• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1229-1231
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• 1997

In this work, PZT(20/80)/(80/20) heterolayered thin film that has the tetragonal and rhombohedral structure was fabricated by Sol-Gel method spin-coated on the Pt/Ti/$SiO_2$/Si substrate by turns. The thickness of PZT-1 film obtained by six-times of drying/sintering process was about 480[nm]. This procedure was repeated several times to form PZT heterolayered thim film. PZT-5 thin films with top layer of tetragonal PZT(20/80) thin film showed dense grain structure and PZT-6 thin film with top layer of rhombohedral PZT(80/20) thin film showed the microstructure without rosette. Dielectric constant increased with increasing the number of coatings, and it was about 13S5 at PZT-6 thin film. Dielectric loss was not depend on the number of coatings.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1418-1419
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• 2006

PZT(80/20) powder was prepared by a sol-gel method and PZT thick films were fabricated by the screen-printing method on the alumina substrates. The coating and drying procedure was repeated 4 times. And then the PZT(20/80) precursor solution was spin-coated on the multilayered thick films. A concentration of a coating solution was 0.5 mol/L and the number of coating was repeated from 0 to 6. The porosity of the thick films was decreased with increasing the number of coatings and the PZT thick films with 6-times coated showed the dense microstructure and thickness of about 60-65 ${\mu}m$. All PZT thick films showed the typical XRD patterns of a typical perovskite polycrystalline structure. The relative dielectric constant and the dielectric loss of the PZT-6 thick film were 275 and 3.5, respectively. And the PZT-6 film shows the remanent polarization of 22.1 $C/cm^2$ and coercive field of 13.7 kV/cm.

• Macromolecular Research
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• v.16 no.2
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• pp.103-107
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• 2008

Carbon nanodots were prepared by the pyrolysis of a triblock copolymer. The triblock copolymer, poly(methyl methacrylate)-b-polystyrene-b-poly(methyl methacrylate) was synthesized by atom transfer radical polymerization using an initiator containing a diacetylene group. A polymer thin film on a mica substrate was prepared by spin-casting at 2,000 rpm from a 0.5 wt% toluene solution of the triblock copolymer. After drying, the cast film was vacuum-annealed for 48 h at $160^{\circ}C$. The annealed film formed a spherical morphology of polystyrene domains with a diameter of approximately 30 nm. The film was exposed to UV irradiation to induce a cross-linking reaction between diacetylene groups. In the subsequent pyrolysis at $800^{\circ}C$, the cross-linked polystyrene spheres were carbonized and the poly(methyl methacrylate) matrix was eliminated, resulting in carbon nanodots deposited on a substrate with a diameter of approximately 5 mn.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.809-812
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• 2004

(Pb,Sr)TiO3 (PST) thin films were fabricated by using the alkoxide-based sol-gel method. The PST stock solution was made and then spin-coated onto a PUTi/SiO2/Si substrate. The coating and drying procedures were repeated several times, and the PST thin films were sintered at 450-650 C for 1 h. All PST thin films showed dense and homogeneous structures without the presence of any rosette structure. The thicknesses of the PST thin films were approximately 200 nm. The dielectric constant and the dielectric loss of the PST thin films sintered at 550 C were about 404 and 0.0023, respectively. The leakage current density of the PST thin film sintered at 550 C was 3.13 x 10-8 A/cm2 at 1 V.

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.10
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• pp.1454-1459
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• 2012

An improved detection of radiation-induced paramagnetic faults was developed to identify the irradiation status of basil and clove. The effectiveness of different sample pretreatments, including freeze-drying (FD), oven-drying (OD), alcoholic-extraction (AE), and water-washing and alcoholic-extraction (WAE), were examined. All non-irradiated samples showed a single central signal ($g_0$=2.006), whereas radicals representing two additional side peaks ($g_1$=2.023 and $g_2$=1.986) with a mutual distance of 6 mT were detected in the irradiated samples. AE and WAE produced the best results for irradiated clove in terms of intensities of radiation-specific ESR signals and their ratios to the central signal. However, FD provided the highest intensities of radiation-specific ESR signals for basil, whereas their ratios to the major signal were better in the cases of AE and WAE. Signal noise, particularly due to $Mn^{2+}$ signals, was observed, whereas it decreased in AE and WAE pretreatments. Based on our results, AE and WAE can improve the detection conditions for radiation-specific ESR signals in irradiated samples.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.416-416
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• 2016

Organic-inorganic metal halide perovskite solar cells have received attention because it has a number of advantages with excellent light harvesting, high carrier mobility, and facile solution processability and also recorded recently power conversion efficiency (PCEs) of over 20%. The major issue on perovskite solar cells have been reached the limit of small area laboratory scale devices produced using fabrication techniques such as spin coating and physical vapor deposition which are incompatible with low-cost and large area fabrication of perovskite solar cells using printing and coating techniques. To solution these problems, we have investigated the feasibility of achieving fully printable perovskite solar cells by the blade-coating technique. The blade-coating fabrication has been widely used to fabricate organic solar cells (OSCs) and is proven to be a simple, environment-friendly, and low-cost method for the solution-processed photovoltaic. Moreover, the film morphology control in the blade-coating method is much easier than the spray coating and roll-to-roll printing; high-quality photoactive layers with controllable thickness can be performed by using a precisely polished blade with low surface roughness and coating gap control between blade and coating substrate[1]. In order to fabricate perovskite devices with good efficiency, one of the main factors in printed electronic processing is the fabrication of thin films with controlled morphology, high surface coverage and minimum pinholes for high performance, printed thin film perovskite solar cells. Charge dissociation efficiency, charge transport and diffusion length of charge species are dependent on the crystallinity of the film [2]. We fabricated the printed perovskite solar cells with large area and flexible by the bar-coating. The morphology of printed film could be closely related with the condition of the bar-coating technique such as coating speed, concentration and amount of solution, drying condition, and suitable film thickness was also studied by using the optical analysis with SEM. Electrical performance of printed devices is gives hysteresis and efficiency distribution.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.284-284
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• 2009

