• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(1)
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• pp.197-201
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• 1996

In the detail reaction-rate measurements in a critical assembly using the foil activation method, the measured activations of detector foils have inevitably errors caused by detector foil self-shielding effect. If neutron flux could be approximated to Westcott flux: i.e. well thermalized Maxwellian distribution, these activations of detector foil could be corrected to represent the unperturbated flux at any detected position in the cell with using Westcott option and reaction-rate option of the lattice code, WIMS-AECL. These calculated detector material self-shielding correction factors of the tested fuel, CANFLEX provided much information about neutron spectrum of test lattice cell as well as the correction factors themselves. The results could be verified by another lattice calculations.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.209.2-209.2
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• 2014

In recent years, researches about hydrophobic and hydrophilic surfaces have been executed however their other effects have not been researched enough. In this paper, the fabrication method of hierarchical structures of micro line array combined with fluorinated wax for anisotropic superomniphobic wettability is presented. We have achieved anisotropic and superomniphobic surface via simple two step methods, which are maskless photolithography and wax deposition. In order to prove how to provide those characteristics, SEM, contact angle measurement tool and X-ray diffraction are used. Fluorinated wax is crystalized self-assembly and it is subordinated on micro line array so that it is able to display anisotropic wettability. Understanding on anisotropic superomniphobic surface and simple fabrication method has been attracted to apply for lots of applications which range from self-cleaning surface, microfluidic chip, to directionally fluid control device, even in oily fluid.

• 한국분말재료학회지
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• 제16권6호
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• pp.410-415
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• 2009

Hexagonal barium ferrite ($BaFe_{12}O_{19}$) nano-particles have been successfully synthesised using selfassembly method. Diethyleneamine (DEA) surfactant was used to fabricate the micelle structure of Ba-DEA complex under various DEA concentrations. $BaFe_{12}O_{19}$ powders were synthesized with addition Fe ions to Ba-DEA complex and then heat treated at temperature range of 800-1000${\circ}C$. The molar ratio of Ba/DEA and heat-treatment temperature significantly affected the magnetic properties and morphology of $BaFe_{12}O_{19}$ powders. $BaFe_{12}O_{19}$ powders synthesized with Ba/DEA molar ratio of 1 and heat-treated at 1000${\circ}C$ for 1 hour showed the coercive forces (iHc) of 4.84 kOe with average crystal size of about 200 nm.

• 한국광학회:학술대회논문집
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• 한국광학회 2003년도 제14회 정기총회 및 03년 동계학술발표회
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• pp.14-15
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• 2003

광결정(photonic crystal)은 주기적인 유전율 차이를 가지고 있는 인공적인 광학 물질이다. 그래서 이러한 광결정을 지나가는 전자기파는 마치 반도체와 같은 밴드갭을 가지게 된다. 우리는 silica nanosphere를 사용해서 자연의 보석 중, opal과 유사한 3차원 fcc(face-centered cubic) structure를 가지는 광결정을 만들었다. 평평한 유리기판을 용액에 수직으로 담근 후, 용액을 상온에서 증발시키면 자기 조립 방법(self-assembly method)으로 광결정이 만들어진다. (중략)

• 전자공학회논문지SC
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• 제48권2호
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• pp.28-34
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• 2011

