• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.2
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• pp.95-102
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• 2001

Nano-scale gate length MOSFET devices require extremely shallow source/drain eftension region with junction depth of 20∼30nm. In this work, 20nm $n^{+}$-p junctions that are realized by using this $As_{2}^{+}$ low energy ($\leq$10keV) implantation show the lower sheet resistance of the $1.0k\Omega$/$\square$ after rapid thermal annealing process. The $As_{2}^{+}$ implantation and RTA process make it possible to fabricate the nano-scale NMOSFET of gate length of 70nm. $As_{2}^{+}$ 5 keV NMOSFET shows a small threshold voltage roll-off of 60mV and a DIBL effect of 87.2mV at 100nm gate length devices. The electrical characteristics of the fabricated devices with the heavily doped and abrupt $n^{+}$-p junctions ($N_{D}$〉$10^{20}$$cm^{-3}$, $X_{j}$$\leq$20nm) suggest the feasibility of the nano-scale NMOSFET device fabrication using the $As_{2}^{+}$ low energy ion implantation.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.993-994
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• 2008

Electrochromic (EC) devices are capable of reversibly changing their optical properties upon charge injection and extraction induced by the external voltage. The characteristics of the EC device, such as low power consumption, high coloration efficiency, and memory effects under open circuit status, make them suitable for use in a variety of applications including smart windows and electronic papers. Coloration due to reduction or oxidation of redox chromophores can be used for EC devices (e-paper), but the switching time is slow (second level). Recently, with increasing demand for the low cost, lightweight flat panel display with paper-like readability (electronic paper), an EC display technology based on dye-modified $TiO_2$ nanoparticle electrode was developed. A well known organic dye molecule, viologen, was adsorbed on the surface of a mesoporous $TiO_2$ nanoparticle film to form the EC electrode. On the other hand, ZnO is a wide bandgap II-VI semiconductor which has been applied in many fields such as UV lasers, field effect transistors and transparent conductors. The bandgap of the bulk ZnO is about 3.37 eV, which is close to that of the $TiO_2$ (3.4 eV). As a traditional transparent conductor, ZnO has excellent electron transport properties, even in ZnO nanoparticle films. In the past few years, one-dimension (1D) nanostructures of ZnO have attracted extensive research interest. In particular, 1D ZnO nanowires renders much better electron transportation capability by providing a direct conduction path for electron transport and greatly reducing the number of grain boundaries. These unique advantages make ZnO nanowires a promising matrix electrode for EC dye molecule loading. ZnO nanowires grow vertically from the substrate and form a dense array (Fig. 1). The ZnO nanowires show regular hexagonal cross section and the average diameter of the ZnO nanowires is about 100 nm. The cross-section image of the ZnO nanowires array (Fig. 1) indicates that the length of the ZnO nanowires is about $6\;{\mu}m$. From one on/off cycle of the ZnO EC cell (Fig. 2). We can see that, the switching time of a ZnO nanowire electrode EC cell with an active area of $1\;{\times}\;1\;cm^2$ is 170 ms and 142 ms for coloration and bleaching, respectively. The coloration and bleaching time is faster compared to the $TiO_2$ mesoporous EC devices with both coloration and bleaching time of about 250 ms for a device with an active area of $2.5\;cm^2$. With further optimization, it is possible that the response time can reach ten(s) of millisecond, i.e. capable of displaying video. Fig. 3 shows a prototype with two different transmittance states. It can be seen that good contrast was obtained. The retention was at least a few hours for these prototypes. Being an oxide, ZnO is oxidation resistant, i.e. it is more durable for field emission cathode. ZnO nanotetropods were also applied to realize the first prototype triode field emission device, making use of scattered surface-conduction electrons for field emission (Fig. 4). The device has a high efficiency (field emitted electron to total electron ratio) of about 60%. With this high efficiency, we were able to fabricate some prototype displays (Fig. 5 showing some alphanumerical symbols). ZnO tetrapods have four legs, which guarantees that there is one leg always pointing upward, even using screen printing method to fabricate the cathode.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.4
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• pp.319-327
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• 2004

