• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.115-115
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• 2011

Nano hybrid superlattices consisting of organic and inorganic components have great potential for creation of new types of functional material by utilizing the wide variety of properties which differ from their constituents. They provide the opportunity for developing new materials with new useful properties. Herein, we fabricated new type of organic-inorganic nano hybrid superlattice thin films by a sequential, self-limiting surface chemistry process known as molecular layer depostion (MLD) combined with atomic layer deposition (ALD). An organic layer was formed at $150^{\circ}C$ using MLD with repeated sequintial adsorption of Hydroquinone and Titanium tetrachloride. A $TiO_2$ inorganic nanolayer was deposited at the same temperature using ALD with alternating surface-saturating reactions of Titanium tetrachloride and water. Using UV-Vis spectroscopy, we confirmed visible light absorption by LMCT. And FTIR spectroscopy and XPS were employed to determine the chemical composition. Ellipsometry and TEM analysis were also used to confirm linear growth of the film versus number of MLD cycles at all same temperature. In addition, p-n junction diodes domonstrated in this study suggest that the film can be suitable for n-type semiconductors.

• 한국세라믹학회지
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• 제54권5호
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• pp.443-447
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• 2017

The initial reaction of hexachlorodisilane ($Si_2Cl_6$, HCDS) on amorphous silica ($SiO_2$) surface for atomic layer deposition was investigated using density functional theory. Two representative reaction sites on the amorphous $SiO_2$ surface for HCDS reaction, a surface hydroxyl and a two-membered ring, were considered. The reaction energy barrier for HCDS on both sites was higher than its adsorption energy, indicating that it would desorb from the surface rather than react with the surface. At high temperature range, some HCDSs can have kinetic energy high enough to overcome the reaction energy barrier. The HCDS reaction on top of the reacted HCDS was investigated to confirm its self-limiting characteristics.

• Korean Chemical Engineering Research
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• 제43권1호
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• pp.60-65
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• 2005

연속적 전기흡착 셀에서 활성탄소섬유 부직포 전극을 사용하여 U(VI) 함유 폐액을 처리하였다. 더 낮은 전위에서 U(VI)의 전기흡착 효율을 높이기 위하여 ACFs를 화학약품으로 표면처리하고 그의 세공구조 및 관능기의 변화를 조사하였으며 처리조건이 U(VI)의 흡착에 미치는 영향을 고찰하였다. 표면처리한 모든 ACFs의 비표면적은 감소하였다. 중성염 및 염기성 용액으로 처리한 ACFs의 산성관능기는 감소했지만 산성 용액으로 처리한 ACFs의 산성관능기는 증가하였다. 산성관능기는 U(VI)의 흡착을 차단하여 산성용액 처리 ACFs 전극은 처리하지 않은 ACFs 전극에 비하여 U(VI)의 흡착용량이 감소했다. 중성염과 염기성 용액으로 처리한 ACFs 전극은 흡착용량이 크게 증가하여 -0.3 V의 낮은 전위에서도 처리하지 않은 ACFs 전극의 -0.9 V에 상응하는 결과를 얻었다. 이러한 결과는 ACFs 표면의 산성관능기 감소에 의한 이온의 차단효과(Shielding effect)가 줄어들 뿐만 아니라 음전위 가용에 의한 전기이중층 내에서의 $OH^-$의 증가로 U(VI) 흡착이 효율적으로 진행되었기 때문이다.

