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- 저자 : Do-Heyoung (검색결과 37 건)
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송요순,김도형 전남대학교 촉매연구소 2001 觸媒硏究 論文集 Vol.22 No.-
Heterogeneous nucleation rate of water vapor on smooth surfaces, e. g. an immiscible liquid surface was investigated. The nucleation and growth of condensate nuclei could occur both by the direct addition of molecules from the vapor and from those adsorbed on the substrate. The vapor-condensate-substrate interfacial force, the critical supersaturation, number of adsorbed molecules were different ways of expressing the affinity between vapor molecules and substrate surface. We found that adsorbed molecules were usually far more important to the nucleation process than those in the vapor phase. The heterogeneous nucleation rate of water vapor on some liquid surfaces was studied also. The critical supersaturation was measured differently with interfacial tension. There were a little bit differences between Volmer theory and experimental values.
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Iron oxide grown by low-temperature atomic layer deposition
Do-Heyoung Kim,Seenivasan Selvaraj,Hee Moon,Ju-Young Yun 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.12
Atomic layer deposition (ALD) is a promising technology for fabricating conformal thin films of atomlevel thickness with chemical composition control over a variety of structures. This paper demonstrates the ALD of iron oxide thin films using a novel iron precursor, namely, bis[bis(trimethylsilyl)amide]iron [Fe(btmsa)2] and hydrogen peroxide as an oxygen source. The growth characteristics of iron oxide were investigated by varying the deposition temperatures from 100 to 225 oC, such that the ALD growth mode was observed at 150 to 175 oC with an average growth rate of 0.035±0.005 nm/cycle. The films deposited in ALD mode exhibited highly linear film thicknesses with the number of cycles and excellent conformality over high-aspect-ratio trenches. In addition, the deposited films were extremely pure and revealed a hematite phase without any subsequent heat treatment, even if the films were deposited at low temperatures.
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Nucleation and Film Growth of Chemically Vapor Deposited Tungsten on Various Types of TiN Glue Layer
Kim, Do-Heyoung,Song, Yo-Soon,Whang, Soon-Hong,Park, Jin-Won 전남대학교 촉매연구소 2001 觸媒硏究 論文集 Vol.22 No.-
The morphology and grain size of CVD W on MOCVD TiN films was investigated by varying the types of TiN glue layer. The morphology and grain size of W layer were found to be dependent upon the type of TiN glue layer adopted. W deposited on the non post-treated CVD-TiN exhibits lowest roughness levels with small grain size among the tested TDMAT-based TiN films. Also, the effects of rapid thermal annealing on the conformal properties of chemically vapor deposited W films were investigated with the contact-structure covered by TiN films. We found that out gassing from the TiN film is closely related with the step coverage of CVD W films. This out-gassing from TiN films was greatly reduced by the rapid thermal annealing of CVD TiN films at 650℃ for 30 sec in a N2 atmosphere, which increased step coverage of CVD W films to in excess of 90%, even at the relatively high W deposition temperature of 475℃.
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Kim, Do Heyoung,Kim, Byung Yup 한국화학공학회 2000 Korean Journal of Chemical Engineering Vol.17 No.4
Aluminum films were prepared on H₂-plasma pretreated TiN substrates at deposition temperatures of 60-250℃ by metallorganic chemical vapor deposition using dimethylethylamine alane as a precursor. The films were highly pure and the growth rates were 3-50 nm/min, where the lowest deposition temperature was 60℃. The resistivity was as low as 2.8 μΩcm. High substrate temperatures tended to favor a low resistivity and smooth surface morphology of the films, compared to films with a ow temperature at a given thickness. Numerous empty pores appeared in the A1 films deposited at a temperature below 150℃ when the film thickness exceeded 200 nm. The number of these pores tended to increase with decrease in temperature. However, in films deposited at temperatures above 200, there were no pores and the large grains were interconnected to a high degree. Higher deposition temperatures yielded a greater preference of the (111) orientation of Al films.
