• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.281-281
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• 2010

Very low refractive index (<1.4) materials have been proved to be the key factor improving the performance of various optical components, such as reflectors, filters, photonic crystals, LEDs, and solar cell. Highly porous SiO2 are logically designed for ultralow refractive index materials because of the direct relation between porosity and index of refraction. Among them, ordered macroporous SiO2 is of potential material since their theoretically low refractive index ~1.10. However, in the conventional synthesis of ordered macroporous SiO2, the time required for the crystallization of organic nanoparticles, such as polystyrene (PS), from colloidal solution into well ordered template is typical long (several days for 1 cm substrate) due to the low interaction between particles and particle - substrate. In this study, polystyrene - polyacrylic acid (PS-AA) nanoparticles synthesized by miniemulsion polymerization method have hydrophilic polyacrylic acid tails on the surface of particles which increase the interaction between particle and with substrate giving rise to the formation of PS-AA film by simply spin - coating method. Less ordered with controlled thickness films of PS-AA on silicon wafer were successfully fabricated by changing the spinning speed or concentration of colloidal solution, as confirmed by FE-SEM. Based on these template films, a series of macroporous SiO2 films whose thicknesses varied from 300nm to ~1000nm were fabricated either by conventional sol - gel infiltration or gas phase deposition followed by thermal removal of organic template. Formations of SiO2 films consist of interconnected air balls with size ~100 nm were confirmed by FE-SEM and TEM. These highly porous SiO2 show very low refractive indices (<1.18) over a wide range of wavelength (from 200 to 1000nm) as shown by SE measurement. Refraction indices of SiO2 films at 633nm reported here are of ~1.10 which, to our best knowledge, are among the lowest values having been announced.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.193-193
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• 2011

To obtain ceramic films, the sol-gel coating technique has been broadly used with heat treatment, but crack formation tend to occur during heat treatment in thick sol-gel films. We prepared PZT thin films by sol-gel method with single-step spin coating process. The PZT solution have been synthesized using lead acetate ($Pb(CH_3COO)_2$), zirconium acetylacetonate ($Zr(OC_3H_7^n)_4$), and titanium diisopropoxide bis(acetylacetonate) 75wt% in isopropanol ($Ti(OC_3H_7^i)_2(OC_3H_7^n)_2$) as starting materials and n-propanol was selected as a solvent. The poly(vynilpyrrolidone) (PVP) was added with 0, 0.25, 0.5, 0.75, and 1 molar ratios to control viscosity of solution. We investigated influence of the viscosity on thickness, microstructure, and electrical properties of final PZT films. Thermo-gravimetric analysis and differential scanning calorimeter (TGA/DSC) was carried out from room temperature to $800^{\circ}C$ in order to measure pyrolysis temperature. Structural characteristics were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Ferroelectric and dielectric properties were measured by RT66A (Radiant) and impedance analyzer (Agilent), respectively. The thicknesses of PZT films depended on incorporation of an excess amount of PVP. Finally, we obtained PZT films of good quality without crack formation via single-step spin coating.

• 한국재료학회지
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• 제14권12호
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• pp.876-884
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• 2004

This study was to investigate whether the bioactivity of the anodized and hydrothermally treated Ti-6Al-7Nb alloy were affected by the time of hydrothermal treatment. Anodizing was performed at current density 30 $mA/cm^2$ up to 300 V in electrolyte solutions containing $DL-{\alpha}-glycerophosphate$ disodium salt hydrate $(DL-{\alpha}-GP)$ and calcium acetate (CA). Hydrothermal treatment was done at $300^{\circ}C$ for 30 min, 1 hr, 2 hrs, and 4 hrs to produce a thin film layer of hydroxyapatite (HA). The bioactivity was evaluated from HA formation on the surfaces in a Hanks' solution with pH 7.4 at $36.5^{\circ}C$ for 10, 20, and 30 days. Anodic oxide films were porous with pore size of $1\sim4{\mu}m\;and\;3\sim4{\mu}m$ thickness. The anodic oxide films composed with strong anatase peak with presence of rutile peak, and showed the increase in intensity of anatase peak after hydrothermal treatment. It was shown that the intensity of anatase peak increased with increasing the time of hydrothermal treatment but was no difference in rutile peak. The corrosion voltage was the highest in the group of hydrothermal treatment for 2 hrs (Ecorr: -338.6 mV). The bioactivity in Hank's solution was accelerated with increasing the time of hydrothermal treatment.

