• Journal of the Microelectronics and Packaging Society
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• v.27 no.1
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• pp.25-29
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• 2020

This study demonstrates direct-patternable amorphous TiO_x resistive switching (RS) device and the fabrication method using photochemical metal-organic deposition (PMOD). For making photosensitive stock solutions, Ti(IV) 2-ethylhexanoate was used as starting precursor. Photochemical reaction by UV exposure was observed and analyzed by Fourier transform infrared spectroscopy and the reaction was completed within 10 minutes. Uniformly formed 20 nm thick amorphous TiO_x film was confirmed by atomic force microscopy. Amorphous TiO_x RS device, formed as 6 × 6 ㎛ square on 4 ㎛ width electrode, showed forming-less RS behavior in ±4 V and on/off ratio ≈ 20 at 0.1 V. This result shows PMOD process could be applied for low temperature processed ReRAM device and/or low cost, flexible memory device.

• Journal of the Korean Vacuum Society
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• v.15 no.4
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• pp.374-379
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• 2006

In this study, carbon nanotubes (CNTs) were grown on glass substrates coated with Ni/Cr by an atmospheric pressure plasma enhanced chemical vapor deposition(AP-PECVD) and their structural and electrical characteristics were investigated as a possible application to the field emitter of field emission display (FED) devices. The substrate temperature ($400{\sim}500^{\circ}C$) were varied and the grown CNTs were multi wall CNTs (at $500^{\circ}C$, 15 - 20 layers of graphene sheets, distance of each layer : 0.3nm, inner diameter: 10 - 15nm, outer diameter: 30 - 40nm). The ratio of defective carbon peak to graphite carbon peak of the CNTs grown at $500^{\circ}C$ (C measured by fourier transform(FT)-Raman was 0.772 $I_D / I_G$ ratio. When field emission properties were measured, the turn-on field was $2.92V/{\mu}m$ and the emission field at $1mA/cm^2$ was $5.325V /{\mu}m$.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.1
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• pp.185-194
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• 2012

Deepwater oil is becoming more attractive because most onshore and shallow water oil is developing or developed. With the on-going trend to deepwater oil developments, flow assurance problems which prevent oil flow from reservoir to processing facilities are becoming an issue because deposited material can be occurred in case oil is exposed to very different environment from reservoir. Wax deposition which is one of flow assurance problems can be a major technical and economic issue because it is very sensitive to temperature. In order to predict and mitigate wax problems, the precise measurement of wax appearance temperature (WAT) which is the starting temperature of wax precipitation is very important. Various methods have been suggested for WAT measurement of opaque oil because there is no standard method for opaque oil. In this study, the WAT of opaque oil samples was measured using viscosity measurement method, differential scanning calorimetry, filter plugging method, and pressurized filter plugging method. Wax deposition test and high temperature gas chromatography analysis were applied to verify measured WAT. As a result of study, the WAT of opaque oils was successfully measured and verified. If WAT measurement methods of opaque oil related to oil characteristics is systematized using the results of this study, it can be a valuable tool for WAT measurement of opaque oil and flow assurance related to wax deposition.

• Journal of the Korean institute of surface engineering
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• v.50 no.1
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• pp.35-41
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• 2017

$TiO_2$, $Al_2O_3$, and $TiO_2-Al_2O_3$ nanolaminated films were grown by atomic layer deposition (ALD) on the 316L stainless steel (SS316L) substrates at a temperature of $150^{\circ}C$. The growth kinetics of $ALD-TiO_2$ and $Al_2O_3$ thin films were systematically investigated in order to precisely control the thickness of each layers in the $TiO_2-Al_2O_3$ nanolaminated films using a high-resolution transmission electron microscopy. And, the exact deposition rates of $ALD-TiO_2$ on $Al_2O_3$ surface and $ALD-Al_2O_3$ on $TiO_2$ surface were revealed to be 0.0284 nm/cycle and 0.11 nm/cycle, respectively. At given growth conditions, the microstructures of $TiO_2$, $Al_2O_3$ and $TiO_2-Al_2O_3$ nanolaminated films were amorphous. The potentiodynamic polarization test revealed that the $TiO_2-Al_2O_3$ nanolaminated film coated SS316L had a best corrosion resistance, although all ALDcoated SS316L exhibited a clear improvement of the corrosion resistance compared with a bare SS316L.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.65-65
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• 2012

