• Polymer(Korea)
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• v.28 no.2
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• pp.103-110
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• 2004

The biodegradable poly($\varepsilon$-caprolactone) (PCL) microcapsules containing tocopherol were prepared by oil-in-water emulsion solvent evaporation method. The features of the microcapsules were investigated in the manufacturing conditions and degradation behaviors. The form and structural feature of the microcapsules were measured by scanning electron microscope and X-ray diffraction, respectively. The surface free energy of the microcapsules was executed using contact angle measurement. As a result, the microcapsules were more stable and spherical with poly(vinyl alcohol) given in a surfactant. The surface free energy and crystallinity of microcapsules were decreased with increasing the core concentration, and degradation of PCL was occurred after 21 days. The release behaviors were examined by Uv/vis. spectrophotometer. It was found that the release rate of the microcapsules was increased with increasing the stirring rate, due to the increased interface between microcapsules and release media.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.316-316
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• 2010

Thin films spin-coated from solvent solutions are characterized by solution parameters and spin-coating process. In this study, performance characteristics of polymer solar cells were investigated with changing solution parameters such as solvent and additives. The phase-separation between polymer and fullerene is needed to make the percolation pathway for better transportation of hole and electron in polymer solar cells. For this reason, cooperative effects of solvent mixtures adding additives with distinct solubility have been studied recently. In this study, chlorobezene, 1, 2-dichlorbenzene, and chloroform were used as solvent. 1, 8-diiodoctaned and 1, 8-octanedithiol were used as additives and were added into poly(3-hexylthiophene-2, 5-diyl)/[6, 6]-phenyl C61 butyric acid methyl ester (P3HT/PCBM) blends. Pre-patterned ITO glass was cleaned using ultrasonication in mixed solvent with ethyl alcohol, isopropyl alcohol and acetone. PEDOT:PSS was spin-coated on to the ITO substrate at 3000rpm and was baked at $120^{\circ}C$ for 10min on the hotplate. The prepared solution was spin-coated at 1000rpm and the spin-coated thin film was dried in the Petri dishes. Al electrode was deposited on the thin film by thermal evaporation. The devices were annealed at $120^{\circ}C$ for 30min. By adding 2.5 volume percent of additives into the chlorobenzene from that bulk heterojunction films consisting of P3HT/PCBM, the power efficiency (AM 1.5G conditions) was increased from 2.16% to 2.69% and 3.12% respectively. We have investigated the effect of additives in P3HT/PCBM blends and the film characteristics and the film characteristics including J-V characteristics, absorption, photoluminescence, X-ray diffraction, and atomic force microscopy to mainly depict the morphology control by doping additives.

• Electrical & Electronic Materials
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• v.9 no.7
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• pp.690-695
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• 1996

We have systematically investigated the characterization of V$_{2}$O$_{5}$ thin films as a counter electrode for lithium based complementary electrochromic devices. The V$_{2}$O$_{5}$ thin films were prepared by thermal vacuum evaporation with varing the substrate temperature and film thickness. In electrochromic devices for smart windows, the WO$_{3}$ thin films with 400-800 nm thickness require to be capable of reversibly injection 10-15 mC/cm$^{2}$ of lithium, which is readily accomplished charge-balanced switching in a V$_{2}$O$_{5}$ thin films with 100-150nm thick. The V$_{2}$O$_{5}$ thin films produces considerably small changes in optical modulation properties in the visible and near infrared region(500-1100 nm) compared to the amorphous WO$_{3}$ thin films on 10-15 mC/cm$^{2}$ of lithium injection and the V$_{2}$O$_{5}$ thin films can therefore act as a counter electrode to WO$_{3}$ in a lithium based complementary clectrochromic devices. After 10$^{5}$ coloration/bleaching switching time, the degradation does not occurs and the devices exhibit a stable optical modulation in V$_{2}$O$_{5}$ thin films. It has shown that the injected lithium ion amounts in crystalline V$_{2}$O$_{5}$ thin films with the same thickness is large by 3-5 mC/cm$^{2}$ of lithium compared to the amorphous thin films in the same driving conditions. Therefore, to optimize the device performance, it is necessary to choose an appropriate film thickness and crystallinity of V$_{2}$O$_{5}$ for amorphous WO$_{3}$ film thickness as a working electrode.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.11a
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• pp.35-35
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• 2001