• 대한화학회지
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• 제54권1호
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• pp.93-98
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• 2010

본 연구에서는 Urea와 산 처리로 질소 및 산소 관능기가 도입된 다중벽 탄소나노튜브를 각각 제조하였으며, 표면처리에 따른 전기이중층 커패시터 (EDLCs) 특성을 관찰하였다. XPS, zeta-potential, 및 BET 분석방법을 이용하여 구조특성을 확인하였으며, 전기화학적 특성은 1 M 황산용액의 전해질에서 각각 50 $mVs^{-1}$과 100 $mVs^{-1}$의 주사속도로 순환전류 전압곡선 특성 실험을 통해 고찰하였다. 실험 결과로부터 MWNTs의 질소 원소구성비가 늘어날수록 축전용량이 증가하는 것을 확인하였으며, Urea 처리된 MWNTs의 축전용량이 가장 높은 수치를 나타내었다. 이는 전극 표면과 전하 활성종 간의 젖음성이 증가하고, 표면 관능기의 밀도가 증가하기 때문인 것으로 사료된다.

• 한국표면공학회지
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• 제37권4호
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• pp.215-219
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• 2004

We fabricated protein chip plates coated with silane carboxylate. The silane compound was immobilized by hydrogen bond and/or other chemical bonds on the surface of the plate. The plates were then prepared by binding $Ni^{2+}$ to surfaces terminated with silane carboxylate groups. The carboxylic acid surface was generated by chemical oxidation of the terminal double-bond functions of the silane-deposited layer. The $Ni^{2+}$ ions on the surface reacted readily to His-tagged proteins. A significant increase in His-tagged protein adsorption was achieved on the surface terminated with silane carboxylate with longer alkyl chain, suggesting better availability of these protein chip plates for proteomic studies.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.210.1-210.1
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• 2014

The hexagonal boron nitride (h-BN) sheet, a 2D material like graphene sheet, is comprised of boron and nitrogen atoms. Similar to graphene, h-BN sheet has attractive mechanical properties while it has a wide band gap unlike graphene. Recently, many experimental groups studied the growth of single BN layer by chemical vapor deposition (CVD) method on the copper substrate. To study the initial stage of h-BN growth on the copper surface, we have performed density functional theory calculations. We investigate several adsorption sites of a boron or nitride atom on the Cu surfaces. Then, by increasing the number of adsorbed B and N atoms, we study formation behaviors of the BN flakes on the surface. Several types of BN flakes atoms such as triangular, linear, and hexagonal shapes are considered on the copper surface. We find that the formation of the BN flake in triangular shape is most favorable on the surface. On the basis of the theoretical results, we discuss the growth mechanism of h-BN layer on the copper surfaces in terms of its shapes in the initial stage of growth.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.91-91
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• 2012

We aim in synthesizing various functional thin films thinner than ~ 10 nm for environmental applications and photovoltaic devices. Atomic layer deposition is used for synthesizing inorganic thin films with a precise control of the film thickness. Several examples about application of our thin films for removing volatile organic compounds (VOC) will be highlighted, which are summarized in the below. 1) $TiO_2$ thin films prepared by ALD at low temperature ($<100^{\circ}C$) show high adsorption capacity for toluene. In combination with nanostructured templates, $TiO_2$ thin films can be used as building-block of high-performing VOC filter. 2) $TiO_2$ thin films on carbon fibers and nanodiamonds annealed at high temperatures are active for photocatalytic oxidation of VOCs, i.e. photocatalytic filter can be created by atomic layer deposition. 3) NiO can catalyze oxidation of toluene to $CO_2$ and $H_2O$ at $<300^{\circ}C$. $TiO_2$ thin films on NiO can reduce poisoning of NiO surfaces by reaction intermediates below $200^{\circ}C$. We also fabricated inverted organic solar cell based on ZnO electron collecting layers on ITO. $TiO_2$ thin films with a mean diameter less than 3 nm on ZnO can enhance photovoltaic performance by reducing electron-hole recombination on ZnO surfaces.