The Electronic compass made as a pilot model in this research is comprised of a three axis magnetic sensor, an accustar clinometer, and a fiber optic gyro sensor. The results confirming the output character, performance, and the accuracy of the deviation corrects of each sensor are as follows: 1) As for the output character of the three axis magnetic sensor, the magnetic field showed a cosine curve on the X axis, a - sine curve on the Y axis, and constant figures on the Z sensor. The horizontal component H and the vertical component V of the terrestrial magnetism calculated from the output voltage were 33.2${\mu}$T and 23.95${\mu}$T respectively. 2) When the fiber optic gyro sensor is fixed on the electromotive rotation transformation and has made a clockwise rotation with the speed of 10/sec, 20/sec, and 30/sec, the relationship between the output and the rotation angle of the fiber optic gyro sensor showed proportionally constant values. 3) When the magnetic field was induced with a magnet, the deviation before the correction was significant at a high of 25. However, the deviation after the correction using Poisson correction was in the 2 range, significantly lower than before the correction. It was confirmed that automatic deviation corrects are possible with the electronic compass made as a pilot model in this research.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.5
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• pp.19-25
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• 2008

In this study, we fabricated Organic Thin Film Transistors(OTFTs) with $C_{60}$ hole injection layer between organic semiconductor(pentacene) and metal electrode, and we compared the electrical characteristics of OTFTs with/without $C_{60}$. When the $C_{60}$ hole injection layer was introduced, the mobility and the threshold voltage were improved from 0.298 $cm^2/V{\cdot}s$ and -13.3V to 0.452 $cm^2/V{\cdot}s$ and -10.8V, and the contact resistance was also reduced. When the $C_{60}$ is inserted, the hole injection was enhanced because the $C_{60}$ prevent the unwanted chemical reaction between pentacene and Au. Furthermore, we fabricated the OTFTs using Al as their electrodes. When the OTFTs were made by only aluminum electrode, the channel were not mostly made because of the high hole injection barrier between pentacene and aluminum, but when the $C_{60}$ layer with an optimal thickness was applied between aluminum and pentacene, the device performances were obviously enhanced because of the vacuum energy level shift of Al and the consequent decrease of the hole injection barrier which was induced by the interface dipole formation between $C_{60}$ and Al. The mobility and $I_{ON}/I_{OFF}$ current ratio of OTFT with $C_{60}/Al$ electrode were 0.165 $cm^2/V{\cdot}s$ and $1.4{\times}10^4$ which were comparable with the normal Au electrode OTFT.

• Journal of the Korean Society of Safety
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• v.15 no.2
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• pp.70-77
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• 2000

For hazardous air pollutants(HAP) such as NO, $NO_2$ and $SO_2$ decomposition efficiency, power consumption, and applied voltage were investigated by SPCP(Surface induced discharge Plasma Chemical Processing) reactor to obtain optimum process variables and maximum decomposition efficiencies. Decomposition efficiency of HAP with various electric frequencies(5~50 kHz), flow rates(100~1,000 mL/min), initial concentrations(100~1,000 ppm) and additive($CH_4$) were measured and the products were analyzed with FT-IR. Experimental results showed that for the frequency of 10 kHz, the highest decomposition efficiency of 94.3 % for NO, 84.7 % for $NO_2$ and 99 % far $SO_2$ were observed at the power consumptions of 19.8, 20 and 19W, respectively, and that decomposition efficiency decreased with increasing frequency above 20 kHz. And decomposition efficiency per unit power were 5.21 %/W for $SO_2$, 4.76 %/W for NO and 4.24 %/W for $NO_2$ and the highest decomposition efficiency was observed with $SO_2$. Decomposition efficiency was increased with increasing residence times and with decreasing initial concentration of pollutants. When the additive of $CH_4$ was used, decomposition efficiency was increased with increasing $CH_4$ content, and NO, $NO_2$ and $SO_2$ were almost completely decomposed with the efficiency of 99 %, 98 % and 99 %, respectively and therefore $CH_4$ was a good additive material. The optimum power for the maximum decomposition efficiency were 7.5 W for $SO_2$, 9.5 W for NO and 15.5 W for $NO_2$, respectively. Optimum power with the maximum decomposition efficiency were 9.5 W at 1,000 ppm of NO, 7~8 W at 100~500 ppm of NO and 15.5 W at all concentration range of $NO_2$ and 11.5 W at 1,000 ppm, 4.9 W at 500 ppm, 3.7 W at 100~300 ppm of $SO_2$ and power efficiency was best in these case.

