• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.41-43
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• 1999

Among the feffoelectric thin films that have been widely investigated for ferroelectric random access memory (FRAM) applications, SrBi$_2$Ta$_2$$O_{9}$ thin film is appropriate to memory capacitor materials for its excellent fatigue endurance. However, very few studies on etch properties of SBT thin film have been reported although dry etching is an area that demands a great deal of attention in the very large scale integrations. In this study, the a SrBi$_2$Ta$_2$$O_{9}$ thin films were etched by using magnetically enhanced inductively coupled Ar/CHF$_3$ plasma. Etch properties, such as etch rate, selectivity, and etched profile, were measured according to gas mixing ratio of CHF$_3$(Ar$_{7}$+CHF$_3$) and the other process conditions were fixed at RF power of 600 W, dc bias voltage of 150 V, chamber pressure of 10 mTorr. Maximum etch rate of SBT thin films was 1750 A77in, under CHF$_3$(Ar+CHF$_3$) of 0.1. The selectivities of SBT to Pt and PR were 1.35 and 0.94 respectively. The chemical reaction of etched surface were investigated by X-ray photoelectron spectroscopy (XPS) analysis. The Sr and Ta atoms of SBT film react with fluorine and then Sr-F and Ta-F were removed by the physical sputtering of Ar ion. The surface of etched SBT film with CHF$_3$(Ar+CHF$_3$) of 0.1 was analyzed by secondary ion mass spectrometer (SIMS). Scanning electron microscopy (SEM) was used for examination of etched profile of SBT film under CHF$_3$(Ar+CHF$_3$) of 0.1 was about 85˚.85˚.˚.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.10 s.89
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• pp.1011-1017
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• 2004

Ultra Wideband(UWB) technologies have been developed to exploit a new spectrum resource in substances and to realize ultra-high-speed communication, high precision geolocation, and other applications. The energy of UWB signal is extremely spread from near DC to a few GHz. This means that the interference between conventional narrowband systems and UWB systems is inevitable. However, the interference effects had not previously been studied from UWB wireless systems to conventional mobile wireless systems sharing the frequency bands such as Korean Cellular CDMA and WCDMA. This paper experimentally evaluates the interference from two kinds of UWB sources, namely a direct-sequence spread-spectrum CDMA(DS-CDMA) UWB source and an impulse radio UWB source, to a Cellular CDMA and WCDMA digital transmission system. The average frame error rate degradation of each system are presented. From these experimental results, the interference effects of DS-CDMA UWB source is not severe compared to the Impulse UWB.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.5
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• pp.378-384
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• 2003

Etching species in CF$_4$/Ar plasma and the behavior of etching rate of Bi$_4$-$_{x}$L$_{x}$rTi$_3$O$_2$ (BLT) films were investigated in inductively coupled plasma (ICP) reactor in terms of etch parameters. The etching rate as functions of CF$_4$ contents showed the maximum 803 $\AA$/min at 20% CF$_4$ addition in CF$_4$/Ar plasma. The increase of RF power and DC bias voltage caused to an increase of etch rate. The variation of relative volume densities for F and he atoms were measured with the optical emission spectroscopy (OES). The chemical states of BLT were investigated with using X-ray photoelectron spectroscopy (XPS). XPS narrow scan analysis shows that La-fluorides remained on the etched surface. The presence of maximum etch rate at CF$_4$(20%)/Ar(80%) may be explained by the concurrence of two etching mechanisms such as physical sputtering and chemical reaction. The roles of he ion bombardment include destruction of metal (Bi, La, Ti)-O bonds as well as assistant for chemical reaction of metals with fluorine atoms.oms.

• Journal of Sensor Science and Technology
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• v.5 no.6
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• pp.25-34
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• 1996

In this paper, we have designed signal conditioning circuitry for piezoresistive pressure sensor. Signal conditioning circuitry consists of voltage reference circuit for sensor driving voltage and instrument amplifier for sensor signal amplification. Signal conditioning circuitry is simulated using HSPICE in a single poly double metal $1.5\;{\mu}m$ BiCMOS technology. Simulation results of band-gap reference circuit showed that temperature coefficient of $21\;ppm/^{\circ}C$ at the temperature range of $0\;{\sim}\;70^{\circ}C$ and PSRR of 80 dB. Simulation results of BiCMOS amplifier showed that dc voltage gain, offset voltage, CMRR, CMR and PSRR are outperformed to CMOS and Bipolar, but power dissipation and noise voltage were more improved in CMOS than BiCMOS and Bipolar. Designed signal conditioning circuitry showed high input impedance, low offset and good CMRR, therefore, it is possible to apply sensor and instrument signal conditioning circuitry.

• Current Photovoltaic Research
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• v.3 no.4
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• pp.135-139
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• 2015

$Cu_2SnS_3$ (CTS) based thin film solar cells (TFSCs) are of great interest because of its earth abundant, low-toxic and eco-friendly material with high optical absorption coefficient of $10^4cm^{-1}$. In this study, the DC sputtered precursor thin films have been sulfurized using rapid thermal annealing (RTA) system in the graphite box under Ar gas atmosphere for 10 minute. The systematic variation of sulfur powder during annealing process has been carried out and their effects on the structural, morphological and optical properties of CTS thin films have been investigated. The preliminary power conversion efficiency of 1.47% with a short circuit current density of $33.9mA/cm^2$, an open circuit voltage of 159.7 mV, and a fill factor of 27% were obtained for CTS thin film annealed with 0.05g of S powder, although the processing parameter s have not yet been optimized.