• 한국지하수토양환경학회지:지하수토양환경
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• 제26권5호
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• pp.20-28
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• 2021

Perfluorinated compounds(PFCs), an emerging environmental pollutant, are environmentally persistent and bioaccumulative organic compounds that possess a toxic impact on human health and ecosystems. PFCs are distributed widely in environment media including groundwater, surface water, soil and sediment. PFCs in contaminated solid can potentially leach into groundwater. Therefore, understanding PFCs partitioning between the aqueous phase and solid phase is important for the determination of their fate and transport in the environment. In this study, the sorption equilibrium batch and kinetic experiment of PFCs were carried out to estimated the sorption coefficient(K_d) and the fraction between aqueous-solid phase partition, respectively. Sorption branches of the PFDA(Perfluoro-n-decanoic acid), PFNA(Perfluoro-n-nonanoic acid), PFOA(Perfluoro-n-octanoic acid), PFOS(Perfluoro-1-octane sulfonic acid) and PFHxS(Perfluoro-1-hexane sulfonic acid) isotherms were nearly linear, and the estimated K_d was as follow: PFDA(1.50) > PFOS(1.49) > PFNA(0.81) > PFHxS(0.45) > PFOA(0.39). The sorption kinetics of PFDA, PFNA, PFOA, PFOS and PFHxS onto soil were described by a biexponential adsorption model, suggesting that a fast transport into the surface layer of soil, followed by two-step diffusion transport into the internal water and/or organic matter of soil. Shorter times(<20hr) were required to achieve equilibrium and fraction for adsorption on solid(F₁, F₂) increased with perfluorinated carbon chain length and sulfonate compounds in this study. Overall, our results suggested that not only the perfluorocarbon chain length, but also the terminal functional groups are important contributors to electrostatic and hydrophobic interactions between PFCs and soils, and organic matter in soils significantly affects adsorption maximum capacity than kinetic rate.

• 한국재료학회지
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• 제20권9호
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• pp.457-462
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• 2010

Adsorption of a water molecule on a Si (001) surface and its dissociation were studied using density functional theory to study the distribution of -OH fragments on the Si surface. The Si (001) surface was composed of Si dimers, which buckle in a zigzag pattern below the order-disorder transition temperature to reduce the surface energy. When a water molecule approached the Si surface, the O atom of the water molecule favored the down-buckled Si atom, and the H atom of the water molecule favored the up-buckled Si atom. This is explained by the attractions between the negatively charged O of the water and the positively charged down-buckled Si atom and between the positively charged H of the water and the negatively charged up-buckled Si atom. Following the adsorption of the first water molecule on the surface, a second water molecule adsorbed on either the inter-dimer or intra-dimer site of the Si dimer. The dipole-dipole interaction of the two adsorbed water molecules led to the formation of the water dimer, and the dissociation of the water molecules occurred easily below the order-disorder transition temperature. Therefore, the 1/2 monolayer of -OH on the water-terminated Si (001) surface shows a regular distribution. The results shed light on the atomic layer deposition process of alternate gate dielectric materials, such as $HfO_2$.

• Coupled systems mechanics
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• 제3권4호
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• pp.329-344
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• 2014

In this work, quantum molecular dynamics simulations (QMD) are preformed to study the hydrogen molecules in three types of carbon nanostructures, $C_{60}$ fullerene, (5,5) and (9,0) carbon nanotubes and graphene layers. Interactions between hydrogen and the nanostructures is of importance to understand hydrogen storage for the development of hydrogen economy. The QMD method overcomes the difficulties with empirical interatomic potentials to model the interaction among hydrogen and carbon atoms in the confined geometry. In QMD, the interatomic forces are calculated by solving the Schrodinger's equation with the density functional theory (DFT) formulation, and the positions of the atomic nucleus are calculated with the Newton's second law in accordance with the Born-Oppenheimer approximation. It is found that the number of hydrogen atoms that is less than 58 can be stored in the $C_{60}$ fullerene. With larger carbon fullerenes, more hydrogen may be stored. For hydrogen molecules passing though the fullerene, a particular orientation is required to obtain least energy barrier. For carbon nanotubes and graphene, adsorption may adhere hydrogen atoms to carbon atoms. In addition, hydrogen molecules can also be stored inside the nanotubes or between the adjacent layers in graphite, multi-layer graphene.