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Kim,Do Heyoung,Lee,Young J.,Pair,Chong Ook,Park,Jin Won,Kim,Jae Jeong 대한전자공학회 1995 ICVC : International Conference on VLSI and CAD Vol.4 No.1
In this paper, the nucleation and film growth of copper on TiN chemically treated with WF_6 and air-exposed TiN by chemical vapor deposition(CVD) from hexafluoroacetylacetonate copped trimethylvinylsilane, (NFA)Cu(TMVS), was studied. Copper grows as islands of poorly connected grains on air-exposed TiN. In contrast, copper grows as a continuous film with well-connected grains on the surface of WF_6-treated TiN. The role of the TiN surface condition has been examined using Auger electron spectroscopy(AES), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy(SEM).
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Kumbhar, Vijay S.,Kim, Do-Heyoung Elsevier 2018 ELECTROCHIMICA ACTA Vol.271 No.-
<P><B>Abstract</B></P> <P>The design of heterostructured pseudo-capacitive materials plays a key role in fabricating asymmetric supercapacitors (ASCs) with high energy density and electrochemical cycle life for the evolution of next-generation energy storage devices. Use of ZnCo<SUB>2</SUB>O<SUB>4</SUB> nanoflakes covered with MnO<SUB>2</SUB> nanosheets led to a synergistic effect that produced a larger electroactive surface area for charge storage than that provided by bare ZnCo<SUB>2</SUB>O<SUB>4</SUB> nanoflakes or MnO<SUB>2</SUB> nanosheets. The ZnCo<SUB>2</SUB>O<SUB>4</SUB> nanoflakes served as the backbone for the growth of the MnO<SUB>2</SUB> nanosheets. The ZnCo<SUB>2</SUB>O<SUB>4</SUB>-MnO<SUB>2</SUB> heterostructure was synthesized on Ni foam using a combined binder-free electrodeposition and hydrothermal method. The electrode formed using this unique method showed a maximum specific capacitance of 2057 F g<SUP>−1</SUP> at a current density of 1 A g<SUP>−1</SUP> with a rate capability of 65% even after a 15-fold increase in current density. Moreover, the electrode showed a cycling stability of 96.5% after 5000 successive cycles at a current density of 15 A g<SUP>−1</SUP>. An ASC formed using ZnCo<SUB>2</SUB>O<SUB>4</SUB>-MnO<SUB>2</SUB> as the positive electrode and activated carbon as the negative electrode delivered a maximum energy density of 69 W h kg<SUP>-1</SUP> with 93.5% capacity retention after 5000 cycles. Further, an experiment to investigate the commercial application of ASCs was conducted.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A MnO<SUB>2</SUB> nanosheets were coated on ZnCo<SUB>2</SUB>O<SUB>4</SUB> nanoflakes using a simple, eco-friendly, and low cost chemical methods. </LI> <LI> The ZnCo<SUB>2</SUB>O<SUB>4</SUB>-MnO<SUB>2</SUB> heterostructure exhibited a specific capacitance of 2057 F g<SUP>-1</SUP>. </LI> <LI> The ZnCo<SUB>2</SUB>O<SUB>4</SUB>-MnO<SUB>2</SUB> heterostructure exhibited a cycling stability of 96.5% after 5000 cycles. </LI> <LI> As-fabricated ZnCo<SUB>2</SUB>O<SUB>4</SUB>//activated carbon asymmetric supercapacitor (ASC) exhibited an energy density of 69 W h kg<SUP>-1</SUP>. </LI> <LI> Finally the demonstration of the as-prepared ASC confirmed the practical feasibility of the device. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Christwardana, Marcelinus,Kim, Do-Heyoung,Chung, Yongjin,Kwon, Yongchai Elsevier BV * North-Holland 2018 Applied Surface Science Vol.429 No.-