Copper zinc tin sulfide ($Cu_2ZnSnS_4$, CZTS) is a very promising material as a low cost absorber alternative to other chalcopyrite-type semiconductors based on Ga or In because of the abundant and economical elements. In addition, CZTS has a band-gap energy of 1.4~1.5eV and large absorption coefficient over ${\sim}10^4cm^{-1}$, which is similar to those of $Cu(In,Ga)Se_2$(CIGS) regarded as one of the most successful absorber materials for high efficient solar cell. Most previous works on the fabrication of CZTS thin films were based on the vacuum deposition such as thermal evaporation and RF magnetron sputtering. Although the vacuum deposition has been widely adopted, it is quite expensive and complicated. In this regard, the solution processes such as sol-gel method, nanocrystal dispersion and hybrid slurry method have been developed for easy and cost-effective fabrication of CZTS film. Among these methods, the hybrid slurry method is favorable to make high crystalline and dense absorber layer. However, this method has the demerit using the toxic and explosive hydrazine solvent, which has severe limitation for common use. With these considerations, it is highly desirable to develop a robust, easily scalable and relatively safe solution-based process for the fabrication of a high quality CZTS absorber layer. Here, we demonstrate the fabrication of a high quality CZTS absorber layer with a thickness of 1.5~2.0 ${\mu}m$ and micrometer-scaled grains using two different non-vacuum approaches. The first solution-processing approach includes air-stable non-toxic solvent-based inks in which the commercially available precursor nanoparticles are dispersed in ethanol. Our readily achievable air-stable precursor ink, without the involvement of complex particle synthesis, high toxic solvents, or organic additives, facilitates a convenient method to fabricate a high quality CZTS absorber layer with uniform surface composition and across the film depth when annealed at $530^{\circ}C$. The conversion efficiency and fill factor for the non-toxic ink based solar cells are 5.14% and 52.8%, respectively. The other method is based on the nanocrystal dispersions that are a key ingredient in the deposition of thermally annealed absorber layers. We report a facile synthetic method to produce phase-pure CZTS nanocrystals capped with less toxic and more easily removable ligands. The resulting CZTS nanoparticle dispersion enables us to fabricate uniform, crack-free absorber layer onto Mo-coated soda-lime glass at $500^{\circ}C$, which exhibits a robust and reproducible photovoltaic response. Our simple and less-toxic approach for the fabrication of CZTS layer, reported here, will be the first step in realizing the low-cost solution-processed CZTS solar cell with high efficiency.

• Journal of the Korean GEO-environmental Society
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• v.12 no.5
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• pp.51-57
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• 2011

Generally, ready-mixed concrete(RMC) gets hardened by time, so the remaining concrete in the drum should be cleaned. But if the RMC waste water generated from this is discharged to soil without any treatment, the strong alkaline elements and heavy metals affect water and ecosystem pollution. Although about 10 to 15% of water used for cleaning in the RMC factory is discharged to soil or river, the concrete report of this affecting soil pollution has not been sufficient. Hence, in this study it was analyzed the extraction of cleaning water from RMC factories all over the country and heavy metal and pH components remaining in soil when this is penetrated to various soils having water permeability. The specimens used for the experiment are weathering soil and soils having different particle size, and it is made to be penetrated to those for 24 hours while fixed thickness of the layer is maintained. Cleaning water is divided into that before deposition treatment(sludge water) and that after deposition treatment(upper water) to be penetrated into soil, and according to the result of penetrating sludge water to soil, Cu and Mn, Fe, and Zn were found to be remained over 23 to 90%. However, it is analyzed that in upper water having deposition treatment, Cu and Mn remain as 60% or more only in weathering soil.