• 한국표면공학회지
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• 제36권3호
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• pp.229-233
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• 2003

Boron-Carbon-Nitrogen (B-C-N) system is an attractive ternary material since it has not only an extremely high hardness but also a number of other prominent characteristics such as chemical inertness, elevated melting point, and low thermal expansion. In this paper, the corrosion behavior of B-C-N thin films in aqueous solution was investigated B-C-N films with different composition were deposited on a platinum plate by magnetron sputtering in the thickness range of 150-280 nm. In order to understand effect of pH of solutions, $BC_{2.\;4}N$ samples were immerged in 1M HCl, 1M NaCl, and 1M NaOH solution at 298k, respectively. BCN samples with different carbon contents were exposed to 1M NaOH solutions to investigate effect of chemical composition on corrosion resistance. Corrosion rates of samples were measured by ellipsometry, From results, optical constant of $BC_{2,\;4}N$ films was found to be $N_2=2.110-0.295i$. The corrosion rates of $Bi_{1.\;0}C_{2.\;4}N_{1.\;0}$ films were NaOH>NaCl>HCl in orders. With increasing carbon content in B-C-N films, the corrosion resistance of B-C-N films was enhanced. The lowest corrosion rate was obtained for $B_{1.\;0}C_{4.\;4}N_{1.\;9}$ film.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.117-117
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• 2008

In MIM capacitor, poly-Si bottom electrode is replaced with metal bottom electrode. Noble metals can be used as bottom electrodes of capacitors because they have high work function and remain conductive in highly oxidizing conditions. In addition, they are chemically very stable. Among novel metals, Ru (ruthenium) has been suggested as an alternative bottom electrode due to its excellent electrical performance, including a low leakage of current and compatibility to high dielectric constant materials. Chemical mechanical planarization (CMP) process has been suggested to planarize and isolate the bottom electrode. Even though there is a great need for development of Ru CMP slurry, few studies have been carried out due to noble properties of Ru against chemicals. In the organic chemistry literature, periodate ion ($IO_4^-$) is a well-known oxidant. It has been reported that sodium periodate ($NaIO_4$) can form $RuO_4$ from hydrated ruthenic oxide ($RuO_2{\cdot}nH_2O$). $NaIO_4$ exist as various species in an aqueous solution as a function of pH. Also, the removal mechanism of Ru depends on solution of pH. In this research, the static etch rate, passivation film thickness and wettability were measured as a function of slurry pH. The electrochemical analysis was investigated as a function of pH. To evaluate the effect of pH on polishing behavior, removal rate was investigated as a function of pH by using patterned and unpatterned wafers.

• 한국표면공학회지
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• 제50권5호
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• pp.366-372
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• 2017

Plasma electrolytic oxidation(PEO) has attracted attention as a surface treatment which has high wear resistance and corrosion resistance. PEO is generally considered as cost-effective, environmentally friendly and superior in terms of coating performance. Most of studies about the PEO processes have been applied to light metals such as Al and Mg. Because the strength of Al and Mg is weaker than that of steel, there is a limit to the application. In this study, PEO process was used to form oxide coatings on Hot dipped aluminized(HDA) steel and the characteristics of the coating film according to the PEO current density were studied. The morphology was observed by SEM and component was analyzed by using EDS. The corrosion behaviors of PEO coating films were estimated by exposing salt spray test at 5 wt.% NaCl solution and measuring polarization curves in deaerated 3 wt.% NaCl solution. With the increase of PEO process current density, the pore size of the coating surface and the thickness of coating increased. It was confirmed that no Fe component was present on the coating surface. PEO coating films obviously showed good corrosion resistance compared with HDA. It is considered that the PEO coating acts as a barrier to protect the base material from external factors causing corrosion.

