• Journal of the Korean Vacuum Society
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• v.18 no.2
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• pp.79-84
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• 2009

The electron emission source of triode type has been fabricated using CNT paste. The nano Ag particle and photosensitive polymers were added to the CNT paste. The surface roughness of the CNT emitter was uniform by the back exposure method. The added nano Ag particle improves the adhesion and the electric conductance with small variation in the CNTs and between electrode. After the aging with heat-exhausting, the reliability of the triode CNT electron source was secured in the high voltage and current operation for 12 hours. At this time, the gate leakage current was about 10 % less than.

• Smart Structures and Systems
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• v.12 no.1
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• pp.55-71
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• 2013

Structural health monitoring (SHM) is vital for detecting the onset of damage and for preventing catastrophic failure of civil infrastructure systems. In particular, piezoelectric transducers have the ability to excite and actively interrogate structures (e.g., using surface waves) while measuring their response for sensing and damage detection. In fact, piezoelectric transducers such as lead zirconate titanate (PZT) and poly(vinylidene fluoride) (PVDF) have been used for various laboratory/field tests and possess significant advantages as compared to visual inspection and vibration-based methods, to name a few. However, PZTs are inherently brittle, and PVDF films do not possess high piezoelectricity, thereby limiting each of these devices to certain specific applications. The objective of this study is to design, characterize, and validate piezoelectric nanocomposites consisting of zinc oxide (ZnO) nanoparticles assembled in a PVDF copolymer matrix for sensing and SHM applications. These films provide greater mechanical flexibility as compared to PZTs, yet possess enhanced piezoelectricity as compared to pristine PVDF copolymers. This study started with spin coating dispersed ZnO- and PVDF-TrFE-based solutions to fabricate the piezoelectric nanocomposites. The concentration of ZnO nanoparticles was varied from 0 to 20 wt.% (in 5 % increments) to determine their influence on bulk film piezoelectricity. Second, their electric polarization responses were obtained for quantifying thin film remnant polarization, which is directly correlated to piezoelectricity. Based on these results, the films were poled (at 50 $MV-m^{-1}$) to permanently align their electrical domains and to enhance their bulk film piezoelectricity. Then, a series of hammer impact tests were conducted, and the voltage generated by poled ZnO-based thin films was compared to commercially poled PVDF copolymer thin films. The hammer impact tests showed comparable results between the prototype and commercial samples, and increasing ZnO content provided enhanced piezoelectric performance. Lastly, the films were further validated for sensing using different energy levels of hammer impact, different distances between the impact locations and the film electrodes, and cantilever free vibration testing for dynamic strain sensing.

• Journal of the Korean Institute of Telematics and Electronics
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• v.18 no.4
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• pp.49-61
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• 1981

A generally applicable computer simulation program for diffused silicon solar cells has been developed on the basis of the experimental results. The program can be easily used to obtain the spectral response and I-V characteristics for N+P, P+N N+PP+, P+NN+cells by changing various input parameters. The insolated spectra can be taken from AMI and constant intensity and GE - ELH lamp light sources. The options for AR coating are Si3N4 film and materials with constant reflectance including zero reflectance for ideal case. The computer simulation demonstrates successful results compared with the measured values for the short circuit current, open circuit voltage, efficiency, spectral response, quantum efficiency, I-V characteristics, etc. This program was used to optimize doping concentration, cell thickness, light concentration, junction depth, and to obtain the limit values for front surface recornbination velocity, effective carrier life time in the depletion regions and shunt resistance, and also to drive the changing rate in conversion efficiency depending on operation temperature, series resistance and electric field strength in N+P+ bulk regions.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.2
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• pp.49-52
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• 2006

Periodic electric field assisted poling low loss (${\sim}0.1dB/cm$) single-mode Ti-diffused waveguides in $LiNbO_3$ has been achieved using a periodically patterned electrode on the +Z surface of Ti : $LiNbO_3$ crystal and homogeneous LiCl solution. Using selective chemical etching, we confirmed the periodic (${\sim}16{\mu}m$) domain inverted structure and measured SH (second harmonic) properties of fabricated periodically poled Ti : $LiNbO_3$ waveguides.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.4
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• pp.24-31
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• 2005