이전 보고에서 우리는 오직 포토리소그래피(photolithography) 공정만을 이용하여 단일벽 탄소 나노튜브 (single-walled carbon nanotube; SWCNT)를 산화막 (silicon-dioxide; $SiO_2$)이 형성된 실리콘 (silicon; Si) 기판위에 선택적으로 흡착시키는 공정 방법에 대해 조사했었다. 본 논문에서, 우리는 위에서 설명한 기법을 이용하여 단일벽 탄소 나노튜브 채널을 가진 전계효과 트랜지스터 (field emission transistor; FET)를 제작하였다. 또한, 제작된 단일벽 탄소 나노튜브 기반 전계효과 트랜지스터 소자의 게이트 전압에 따른 전류 전압특성이 조사되었다. 이 전계효과 트랜지스터는 센서로서 작동될 수 있다. 포토리소그래피 공정에 의해 열산화막이 형성된 실리콘 기판 표면위에 단일벽 탄소 나노튜브가 흡착될 부분(채널부분)의 포토레지스트가 노출되도록 포토레지스트 패턴이 형성된다. 이 포토레지스트 패턴이 형성된 기판은 단일벽 탄소 나노튜브가 분산된 다이클로로벤젠 (dichlorobenzene; DCB) 용액 속에 담가진다. 남아 있는 포토레지스트 패턴이 아세톤에 의해 제거 되면, 결과적으로 채널부분 (소오스와 드레인 전극사이) 에 선택적으로 단일벽 탄소 나노튜브 채널이 형성된다. 이 간단한 가기 조립 기술이 이용됨으로써 우리는 단일벽 탄소 나노튜브 채널을 가진 4개의 전계효과 트랜지스터 어레이를 성공적으로 제작하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.291-291
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• 2013

The wettability of TiO2 layers is controlled by forming highly ordered arrays of nanocones using nanopatterning, based on self-assembly and dry etching. Nanopatterning of TiO2 layers is achieved via formation of self-assembled monolayers of SiO2 spheres fabricated using the Langmuir-Blodgett technique, followed by dry etching. Compared to a thin film TiO2 layer, the nanopatterned TiO2 samples show a smaller static water contact angle, where the water contact angle decreases as the etching time increases, which is attributed to the Wenzel equation. When TiO2 layers are coated by 1H,1H,2H,2H-perfluorooctyltrichlorosilane, we observed the opposite behavior, exhibiting superhydrophobicity (up to contact angle of $155^{\circ}$) on the nanopatterned TiO2 layers. Self-assembled nanopatterning of the TiO2 layer may provide an advanced method for producing multifunctional transparent layers with self-cleaning properties.

• 한국재료학회지
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• 제17권1호
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• pp.31-36
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• 2007

Nanoimprint lithography (NIL) is a new lithographic method that offers a sub-10nm feature size, high throughput, and low cost. One of the most serious problems of NIL is the stiction between mold and resist. The antistiction layer coating is very effective to prevent this stiction and ensure the successful NIL results. In this paper, an antistiction layer was deposited by VSAM (vapor self assembly monolayer) method on silicon samples with FOTS (perfluoroctyltrichlorosilane) as a precursor for making an antistiction layer. A specially designed LPCVD (low pressure chemical vapor deposition) was used for this experiment. All experiments were achieved after removing the humidity. First, the evaporation test of FOTS was performed for checking the evaporation temperature at low pressure. FOTS was evaporated at 5 Tow and $110^{\circ}C$. In order to evaluate the temperature effect on antistiction layer, chamber temperature was changed from 50 to $170^{\circ}C$ with 0.1ml of FOTS for 1 minute. Good hydrophobicity of all samples was shown at about $110^{\circ}$ of contact angle and under $20^{\circ}$ of hysteresis. The surface energies of all samples calculated by Lewis acid/base theory was shown to be about 15mN/m. The deposited thicknesses of all samples measured by ellipsometry were almost 1nm that was similar value of the calculated molecular length. The surface roughness of all samples was not changed after deposition but the friction force showed relatively high values and deviations deposited at under $110^{\circ}$. Also the white circles were founded in LFM images under $110^{\circ}$. High friction forces were guessed based on this irregular deposition. The optimized VSAM process for FOTS was achieved at $170^{\circ}C$, 5 Torr for 1 hour. The hot embossing process with 4 inch Si mold was successfully achieved after VSAM deposition.