• 한국식품과학회지
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• 제36권3호
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• pp.432-439
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• 2004

알긴산 필름의 수분저항 특성을 증진시키기 위하여 지방산 (lauric, palmitic, stearic, oleic acid)과 복합필름을 제조하고 $CaCl_{2}$용액으로 처리하고, 이들의 처리 효과를 필름의 두께, 표면색, 미세구조, 인장강도, 신장률, 투습도, 수분용해도 및 등온 흡습곡선을 측정하여 조사하였다. 알긴산 필름은 지방산과의 복합필름을 형성하거나 $CaCl_{2}$ 처리를 하므로 필름의 미세구조가 크게 변하였다. 필름의 인장강도는 사용한 지방산의 종류에 따라 25-70% 정도 감소하였으나, $CaCl_{2}$ 처리에 의해 1.5-2배 증가하였다. 필름의 신장률은 두 가지의 처리에 의해 모두 감소하였다. 투습도는 불포화 지방산인 oleic acid를 제외하고는 지방산과 복합필름을 제조하므로 유의적으로(p<0.05) 감소하였다. 수분용해도 역시 두 가지 처리에 의해 모두 감소하였는데, stearic acid의 경우는 두 가지 방법을 병용하여 사용하므로 수분용해도가 약 30배 정도까지 감소하였다. 모든 알긴산 필름의 등온흡습곡선은 전형적인 두 단계의 변화 양상을 나타냈으며, 그 전환점은 수분활성도 0.75의 범위였다. 등온흡습곡선과 단분자층 수분함량의 결과는 $CaCl_{2}$ 처리에 의해 필름의 친수성이 감소하였음을 나타냈다.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2011년도 임시총회 및 하계학술연구발표회
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• pp.7-8
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• 2011

Basically, the lattice mismatch between film and substrate can make those BiFeO3(BFO) films distorted with strain structure. BFO phase can be stabilized on LaAlO3(LAO) represents the example of a multiferroic with giant axial ratio. Its crystal structure is not strictly tetragonal, but tetragonal with a slight monoclinic distortion and related to the rotation of the oxygen octahedra. In this study, we show that phases with a tetragonal-like epitaxial BFO films can indeed be ferroelectric and also can be stabilized via epitaxial growth onto LAO. Recent reports on epitaxial BFO films show that the crystal structure changes from nearly rhombohedral ("R-like") to nearly tetragonal("T-like") at strains exceeding approximately -4.5%, with the "T-like" structure being characterized by a highly enhanced c/a ratio. While both the "R-like" and the "T-like" phases are monoclinic, our detailed x-ray diffraction results reveal asymmetry change from MA and MC type, respectively. By applying additional strain or by modifying the unit cell volume of the film by substituting Ba for Bi, the monoclinic distortion in the "T-like" MC phase is reduced, i.e. the system approaches a true tetragonal symmetry. There are two different M-H loops for $Bi_{1-x}Ba_xFeO_{3-{\delta}}$(BBFO) and BFO films on SrTiO3(STO) & LAO substrates. Along with the ferroelectric characterization, these magnetic data indicate that the BFO phase stabilized on LAO represents the first example of a multiferroic with giant axial ratio. However, there is a significant difference between this phase and other predicted ferroelectrics with a giant axial ratio: its crystal structure is not strictly tetragonal, but tetragonal with a slight monoclinic distortion. Therefore, in going from bulk to highly-strained films, a phase sequence of rhombohedral(R)-to-monoclinic ["R-like" MA-to-monoclinic, "T-like" MC-to-tetragonal (T)] is observed. This sequence is otherwise seen only near morphotropic phase boundaries in lead-based solid-solution perovskites (i.e. near a compositionally induced phase instability), where it can be controlled by electric field, temperature, or composition. Our results show that this evolution can occur in a lead-free, stoichiometric material and can be induced by stress alone. Those major results are summarized as follows ; 1) Ba-doping increases the unit cell volume, 2) BBFO on LAO can be fully strained up to x=0.08 as a strain limit (Fig. 1), 3) P(E) & M(H) properties can be tuned by the variation of composition, strain, and film thickness.