<P><B>Abstract</B></P> <P>A novel hybrid biocatalyst is synthesized by the enzyme composite consisting of silver nanoparticle (AgNP), naphthalene-thiol based couplers (Naph-SH) and glucose oxidase (GOx), which is then bonded with the supporter consisting of polyethyleneimine (PEI) and carbon nanotube (CNT) (CNT/PEI/AgNPs/Naph-SH/GOx) to facilitate glucose oxidation reaction (GOR). Here, the AgNPs play a role in obstructing denaturation of the GOx molecules from the supporter because of Ag-thiol bond, while the PEIs have the AgNPs keep their states without getting ionized by hydrogen peroxide produced during anodic reaction. The Naph-SHs also prevent ionization of the AgNP by forming self-assembled monolayer on their surface. Such roles of each component enable the catalyst to form (i) hydrophobic interaction between the GOx molecules and supporter and (ii) π-conjugated electron pathway between the GOx molecules and AgNP, promoting electron transfer. Catalytic nature of the catalyst is characterized by measuring catalytic activity and performance of enzymatic biofuel cell (EBC) using the catalyst. Regarding the catalytic activity, the catalyst leads to high electron transfer rate constant (9.6±0.4s<SUP>−1</SUP>), low Michaelis-Menten constant (0.51±0.04mM), and low charge transfer resistance (7.3Ωcm<SUP>2</SUP>) and high amount of immobilized GOx (54.6%), while regarding the EBC performance, high maximum power density (1.46±0.07mWcm<SUP>−2</SUP>) with superior long-term stability result are observed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CNT/PEI/AgNP/Naph-SH/GOx is suggested as anodic catalyst for the EBC. </LI> <LI> Catalytic activity and stability are enhanced due to AgNP and Naph-SH. </LI> <LI> Ag-thiol bonds obstruct denaturation of the GOx molecule. </LI> <LI> Naph-SH SAM promotes electron transfer and reduces charge transfer resistance. </LI> <LI> EBC including CNT/PEI/AgNP/Naph-SH/GOx shows high power density. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Atomic layer deposition of TiO2 from tetrakis-dimethylamido-titanium and ozone
Yong-Wan Kim,Do-Heyoung Kim 한국화학공학회 2012 Korean Journal of Chemical Engineering Vol.29 No.7
Ozone (O3) was employed as an oxygen source for the atomic layer deposition (ALD) of titanium dioxide (TiO2) based on tetrakis-dimethyl-amido titanium (TDMAT). The effects of deposition temperature and O3 feeding time on the film growth kinetics and physical/chemical properties of the TiO2 films were investigated. Film growth was possible at as low as 75 oC, and the growth rate (thickness/cycles) of TiO2 was minimally affected by varying the temperatures at 150-225 oC. Moreover, saturated growth behavior on the O3 feeding time was observed at longer than 0.5 s. Higher temperatures tend to provide films with lower levels of carbon impurities. The film thickness increased linearly as the number of cycles increased. With thicker films and at higher deposition temperatures, surface roughening tended to increase. The as-deposited films were amorphous regardless of the substrate temperatures and there was no change of crystal phase even after annealing at temperatures of 400-600 oC. The films deposited in 0.5 mm holes with an aspect ratio of 3 : 1 showed an excellent conformality.
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Roh, Sung-Hee,Cheong, Hyeonsook,Kim, Do-Heyoung,Woo, Hee-Gweon,Lee, Byeong-Gweon,Yang, Kap-Seung,Kim, Bo-Hye,Sohn, Honglae American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.1
<P>The generation of silver nanoparticle/bis(o-phenolpropyl)silicone composites have been facilitated by the addition of sodium tetrachloroaurate or gold(Ill) chloride (< 1 wt% of NaAuCl4 or AuCl3) to the reaction of silver nitrate (AgNO3) with bis(o-phenolpropyl)silicone [BPPS, (o-phenolpropyl)2(SiMe2O)n, n = 2,3,8,236]. TEM and FE-SEM data showed that the silver nanoparticles having the size of < 20 nm are well dispersed throughout the BPPS silicone matrix in the composites. XRD patterns are consistent with those for polycrystalline silver. The size of silver nanoparticles augmented with increasing the relative molar concentration of AgNO3 added with respect to BPPS. The addition of gold complexes (1-3 wt%) did not affect the size distribution of silver nanoparticles appreciably. In the absence of BPPS, the macroscopic precipitation of silver by agglomeration, indicating that BPPS is necessary to stabilize the silver nanoparticles surrounded by coordination.</P>
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