We have fabricated semiconductor nanocrystals using phase separation on flexible substrates for future application in QD-LEDs. The phase separation between the CdSe semiconductor nanocrystals and TPD organic underlayer can occur during the solvent drying, and the CdSe may rise towards the surface of the coated films, which is arranged into close packed array called self-assembly process. In this work, the polyethylene naphthalate (PEN) films of $200{\mu}m$ thickness was used as a flexible substrate, which was coated with indium tin oxide(ITO) as a transparent electrode of <$15{\Omega}/cm^2$. A number of solvents such as chloroform, toluene, and hexane was used and their coating properties were investigated using the spin coating process. The dispersion of both QD and TPD was rather poor in toluene and hexane and resulted in rougher surface and some aggregates. Meanwhile, the surface roughness of templates can be a very critical issue in the fabrication of QD-LED devices. Some experiments was performed to reduce the ~4nm surface roughness of the PEN films and It can be decreased to the minimum of ~0.7nm. Also discussed are the optical properties of semiconductor nanocrystals used in this phase separation and possible large area and continuous coating process for future application.

• Journal of Food Hygiene and Safety
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• v.15 no.3
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• pp.248-251
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• 2000

Electron spin resonance (ESR) spectroscopy was used to detect irradiated chicken eggs, to investigate the effect of irradiation dose on the ESR signal intensity and to identify the stability of radicals under 77 days of storage. Raw chicken eggs were irradiated with doses of 0, 0.5, 1, 2, 3 and 5 kGy at room temperature using a Co-60 irradiator. The samples were prepared by separating, drying and powdering shells from the raw eggs. The irradiated chicken egg shells presented an asymmetric absorption in shape at g$_1$=2.0023$\pm$0.00004 and g$_2$=1.9979$\pm$0.00005, different from the non-irradiated ones. The strength of the ESR signal increased linearly with the applied doses (to S kGy). The intensity of the ESR signals after irradiation were stable even after 77-day of storage at 5$^{\circ}C$ and/or room temperature.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.996-1001
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• 2006

Automatic washing machines have been improved and popularized steadily since the first electric washing machine was produced in the early 1900's. Appliance industry has tried to obtain the performance of washing machine with large capacity, high energy efficiency, low vibration and low noise levels. As the installation peace of a washer becomes closer to the living space, vibration and noise problems become more important challenges. In general, a washing machine has four legs to support its body. Four legs of the washing machine should be attached on a floor. If not so, it may cause severe vibration or walking in the spin-drying process. Unfortunately, the floor of an ordinary house is bumpy in general, and the consumers will not accept bolting washing machines to a foundation; moreover, sometimes they move the location of their washing machines to utility rooms or bath rooms or kitchens and don't care for leveling the legs exactly. In this study, we devise an auto-leg system that prevents the occurrence of abnormal vibration and walking of washing machines. It is simply composed of a spring and a friction damper. Some experiments are implemented to show the dynamic characteristics of the three-dimensional auto-legged washing machine model that is located on the even or uneven ground. A spring parameter is optimized to adjust the length of the auto-leg system automatically up to 10 mm irregularity, and the friction damper is designed to decrease a resonance induced by the spring of the auto-leg system. Some numerical results show that placing the proposed auto-leg system in a washing machine makes good performance with low vibration, as well as low noise, regardless of the unevenness of the floor.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.254-254
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• 2011

The memories with nano-particles are very attractive because they are promising candidates for low operating voltage, long retention time and fast program/erase speed. In recent, various nano-floating gate memories with metal-oxide nanocrystals embedded in organic and inorganic layers have been reported. Because of the carrier generation in semiconductor, induced photon pulse enhanced the program/erase speed of memory device. We studied photo-induced electrical properties of these metal-oxide nanocrystal memory devices. At first, 2~10-nm-thick Sn and In metals were deposited by using thermal evaporation onto Si wafer including a channel with $n^+$ poly-Si source/drain in which the length and width are 10 ${\mu}m$ each. Then, a poly-amic-acid (PAA) was spin coated on the deposited Sn film. The PAA precursor used in this study was prepared by dissolving biphenyl-tetracarboxylic dianhydride-phenylene diamine (BPDA-PDA) commercial polyamic acid in N-methyl-2-pyrrolidon (NMP). Then the samples were cured at 400$^{\circ}C$ for 1 hour in N atmosphere after drying at 135$^{\circ}C$ for 30 min through rapid thermal annealing. The deposition of aluminum layer with thickness of 200 nm was followed by using a thermal evaporator, and then the gate electrode was defined by photolithography and etching. The electrical properties were measured at room temperature using an HP4156a precision semiconductor parameter analyzer and an Agilent 81101A pulse generator. Also, the optical pulse for the study on photo-induced electrical properties was applied by Xeon lamp light source and a monochromator system.