• The Korean Journal of Physiology and Pharmacology
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• v.22 no.5
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• pp.539-546
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• 2018

Botulinum toxin type A (BoNT/A) has been used therapeutically for various conditions including dystonia, cerebral palsy, wrinkle, hyperhidrosis and pain control. The substantia gelatinosa (SG) neurons of the trigeminal subnucleus caudalis (Vc) receive orofacial nociceptive information from primary afferents and transmit the information to higher brain center. Although many studies have shown the analgesic effects of BoNT/A, the effects of BoNT/A at the central nervous system and the action mechanism are not well understood. Therefore, the effects of BoNT/A on the spontaneous postsynaptic currents (sPSCs) in the SG neurons were investigated. In whole cell voltage clamp mode, the frequency of sPSCs was increased in 18 (37.5%) neurons, decreased in 5 (10.4%) neurons and not affected in 25 (52.1%) of 48 neurons tested by BoNT/A (3 nM). Similar proportions of frequency variation of sPSCs were observed in 1 and 10 nM BoNT/A and no significant differences were observed in the relative mean frequencies of sPSCs among 1-10 nM BoNT/A. BoNT/A-induced frequency increase of sPSCs was not affected by pretreated tetrodotoxin ($0.5{\mu}M$). In addition, the frequency of sIPSCs in the presence of CNQX ($10{\mu}M$) and AP5 ($20{\mu}M$) was increased in 10 (53%) neurons, decreased in 1 (5%) neuron and not affected in 8 (42%) of 19 neurons tested by BoNT/A (3 nM). These results demonstrate that BoNT/A increases the frequency of sIPSCs on SG neurons of the Vc at least partly and can provide an evidence for rapid action of BoNT/A at the central nervous system.

• Biomolecules & Therapeutics
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• v.26 no.5
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• pp.439-445
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• 2018

T-type calcium channels are low voltage-activated calcium channels that evoke small and transient calcium currents. Recently, T-type calcium channels have been implicated in neurodevelopmental disorders such as autism spectrum disorder and neural tube defects. However, their function during embryonic development is largely unknown. Here, we investigated the function and expression of T-type calcium channels in embryonic neural progenitor cells (NPCs). First, we compared the expression of T-type calcium channel subtypes (CaV3.1, 3.2, and 3.3) in NPCs and differentiated neural cells (neurons and astrocytes). We detected all subtypes in neurons but not in astrocytes. In NPCs, CaV3.1 was the dominant subtype, whereas CaV3.2 was weakly expressed, and CaV3.3 was not detected. Next, we determined CaV3.1 expression levels in the cortex during early brain development. Expression levels of CaV3.1 in the embryonic period were transiently decreased during the perinatal period and increased at postnatal day 11. We then pharmacologically blocked T-type calcium channels to determine the effects in neuronal cells. The blockade of T-type calcium channels reduced cell viability, and induced apoptotic cell death in NPCs but not in differentiated astrocytes. Furthermore, blocking T-type calcium channels rapidly reduced AKT-phosphorylation (Ser473) and $GSK3{\beta}$-phosphorylation (Ser9). Our results suggest that T-type calcium channels play essential roles in maintaining NPC viability, and T-type calcium channel blockers are toxic to embryonic neural cells, and may potentially be responsible for neurodevelopmental disorders.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.71-71
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• 2011