agnesium Oxide (MgO) with a NaCI structure is well known to exhibit high secondary electron emission, excellent high temperature chemical stability, high thermal conductance and electrical insulating properties. For these reason MgO films have been widely used for a buffer layer of high $T_c$ superconducting and a protective layer for AC-plasma display panels to improve discharge characteristics and panel lifetime. Up to now MgO films have been synthesized by lE-beam evaporation, Molecular Beam Epitaxy (MBE) and Metalorganic Chemical Vapor Deposition (MOCVD), however there have been some limitations such as low film density and micro-cracks in films. Therefore magnetron sputtering process were emerged as predominant method to synthesis high density MgO films. In previous works, we designed and manufactured unbalanced magnetron source with high power density for the deposition of high quality MgO films. The magnetron discharges were sustained at the pressure of O.lmtorr with power density of $110W/\textrm{cm}^2$ and the maximum deposition rate was measured at $2.8\mu\textrm{m}/min$ for Cu films. In this study, the syntheses of MgO films were carried out by unbalanced magnetron sputtering with various $O_2$ partial pressure and specially target power densities, duty cycles and frequency using pulsed DC power supply. And also we investigated the plasma states with various $O_2$ partial pressure and pulsed DC conditions by Optical Emission Spectroscopy (OES). In order to confirm the relationships between plasma states and film properties such as microstructure and secondary electron emission coefficient were analyzed by X-Ray Diffraction(XRD), Transmission Electron Microscopy(TEM) and ${\gamma}-Focused$ Ion Beam (${\gamma}-FIB$).

• Progress in Superconductivity
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• v.10 no.1
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• pp.29-34
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• 2008

Magnesium diboride ($MgB_2$) is an inexpensive and simple superconductor. This material was first synthesized and its structure confirmed in 1953 but its superconducting properties were not discovered until 2001 when they caused great excitement. In this study, superconducting $MgB_2$ thin films on the r-$Al_{2}O_3$ substrates have been grown by the combination of radio frequency magnetron sputtering of B and thermal evaporation of Mg. The deposition conditions were varied by changing deposition rate. Before the co-deposition of Mg and B, the deposition rates of each element have been measured separately. The $MgB_2$ layers had 400nm in thickness and superconducting transition temperatures have been measured around $\sim$38.6K. Superconducting properties have been measured by PPMS, XRD, and SEM.

• Journal of the Korean Vacuum Society
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• v.21 no.6
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• pp.354-361
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• 2012

The organic memory device was made by the plasma polymerization method which was not the dry process but the wet process. The memory device consist of the styrene and MMA monomer as the insulating layer, MMA monomer as the tunneling layer and Au thin film as the memory layer which was fabricated by thermal evaporation method. The I-V characteristics of fabricated memory device got the hysteresis voltage of 27 V at 40/-40 V double sweep measuring conditions. At this time, the optimized structure was 7 nm of Au thin film as floating gate, 400 nm of styrene thin film as insulating layer and 30 nm of MMA thin film as tunneling layer. Therefore we got the charge trapping characteristics by the hysteresis voltage. From the paper, styrene indicated a good charge trapping characteristics better than MMA. In the future, we expect to make devices by using styrene thin film rather than Au thin film.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.123-123
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• 2003

탄소나노튜브는 지금까지의 많은 연구를 통해 다양한 분야에 대한 응용 가능성이 확인되었으며, 그 중에서도 특히 탄소나노튜브를 이용한 전계방출표시소자(carbon nanotube field emission display, CNT-FED)는 상용화를 눈앞에 두고 있는 상황이다. 본 연구에서는 탄소나 노튜브를 합성할 수 있는 여러 가지 방법 중에서 열화학기상증착법(thermal chemical vapor deposition, thermal CVD)을 이용하여 유리기판 위에 탄소나노튜브를 합성하였다. Electron beam evaporation으로 유리기판 위에 전극층으로 Cr을 150nm를 증착하고 연속하여 촉매층인 Invar(Fe-53%Ni-6%Co 합금)를 10nm의 두께로 형성하였다. 사진식각으로 Cr층을 line 패턴한 후 Cr line 내의 Invar층을 line 및 dot 패턴하였다. 나노튜브 합성을 위해 480-58$0^{\circ}C$까지 진공분위기 또는 질소 분위기에서 20분간 승온한 후 CO(150sccm)와 H$_2$(1200sccm)를 주입하여 20분간 성장시키고 질소 분위기에서 냉각시켰다. 성장된 탄소나노튜브는 SEM, TEM, Raman spectroscopy 등을 통하여 구조 및 형상분석을 하였다. 진공승온의 경우 탄소불순물인 a-C이 많은 양 증착 되었으며 탄소나노튜브는 온도에 따라 1-5$\mu\textrm{m}$의 두께로 성장하였으나, 질소분위기 승온의 경우는 a-C이 거의 증착되지 않았으며 나노튜브의 두께가 10-20$\mu\textrm{m}$였다. 본 연구에서는 diode구조를 갖는 탄소나노튜브 에미터의 수명예측을 위해 여러 가지 가속측정조건에서 전계방출 특성을 연구하였다. Anode와 cathode 간의 간격을 400$\mu\textrm{m}$로 유지한 diode 구조에 대해 $10^{-6}$ torr 이하의 진공에서 전계방출을 측정하였다. 100 line의 에미터를 60Hz의 주파수에서 1/100 duty로 구동하였으며, duty비 증가에 따라 pulse의 on-time을 고정하고 frequency를 변화시켰다. dc까지 duty비가 증가됨에 따라 방출전류의 양이 선형적으로 증가하였다. 전압을 일정하게 고정시키고 각 duty비에서 시간에 따라 방출전류를 측정한 결과 duty비가 높을수록 방출전류가 시간에 따라 급격히 감소하였다. 각 duty비에서 방출전류의 양이 1/2로 감소하는 시점을 에미터의 수명으로 볼 때 duty비 대 에미터 수명관계를 구해 높은 duty비에서 전계방출을 시킴으로써 실제의 구동조건인 낮은 duty비에서의 수명을 단시간에 예측할 수 있었다.