• 한국결정성장학회지
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• 제19권6호
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• pp.305-310
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• 2009

PMMA 입자의 표면에 양전하를 갖는 전해질 폴리머 PDDA와 음전하를 갖는TALH를 사용하여 $TiO_2$ 박막을 LBL 법에 의해 성공적으로 제조하였다. 수정진동자의 측정을 통해 TALH의 용액의 pH가 감소됨에 따라 TALH의 적층량이 늘어나고 PMMA의 입자 표면에 코팅된 (PDDA/TALH) 박막의 두께가 증가됨을 확인하였다. (PDDA/TALH)n의 순서에 의해 코팅된 PMMA 입자들은 bilayer 수의 변화에 따라 다양한 색 변화를 보여주었다. (PDDA/TALH) 박막의 bilayer 수(n)가 10과 20 일 경우에 $a^*$와 $b^*$의 값은 막이 코팅되지 않은 PMMA의 값보다 감소하였고 색 변화는 $a^*$, $b^*$ 색도도에서 각각 green과 blue 방향으로 이동하였다. 이후 n의 수가 30, 40으로 증가됨에 따라 $a^*$와 $b^*$의 값은 증가하였고 색의 변화는 red와 yellow 방향으로 각각 이동하였다. 최종적으로 $(PDDA/TALH)_{50}$ 박막이 코팅된 PMMA 입자들은 박막이 코팅되지 않은 PMMA 입자들과 거의 비슷한 $a^*$와 $b^*$의 값을 보여주었다.

• Applied Biological Chemistry
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• 제11권
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• pp.123-130
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• 1969

고구마의 장려품종(奬勵品種)인 충승 100호, 수원(水原) 118호(號), 수원(水原) 147호(號), 신미(千美), 신미(新美)의 오품종(五品種)에 대하여 저장성(貯藏性), 가공적성(加工適性) 및 새로운 가공식품(加工食品)으로서 고구마칩의 제조조건(製造條件)에 관한 실험을 하여 다음과 같은 결과(結果)를 얻었다. 1) 공시품종(供試品種) 중에서 냉해(冷害) 및 연부병(軟腐病)에 대한 저항성(抵抗性)을 보면, 천미(千美), 수원(水原) 147호(號)가 가장 컸고 기타 3품종(品種)은 비교적 적었다. 2) 고구마중의 수지함량(樹脂含量)과 polyphenol 함량(含量)은 품종(品種)에 따라 많은 차이(差異)가 있었다. 3) 고구마의 품종(品種)에 따라 색상(色相)이 다른 고구마칩을 제조(製造)할 수 있었고 튀김용 기름으로는 채종유(採種油)가 최적(最適)임 을 알았다. 4) 고구마칩 제조방법(製造方法)으로는 두께 $1{\sim}2mm$의 박편(薄片)을 $40^{\circ}C$의 0.25% 산성아황산(酸性亞黃酸) 소다 수용액에 $30{\circ}40$분 침지(浸漬)한 후 $150{\sim}160^{\circ}C$의 유용(油溶)에서 $2.5{\sim}3.5$분간(分間) deep frying 하는 것이 선명(鮮明)한 색과 적당한 texture의 고구마칩을 얻는데 최적조건(最適條件)임을 확인(確認)하였다. 5) 고구마칩의 포장재료(包裝材料)로서는 polyethylene-cellophane film 이 방습도(防濕度) 및 파열강도(破裂强度)에 있어서 가장 우수(優秀)함을 확인(確認)하였다.