A plused laser ablation deposition(PLAD) technique has been used for producing fine particle as well as thin film at relatively low substrate temperatures. However, in order to manufacture and evaluate such materials in detail, motions of plume particles generated by laser ablation have to be understood and interactions between the particles by ablation and gas plasma have to be clarified. Therefore this paper was focused on the understanding of plume motion in laser ablation assisted by hi plasmas at 100[mTorr]. One-dimensional hybrid model consisting of fluid and particle models was developed and three kinds of plume particles which are carbon atom(C), $ion(C^+)$ and electron were considered in the calculation of particle method. It was obtained that ablated $C^+$ was electrically captured in Ar plasmas by strong electric field(E). The difference between motions of the ablated electrons and $C^+$ made E strong and the collisional processes active. The energies of plume particles were investigated on a substrate surface. In addition the plume motion in Ar gas was also calculated and discussed.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06a
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• pp.5-18
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• 1996

The solid state cesium ion source os alumino-silicate based zeolite which contains cerium. The material is an ionic conductor. Cesiums are stably stored in the material and one can extract the cesiums by applying electric field across the electrolyte. Cesium ion bombardment has the unique property of producing high negative ion yield. This ion source is used as the primary source for the production of a negative ion without any gas discharge or the need for a carrier gas. The deposition of materials as an ionic species in the energy range of 1.0 to 300eV is recently recognized as a very promising new thin film technique. This energetic non-thermal equilibrium deposition process produces films by “Kinetic Bonding / Energetic Condensation" mechansim not governed by the common place thermo-mechanical reaction. Under these highly non-equilibrium conditions meta-stable materials are realized and the negative ion is considered to be an optimum paeticle or tool for the purpose. This process differs fundamentally from the conventional ion beam assisted deposition (IBAD) technique such that the ion beam energy transfer to the deposition process is directly coupled the process. Since cesium ion beam sputter deposition process is forming materials with high kinetic energy of metal ion beams, the process provider following unique advantages:(1) to synthesize non thermal-equilibrium materials, (2) to form materials at lower processing temperature than used for conventional chemical of physical vapor deposition, (3) to deposit very uniform, dense, and good adhesive films (4) to make higher doposition rate, (5) to control the ion flux and ion energy independently. Solid state cesium ion beam sputter deposition system has been developed. This source is capable of producing variety of metal ion beams such as C, Si, W, Ta, Mo, Al, Au, Ag, Cr etc. Using this deposition system, several researches have been performed. (1) To produce superior quality amorphous diamond films (2) to produce carbon nitirde hard coatings(Carbon nitride is a new material whose hardness is comparable to the diamond and also has a very high thermal stability.) (3) to produce cesiated amorphous diamond thin film coated Si surface exhibiting negative electron affinity characteristics. In this presentation, the principles of solid state cesium ion beam sputter deposition and several applications of negative metal ion source will be introduced.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.12
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• pp.80-90
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• 1994

To develop VLSI of higher packing density with 0.5.mu.m gate length of less, semiconductor devices require shallow junction with higher doping concentration. the most common method to form the shallow junction is ion implantation, but in order to remove the implantation induced defect and activate the implanted impurities electrically, ion-implanted Si should be annealed at high temperature. In this annealing, impurities are diffused out and redistributed, creating deep PN junction. These make it more difficult to form the shallow junction. Accordingly, to miimize impurity redistribution, the thermal-budget should be kept minimum, that is. RTA needs to be used. This paper reports results of the diffusion characteristics of PSG film by varying Phosphorus weitht %/ Times and temperatures of RTA. From the SIMS.ASR.4-point probe analysis, it was found that low sheet resistance below 100 .OMEGA./ㅁand shallow junction depths below 0.2.mu.m can be obtained and the surface concentrations are measured by SIMS analysis was shown to range from 2.5*10$^{17}$ aroms/cm$^{3}$~3*10$^{20}$ aroms/cm$^{3}$. By depending on the RTA process of PSG film on Si, LDD-structured nMOSFET was fabricated. The junction depths andthe concentration of n-region were about 0.06.mu.m. 2.5*10$^{17}$ atom/cm$^{-3}$ , 4*10$^{17}$ atoms/cm$^{-3}$ and 8*10$^{17}$ atoms/cm$^{3}$, respectively. As for the electrical characteristics of nMOS with phosphorus junction for n- region formed by RTA, it was found that the characteristics of device were improved. It was shown that the results were mainly due to the reduction of electric field which decreases hot carriers.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.8
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• pp.790-796
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• 2011