• Journal of the Korean Ceramic Society
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• v.46 no.3
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• pp.301-305
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• 2009

The novel carbon coating process for interlayer of fiber reinforced ceramic composites between fiber and matrix was performed by carbonizing phenolic resin solution that coated on fiber surface in $N_2$ atmosphere at $600^{\circ}C$ to improve the strength and fracture toughness of CMC(ceramic matrix composite). 160 nm carbon layer was coated on fiber surface with 5 vol% of phenolic resin solution. Since the process temperature ($600^{\circ}C$) is lower than chemical vapor deposition($900{\sim}1000^{\circ}C$), the strength and toughness could be preserved. Furthermore the coating thickness uniformity was improved to 8% of deviation along the stacking sequence. Therefore, prevention from fiber degradation during coating process and controlling coating thickness uniformity along the preform depth were achieved by coating with phenolic resin carbonizing method.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.301-301
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• 2012

Amorphous In-Ga-Zn-O (a-IGZO)는 광학적으로 투명하고 높은 전자이동도를 가지고 있어서 차세대 thin-film-transistor의 channel layer 물질로 각광받고 있다. 이러한 a-IGZO를 TFT channel layer로 사용하기 위해서는 소스 드레인 전극물질과 IGZO박막의 계면에서 ohmic contact을 만드는 것도 중요하다. 하지만 산화물 반도체의 특성상 금속물질을 증착시킬 때 산화금속계면을 형성하기 때문에 ohmic contact이 형성되기 어려운 것으로 알려져 있다. Au는 보통 전극물질로 많이 사용되는데, 이는 전기전도도가 매우 높고, 독특한 산화환원반응 특성을 보이지만, 화학반응을 잘 일으키지 않는 안정성을 가지는 성질에 기인한다. 본 연구진은 Au가 a-IGZO에 증착 시에 일어나는 표면의 화학적 상태변화를 이해하기 위해 방사광을 이용한 고분해능 광전자 분광법을 이용하여 표면변화를 분석하였다. Au는 (Au 4f) 증착 초기엔 약간의 gold oxide가 함께 형성되지만, 주로 metal gold의 형태로 존재하였다. In 3d, Ga 3d, O 1s, Zn 3d 각각의 스펙트럼에서는 Au 증착으로 인해 낮은 결합에너지에 새로운 state가 나타났다. 한편, In은 상대적으로 다른 원소들에 비해 Au와 좀 더 결합을 잘 하는 것으로 나타났는데 이는, In 5s 전자궤도가 전도메커니즘에서 중요한 역할을 하기 때문에, In-Au의 상대적인 강한 결합은 a-IGZO의 전기적 특성 변화에 기여할 수 있음을 의미한다.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.773-776
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• 2005

In the fabrication of high performance Blue organic light emitting diode, 2-TNATA[4,4',4"-tris(2-naphthylphenyl-phenylamino)-triphenylamine] as hole injection material and NPB[N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine] as hole transport material were deposited on the ITO (Indium Tin Oxide)/Glass substrate by vacuum evaporation. And then, Blue color emission layer was deposited using GDI602 as a host material and GDI691 as a dopant. Finally, small molecule OLED with the structure of ITO/2-TNATA/NPB/GDI602+GDI691/Alq3/LiF/Al was obtained by in-situ deposition of Alq3, LiF and Al as electron transport material, electron injection material and cathode, respectively. Blue OLED fabricated in our experiments showed the color coordinate of CIE(0.14, 0.16) and the maximum luminescence efficiency of 1.06 lm/W at 11 V with the peak emission wavelength of 464 nm.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.237.2-237.2
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• 2016

A pure hafnium-carbide (HfC) coating layer was deposited onto carbon/carbon (C.C) composites using a vacuum plasma spray system. By adopting a SiC buffer layer, we successfully integrated C.C composites with a $100-{\mu}m-thick$ protective coating layer of HfC. Compared to the conventional chemical vapor deposition process, the HfC coating process by VPS showed increased growth rate, thickness, and hardness. The growth behavior and morphology of HfC coatings were investigated by FE-SEM, EDX, and XRD. From these results, it was shown that the addition of a SiC intermediate layer provided optimal surface conditions during the VPS procedure to enhance adhesion between C.C and HfC (without delamination). The thermal ablation test results shows that the HfC coating layer perfectly protected inner C.C layer from thermal ablation and oxidation. Consequently, we expect that this ultra-high temperature ceramic coating method, and the subsequent microstructure that it creates, can be widely applied to improve the thermal shock and oxidation resistance of materials under ultra-high temperature environments.