• Journal of Energy Engineering
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• v.16 no.4
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• pp.181-186
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• 2007

In order to investigate the heat transfer coefficient and pressure drop during evaporation of $CO_2$, basic experiment on the evaporation heat transfer characteristics in a horizontal smooth tube was performed. The experimental apparatus consisted of a test section, a DC power supply, a heater, a chiller, a mass flow meter, a pump and a measurement system. Experiment was conducted for various mass fluxes ($200{\sim}1200\;kg/m^2s$), heat fluxes ($10{\sim}80\;kW/m^2$) and saturation temperatures ($-5{\sim}5^{\circ}C$). With the increase of quality, the evaporation heat transfer coefficient decreased. With the increase of heat flux, the evaporation heat transfer coefficient increased. Significantly change of the heat transfer coefficient was observed at any heat flux and mass flux. With the increase of saturation temperature, the heat transfer coefficient increased. Pressure drop increased with the increase of mass flux and the decrease of saturation temperature.

• Journal of the Korean Society of Safety
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• v.24 no.4
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• pp.28-33
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• 2009

This study examined the mounting status of cigar lighter receptacles for vehicles and analyzed the tracking phenomenon that occurs when foreign material entered a cigar lighter receptacle to obtain data for the analysis of accident investigation. Regardless of the vehicle's output, cigar lighter receptacles are mounted in a vehicle horizontally, vertically, or at tilting or inclined angle. The tilting type cigar lighter receptacle is much easier to use but current leakage resulting from foreign materials (coffee, beverages, water, etc.) falling into the cigar lighter receptacle may cause a fire to start. This study used a vehicle battery (DC 12V) as a power supply for the tracking test and configured its circuit in the same way as that of an electrical device in a vehicle. The tracking phenomenon that occurred in the standby mode of the vehicle exhibited a fine flame and an irregular occurrence of smoke. While this tracking phenomenon was occurring, the leakage current and the reaching distance of the flame were measured to be approximately 930mA and $20{\sim}50cm$, respectively. It is thought that the resultant flame may ignite toluene, dust, cigarettes, etc. It was observed that as the tracking progressed, the internal metal socket melted and a hole was created, the surface of which was also severely carbonized. In addition, the electrical resistance of the carbonized conductive path was measured to be approximately $30{\Omega}$. It is thought that this much resistance may cause local heating when leakage current flows and could ignite any nearby flammable material.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.380-381
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• 2007

This paper reports on the deposition conditions and properties of ITO films used as electrode layer in a organic light emitting diodes on a PET substrate. The deposition technique employed was specially designed roll-to-roll sputtering. The oxide was deposited at room temperature in an argon and oxygen plasma on a transparent conducting ITO layer on a PET film. The influence of deposition parameters such as DC power, working pressure and oxygen partial pressure has been investigated, in order to obtain the best compromise between a high deposition rate and adequate electro-optical properties. Electrical and optical properties of ITO films were analyzed by Hall measurement examinations with van der pauw geometry at room temperature and UV/Vis spectrometer analysis, respectively. In addition, the structural properties and surface smoothness were measured by x-ray diffraction and scaning electron microscopy, respectively. From optimized ITO films grown by roll-to-roll sputter system, good electrical$(6.44{\times}10^{-4}\;{\Omega}-cm)$ and optical(above 86 % at 550 nm) properties were obtained. Also, the ITO films exhibited amorphous structure and very flat surface beacause of low deposition temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.7
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• pp.503-509
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• 2013

In this study, $Cu(In_{1-x},Ga_x)Se_2$ (CIGS) thin films were prepared on the Mo coated soda-lime glass by the DC magnetron sputtering and a subsequent selenization process. For the selenization process, selenization rapid thermal process(RTP) with cracker cell, which was helpful to smaller an atomic of Se, was adopted. To make CIGS layer, they were then annealed with the cracked Se. Based on this selenization method, we made several CIGS thin film and investigated the effects of In deposition time, and selenization time. Through x-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and atomic force microscopy (AFM), it is found that the Mo/In/CuGa structure and the high sputtering power shows the dominant chalcopyrite structure and have a uniform distribution of the grain size. The CIGS films with the In deposition time of 5 min has the best structure due to the smooth surface. And CIGS films with the selenization time of 50 min show good crystalline growth without any voids.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.11
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• pp.1241-1245
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• 2004

Continuous physical vapor deposition (PVD) method is one of many processes to fabricate long length coated conductor which is required for successful large-scale application of superconducting power devices. Three film deposition systems (pulsed laser deposition, sputtering, and evaporation) equipped with reel-to-reel(R2R) metal tape moving apparatus were installed and used to deposit multi-layer oxide thin films. Both RABiTS and IBAD texture templates are used. IBAD template consists of CeO$_2$(PLD)/YSZ(IBAD) on stainless steel(SS) metal tape, and RABiTS template has the structure of CeO$_2$/YSZ/Y$_2$O$_3$ which was continuously deposited on Ni-alloy tape using R$_2$R evaporation and DC reactive sputtering in a deposition system designed to do both processes. 0.4 m-long coated conductor with Ic(77 K) of 34 A/cm was fabricated using RABiTS template. 0.5 m and 1.1 m-long coated conductor with Ic(77 K) of 41 A/cm and 26 A/cm were fabricated using IBAD template.