The system which is exposed in the impact range of High-altitude Electromagnetic Pulse(HEMP) may get serious damage because HEMP has a very large electric field value, a very fast rise-time, and so on. Electromagnetic analysis should be performed for signals coupled to the opening or cables of the system prior to derive the system design specifications in order to protect the system against HEMP adequately. In this paper, we analyzed the HEMP coupled signals for the coaxial cable which is generally used to transmit and receive video or RF signals and compared the coupled signal of the one wire with that of the inner conductor of a coaxial cable to confirm the decreased effect of HEMP by the shield. The coaxial cable is analyzed by the external and internal region of the shield separately. For the external region of the coaxial cable, general scattered equation was applied to calculate currents on the surface of the shield and for internal region of the coaxial cable, chain matrix algorithm is used. To verify this paper the analyzed results were compared the results of the existing paper and the two results have good agreements.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.8
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• pp.1068-1076
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• 1997

Emission control of acid exhaust gases from coal-fired power plants and waste incinerators has become an increasing concern of both industries and regulators. Among those gaseous emissions, SO$_{2}$ has been eliminated by a Spray Drying Absorber (SDA) system, where the exhaust gas is mixed with atomized limestone-water slurry droplets and then the chemical reaction of SO$_{2}$ with alkaline components of the liquid feed forms sulfates. Liquid atomization is necessary because it maximizes the reaction efficiency by increasing the total surface area of the alkaline components. An experimental study was performed with a laboratory scale SDA to investigate whether the scrubbing efficiency for SO$_{2}$ reduction increased or not with the application of a DC electric field to the limestone-water slurry. For a selected experimental condition SO$_{2}$ concentrations exited from the reactor were measured with various applied voltages and liquid flow rates. The applied voltage varied from -10 to 10 kV by 1 kV, and the volume flow rate of slurry was set to 15, 25, 35 ml/min which were within the range of emission mode. Consequently, the SO$_{2}$ scrubbing efficiency increased with increasing the applied voltage but was independent of the polarity of the applied voltage. For the electrical and flow conditions considered a theoretical study of estimating average size and charge of the atomized droplets was carried out based on the measured current-voltage characteristics. The droplet charge to mass ratio increased and the droplet diameter decreased as the strength of the applied voltage increased.

• Journal of the Korean Magnetics Society
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• v.6 no.2
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• pp.106-111
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• 1996

Electric machines such as motors which have rmving parts are designed for producing mechanical force or torque. The accurate calculations of electromagnetic force and torque are important in the design these machines. Electromagnetic force calculation method using the results of Finite Element Method(FEM) has been presented variously in 2-D problems. Typically the Maxwell's Stress Tensor method and the method of virtual work are used. The former calculates forces by integrating the surface force densities which can be expressed in terms of Maxwell Stress Tensor(MST), and the latter by differentiating the electromagnetic energy with respect to the virtual dis¬placement of rigid bodies of interest. In the problems including current source, magnetic vector potentials(MVP) have rmstly been used as unknown variables for field analysis by a numerical method; e. g. FEM. This paper, thus, introduces the two both methods using MVP in 3-D case. To verify the usefulness of presented methods, a solenoid model is chosen and analyzed by 3-D and axisymmetric FEM. It is found that the force calculation results are in good agreement for several mesh schemes.