• 한국재료학회지
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• 제23권8호
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• pp.453-461
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• 2013

Controlling the stick and slip motions of the contact lines in a confined geometry comprised of a spherical lens with a flat substrate is useful for manufacturing polymer ring patterns. We used a sphere on a flat geometry, by which we could control the interfaces of the solution, vapor and substrate. By this method, hundreds of concentric ring-pattern formations of a linear conjugated polymer, poly [2-methoxy-5-(2-thylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), were generated with excellent regularity over large areas after complete solvent evaporation. Subsequently, the MEH-PPV ring patterns played a role as a directed template to organize highly regular concentric rings of single-walled carbon nanotubes(SWCNTs); when a droplet of the SWCNT suspension in water was casted onto the prepared substrate, hydrophobic polymer patterns confined the water dispersed SWCNTs in between the hydrophilicized $SiO_2/Si$ substrate. As the solvent evaporated, SWCNT-rings were formed in between MEH-PPV rings with controlled density. Finally, we used a lift-off process to produce SWCNT patterns by the removal of a sacrificial polymer template with organic solvent. We also fabricated a field effect transistor using self-assembled SWCNT networks on a $SiO_2/Si$ substrate.

• 한국재료학회지
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• 제24권12호
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• pp.715-719
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• 2014

(PDDA/$SiO_2$) thin films that consisted of positively charged poly (diallyldimethylammonium chloride) (PDDA) and negatively charged $SiO_2$ nanoparticles were fabricated on a glass substrate by an applying voltage layer-by-layer (LBL) self-assembly method. In this study, the microstructure and optical properties of the (PDDA/$SiO_2$) thin films coated on glass substrate were measured as a function of the applied voltage on the Pt electrodes. When 1.0 V was applied to a Pt electrode in a PDDA and $SiO_2$ solution, the thickness of the $(PDDA/SiO_2)_{10}$ thin film increased from 79 nm to 166 nm. The surface roughness also increased from 15.21 nm to 33.25 nm because the adsorption volume of the oppositely charged PDDA and $SiO_2$ solution increased. Especially, when the voltage was applied to the Pt electrode in the $SiO_2$ solution, the thickness increase of the (PDDA/$SiO_2$) thin film was larger than that obtained when using the PDDA solution. The refractive index of the fabricated (PDDA/$SiO_2$) thin film was ca. n = 1.31~1.32. The transmittance of the glass substrate coated by (PDDA/$SiO_2$)6 thin film with a thickness of 106 nm increased from ca. 91.37 to 95.74% in the visible range.

• 한국재료학회지
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• 제19권8호
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• pp.437-442
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• 2009

This paper describes an improved strategy for controlling the adhesion force using both the antiadhesion and adhesion layers for a successful large-area transfer process. An MPTMS (3-mercaptopropyltrimethoxysilane) monolayer as an adhesion layer for Au/Pd thin films was deposited on Si substrates by vapor self assembly monolayer (VSAM) method. Contact angle, surface energy, film thickness, friction force, and roughness were considered for finding the optimized conditions. The sputtered Au/Pd ($\sim$17 nm) layer on the PDMS stamp without the anti-adhesion layer showed poor transfer results due to the high adhesion between sputtered Au/Pd and PDMS. In order to reduce the adhesion between Au/Pd and PDMS, an anti-adhesion monolayer was coated on the PDMS stamp using FOTS (perfluorooctyltrichlorosilane) after $O_2$ plasma treatment. The transfer process with the anti-adhesion layer gave good transfer results over a large area (20 mm $\times$ 20 mm) without pattern loss or distortion. To investigate the applied pressure effect, the PDMS stamp was sandwiched after 90$^{\circ}$ rotation on the MPTMS-coated patterned Si substrate with 1-${\mu}m$ depth. The sputtered Au/Pd was transferred onto the contact area, making square metal patterns on the top of the patterned Si structures. Applying low pressure helped to remove voids and to make conformal contact; however, high pressure yielded irregular transfer results due to PDMS stamp deformation. One of key parameters to success of this transfer process is the controllability of the adhesion force between the stamp and the target substrate. This technique offers high reliability during the transfer process, which suggests a potential building method for future functional structures.