다. 실착 절삭 시험을 위해 마이크로 블레이드 시편을 제조하여 충분한 드레싱 과정 후 절삭 시험을 행하였으며 라만 분광법을 통해 절삭 전후 DLC 코팅에 존재하는 $sp^2$, $sp^3$ 결합의 분율을 조사하고 그 결과를 토대로 DLC 코팅의 특성의 변화를 분석하였다. DLC 코팅에 존재하는 D밴드와 G밴드의 비인 ID/IG는 절삭 후 증가하는 경향을 보였으며 결과적으로 절삭 과정 중 흑연화가 진행되었음을 확인하였다.

• Journal of the Korean Ceramic Society
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• v.31 no.3
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• pp.321-329
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• 1994

Functionally gradient materials(FGM), which have the continuous or stepwise variation in a composition and microstructure, are being noticed as the material that solves problems caused by heterogeneous interface of coating or joining. And these materials also expect new functions occured by gradient composition itself. Therefore, to examine possibility of thermal barrier materials, TZP/Mo·FGM and TZP/Ni·FGM were fabricated by sintering method. As to the sintered specimens, sintering shrinkage, relative density and Vicker's hardness in each composition were examined. The phenomena due to the difference of sintering shrinkage velocity during sintering process and the thermal stress induced through differences of thermal expansion coefficient in FGM were discussed. And the structure changes at interface and microsturcture of FGM were investigated. As a results, the difference of shrinkage between ceramic and metal was about 14% in TZP/Mo and 7% in TZP/Ni. The relative density and hardness were considerably influenced by metal content changes. Owing to unbalance of sintering shrinkage velocity between ceramic and metal, various sintering defects were occured. To control these sintering defects and thermal stress, gradient composition of FGM should be narrow. The microstructure changes of FGM depended on the ceramic or metal volume percents and were analogous to the theoretical design.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 1999.10a
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• pp.3-4
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• 1999

최근 산업이 고속도화, 고능률화 및 고정멸화의 추세로 발전함에 따라 우수한 내마모성, 인성, 고온 안정성 및 내구성을 갖는 공구 및 금형을 요구하게 되었다. 그러나 이와같은 성질들은 어떤 단일 재료에서는 얻을 수 없으며 적당한 기판공구나 금혈위에 내마모성 보호피막을 coating함으로 비교적 저렴하게 얻을 수 있다. 화학증착법으로 TiC, TiN등을 증착시킬때에는 $1000^{\circ}C$정도의 반응온도가 필요하며 이러한 증착온도는 모재가 초경합금일때는 문제가 안되나 강재일 경우 모재의 연화와 칫수변화의 문제를 야기시킨다. 최근에는 플라즈마를 사용하여 증착반응온도를 $550^{\circ}C$ 이하로 낮추는 플라즈마 화학 증착볍(PACVD)이 대두되고 있다. 그러나 이 방법어서 는 뚱착하려는 금속원소가 TiCl4의 형태로 공급되고 있으므로 생성된 층이 염소를 포함하고 있다. 이 층에 잔존하는 염소는 층의 기계적 성질을 저하시키고 층내의 stress를 유발시킨다. 또한 HCI개스의 생성으로 인하여 펌프 및 장비의 부식이 촉진 된다 이러한 결점을 극복하기 위하여 금속유기화합물 전구체(metallo-organic precursor)로 $TiCl_4$를 대체하고자 하는 연구가 활발하게 진행되고 있으며 본 연구실에서 이에 대하여 연구한 결과를 소개하고자 한다. diethylamino titanium을 전구체로 사용하여 $H_2,\;N_2,\;Ar$분위기하에서 pulsed d.c.를 사용하는 MO-PACVD에 의하여 $150~250^{\circ}C$의 저온에서 Al 2024 기판에 TiCN층 형 성을 하였다. 전구체 증발온도는 $74~78^{\circ}C$의 온도범위어야 하며 고경도의 코탱층은 54% duty, 14.2kHz, 450V의 조건에서 얻어졌으며 duty, 주파수, 전압이 증가함에 따라 경도는 저하되었다. 이때의 표면 morphology를 SEM으로 조사한바 dome structure가 크게 발달되었음을 알 수 있었다. 본 실험의 온도 범위내에서 얻은 TiCN 증착반응의 활성화에너지는 7.5Kcal/mol이었다. 증착된 TiCN층은 우수한 내마모섣을 나타내었으며 스크래치테스트 결과 17N의 엄계하중을 나타내었다. 본 연구에서 변화 시킨 duty, 주파수, 전압의 범위에서는 층의 밀착력은 크게 변화하지 않았다. titanium isopropoxide를 전구체로 사용하여 Hz, Nz 분위기하에서 d.c.를 사용하는 MO-PACVD에 의하여 Ti(NCO) 코팅층을 SKDll, SKD61, SKH9 공구강에 형성시키는 공정을 개발하였다. 최적의 Ti(NCO) 코탱층을 얻기 위해 유입전구체 부피%의 양은 향착압력의 5%를 넘지 않아야 되고 수소와 젤소 가스비가 1:1일 때 가장 높은 코팅층의 경도값을 나타내었다. 수소와 질소 가스비가 3:7일 때 TiFeCr(NCO)의 복화합물 코팅층이 형성됨을 알 수 있었고 500t의 증착온도에서 얻은 Ti(NCO) 코팅층이 높은 경도값과 좋은 내식성을 나타내었다. 또한 이와같은 Ti(NCO) 코팅공정과 본 실험실에서 개발한 확산층만 형성시키는 plsma nitriding 공정을 결합하여 복합코탱층을 형성하였는데 이 복합코팅층은 고경도와 우수한 내마모성, 내식성 뿐만 아니라 10)N 이상의 뛰어난 밀착력을 나타내었다. 현재 많이 사용되고 있는 PVD법은 step coverage가 좋지 않은 점과 cost intensive p process라는 단점이 있다. MO-PACVD법은 이러한 문제를 해결할 수 있는 방법으로서 앞으로 지속적인 도전이 요구되는 분야이다.