• Korean Journal of Optics and Photonics
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• v.3 no.2
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• pp.111-116
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• 1992

ZnS:Sm, F TFEL devices with double insulating layer are prepared by e-beam evaporation method. Electroluminescence and luminous efficiency of the device fabricated at various conditions are investigated. The main transitions on the emission spectra for ZnS:Sm, F TFEL device occur at$^4G_{5/2}\to^6H_{9/2}^4G_{5/2}\to^6H_{7/2}, \;^4G_{5/2}\to^6H_{5/2}\to$.Among them, the dominant spectral line and its corresponding transition occur at $^4G_{5/2}\to^6H_{9/2}$(650 nm) and results in an orange-red emission color. The optimum concentration and substrate temperature for the ZnS:Sm, F TFEL device are around 1 wt% and $200^{\circ}C$. Luminous efficiency for the device is the largest at optimum condition.

• Journal of Korean Society of Forest Science
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• v.102 no.1
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• pp.66-73
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• 2013

This study was conducted to determine the effects of rice hull cover on seed germination and tray types, soil types, shading conditions for seedling growth of Codonopsis pilosuala. We also examined the feasibility of cultivation of small seedlings transplanted in the Gyeonggi-do area for a month. Under control condition, the seed germination was 8% whereas it dramatically increased to 78% under rice hull cover treatment. Under the different conditions (tray types, soil types, and shading conditions), young seedlings showed the best quality without shading in TKS soil of 50 plug cell tray, with the growth characteristics of plant height (11.9 cm), number of leaves (71), leaf width (3.1 cm), leaf length (2.6 cm), and root length (14.3 cm). Seedling quality was the best without any shading in TKS+perlite, with the physiological characteristics of evaporation (3.9 $mmol{\cdot}m^{-2}s^{-1}$), carbon assimilation (9.1 ${\mu}mol{\cdot}m^{-2}s^{-1}$), and water use efficiency (2.2 ${\mu}mol{\cdot}m^{-2}s^{-1}$). Considering the economical, morphological, physiological and survival rate of the seedlings, it was an ideal method for transplanting seedlings in the field after they have been grown for 30-45 days in TKS and TKS+perlite of 200 plug cell tray in 0% or 30% shaded conditions. As the results of 5 months examination on the possibility to cultivate Codonopsis pilosuala in the Gyeonggi-do area, 88% to 96% of survival rate was observed with normal induced flowers. Therefore, cultivation of Codonopsis pilosuala was possible in the Gyeonggi-do area. While there were symptoms of etiolation and wilting under no shading condition, they did not appear in 30% and 70% shading conditions. Therefore, cultivation of Codonopsis pilosuala is considered to be necessary 30% or 70% shading.

• Korean Journal of Agricultural Science
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• v.18 no.2
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• pp.148-156
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• 1991

This study was carried out to investigate the storage conditions and methods required for commercialization of Jeung-Pyon. The storage characteristics of Jeung-Pyon were examined with Universal Testing Machine (UTM, Instron model 1000) for textural properties during storage of under the conditions such as sealing, nonsealing, and temperatures. The differences in storage characteristics on the different varieties and years of rices were not shown. When the Jeung-Pyon was lost it's quality as a commercial product, the measured value of UTM was increased as hardness 0.74Kg to 1.0Kg, gumminess 0.23Kg to 0.59Kg, chewiness 6Kg.mm to 18Kg.mm, but decreased in adhesiveness 0.65Kg.mm to 0.40Kg.mm, cohesiveness 0.61 to 0.34, springiness 41mm to 32mm. The nonsealed Jeung-Pyon was lost it's quality for storing at room temperature because of the case-hardening after 2 days. In the case of sealed Jeung-Pyon, the case-hardening phenomena by the evaporation of moisture was not occured, therefore it was a significant factor for an extension in sealed Jeung-Pyon. The shelf-life of sealed Jeung-Pyon was 20 days and 5 days respectively during storage at $-20^{\circ}C$ and $20^{\circ}C$. The sealed Jeung-Pyon stored at $5^{\circ}C$ was lost it's quality, in consideration of cold chain this temperature was suitable for retrogradation of starch. The Jeung-Pyon sealed with air and mosture proof packaging material stored at the accelerated condition as 92% R.H. and $35^{\circ}C$ lost it's quality within two or three days.