Dye-sensitized solar cells (DSCs) have drawn great academic attention due to their potential as low-cost renewable energy sources. DSCs contain a nanostructured TiO2 photoanode, which is a key-component for high conversion efficiency. Particularly, one-dimensional (1-D) nanostructured photoanodes can enhance the electron transport for the efficient collection to the conducting substrate in competition with the recombination processes. This is because photoelectron colletion is determined by trapping/detrapping events along the site of the electron traps (defects, surface states, grain boundaries, and self-trapping). Therefore, 1-D nanostructured photoanodes are advantageous for the fast electron transport due to their desirable features of greatly reduced intercrystalline contacts with specified directionality. In particular, anodic TiO2 nanotube (NT) electrodes recently have been intensively explored owing to their ideal structure for application in DSCs. Besides the enhanced electron transport properties resulted from the 1-D structure, highly ordered and vertically oriented nanostructure of anodic TiO2 NT can contribute additional merits, such as enhanced electrolyte diffusion, better interfacial contact with viscous electrolytes. First, to confirm the advantages of 1-D nanostructured material for the photoelectron collection, we compared the electron transport and charge recombination characteristics between nanoparticle (NP)- and nanorod (NR)-based photoanodes in DSCs by the stepped light-induced transient measurements of photocurrent and voltage (SLIM-PCV). We confirmed that the electron lifetime of the NR-based photoanode was much longer than that of the NP-based photoanode. In addition, highly ordered and vertically oriented TiO2 NT photoanodes were prepared by electrochemical anodization method. We compared the photovoltaic properties of DSCs utilizing TiO2 NT photoanodes prepared by one-step anodization and two-step anodization. And, to reduce the charge recombination rate, energy barrier layer (ZnO, Al2O3)-coated TiO2 NTs also applied in DSC. Furthermore, we applied the TiO2 NT photoanode in DSCs using a viscous electrolyte, i.e., cobalt bipyridyl redox electrolyte, and confirmed that the pore structure of NT array can enhance the performances of this viscous electrolyte.

• Korean Journal of Food Science and Technology
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• v.31 no.2
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• pp.410-415
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• 1999

Yakju was sterilized with high-voltage pulses of short time of a continuous pulsed electric field (PEF) system. The initial microbial counts of Yakju were $2.2{\times}10^{5}$ CFU/mL for total aerobes. The pH, acidity and electric conductivity of Yakju were 3.82, 0.37% and 1.24 mS/cm, respectively. Yakju was treated with exponential-wave formed electric pulses of 100 Hz for $0{\sim}4000{\mu}s$ under the field strength of $20{\sim}35\;kV/cm$. The lethal effect of electric fields on microorganisms was resulted from the breakdown of the cell membrane induced by the transmembrane electric potential. The critical values of the external field for the sterilization were 16.0 kV/cm for total aerobes. Logarithmic survival rates decreased linearly at low electric field strength, but curvilinearly at high electric field strength with treatment time. The sterilization of Yakju was more largely affected by the electric field strength than by the treatment time. Any changes in pH, acidity, and the growth of microorganisms were not found in the PEF treated Yakju during the storage at both $4^{\circ}C\;and\;30^{\circ}C$.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.489-492
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• 2005

We report new polymer stabilized ferroelectric liquid crystal (PSFLC) cells with mechanical stability which is achievable by introducing photospacers in the cells. It was found that the mechanical st ability of the PSFLC cell was effected by introduction of photo spacers. We analyzed the dependence of mechanical stability and memory property on the density of photospacers in the PSFLC cell. The stability and memory properties of PSFLC Cells depending on photospacer density are discussed. 1. Introduction Recently, flexible displays have attracted much attention because they have remarkable advantages: thinner, lighter, non-breakable and conformable features. Flexible displays have various potential applications such as e-book and e-paper displays utilizing the distinct features. E-book and E-paper displays demand very low power consumption, so that bistable memory liquid crystal modes are required in case of flexible plastic LCDs for those application. Three kinds of memory LC modes have been developed; bistable nematic, bistable cholesteric and bistable FLC. Among them SSFLC as one of bistable FLC has big advantages such as low driving voltage, wide view angle and fast response time, SSFLC cells are, however, very weak against mechanical shock. Polymer stabilized FLC (PSFLC) has been developed to overcome the poor mechanical stability of SSFLC. PSFLC was known to have network structure that FLCs are oriented with smectic layer ordering in polymer network. The polymer network stabilizes the FLC orientation, which leads to improvement of mechanical stability of PSFLCD. A lot of studies have been done for the application of PSFLC to flexible $LCDs.^{[1{\sim}12]}$ However, it should be noted that PSFLC does not have sufficient mechanical stability for the particular applications such as smart card LCD, where LCD is highly bendable.Bead spacer was mainly used to maintain cell gap of conventional PSFLCDs. But the spacer density of it is not locally uniform in the cell, so that it is generally difficult that the PSFLCDs with bead spacers show sufficient mechanical stability. In order to more improve the mechanical stability of PSFLCDs, we introduced photospacers into PSFLCDs. In this paper, we describe the improvement of mechanical stability by introducing photospacers into PSFLCDs.