• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.279-279
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• 2007

Synthesis and dielectric properties of glass-ceramic composites with zinc borosilicate glass(here after ZBS glass) were investigated as functions of $ZnAl_2O_4$ phase synthesis method, glass addition (50~60 vol%) and sintering temperature ($600{\sim}950^{\circ}C$ for 2 hrs). The 50 vol% ZBS glass-$Al_2O_3$ and 60 vol% ZBS glass-$ZnAl_2O_4$ ensured successful sintering below $900^{\circ}C$. But the composition of 100-x-y vol% ZBS glass-x vol% $Al_2O_3-y$ vol% ZnO exhibited poor sinterability below $900^{\circ}C$ and the swelling phenomenon occurred in this composite with the large amount of ZBS glass. The sintering behavior of Glass-ceramic composites was affected by the crystallization of $ZnAl_2O_4$ which was formed by the reaction between ZBS glass and $Al_2O_3$. Dielectric constant (${\varepsilon}_r$), $Q{\times}f$ value and temperature coefficient of resonant frequency (${\tau}_f$) of the composite with 50 and 60 vol% ZBS glass contents demonstrated $ZBS-Al_2O_3({\varepsilon}_r=5.7)$, $ZBS-ZnAl_2O_4({\varepsilon}_r=5.8)$ which is applicable to substrate requiring an low dielectric properties.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.74-77
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• 2004

[ $HfO_2$ ] dielectric layers were grown on the p-type Si(100) substrate by metalorganic molecular beam epitaxy(MOMBE). Hafnium $t-butoxide[Hf(O{\cdot}t-C_4H_9)_4]$ was used as a Hf precursor and Argon gas was used as a carrier gas. The thickness of the layers was measured by scanning electron microscopy (SEM) and high-resolution transmission electron measurement(HR-TEM). The properties of the $HfO_2$ layers were evaluated by X-ray diffraction(XRD), high frequency capacitance-voltage measurement(HF C-V), current-voltage measurement(I-V), and atomic force measurement(AFM). HF C-V measurements have shown that $HfO_2$ layer grown by MOMBE has a high dielectric constant(k=19-21). The properties of $HfO_2$ films are affected by various process variables such as substrate temperature, bubbler temperature, Ar, and $O_2$ gas flows. In this paper, we examined the relationship between the $O_2/Ar$ gas ratio and the electrical properties of $HfO_2$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.320-321
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• 2005

The $ZnNb_2O_6$ ceramics with 5wt% CuO and 5wt% $B_2O_3$ were prepared by the conventional mixed oxide method. The ceramics were sintered at the temperature of $950^{\circ}C\sim1025^{\circ}C$ for 3hr. in air. The structural properties were investigated with sintering temperature by XRD and SEM. Also, the microwave dielectric properties were investigated with sintering temperature. Increasing the sintering temperature, the peak of second phase ($Cu_3Nb_2O_8$) was increased. But no significant difference was observed as sintering temperature. In the $ZnNb_2O_6$ ceramics with 5wt% CuO and 5wt% $B_2O_3$ sintered at $975^{\circ}C$ for 3hr, the dielectric constant, quality factor and temperature coefficient of the resonant frequency were 19.30, 14,662GHz, +4.1$8ppm/^{\circ}C$, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.6
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• pp.470-475
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• 2009

We deposited $Al_2O_3$ thin films on GaN by remote plasma atomic layer deposition (RPALD) technique, trimethylaluminum(TMA) and oxygen were used as precursors, at fixed process condition, the number of cycle were changed. Growth rate per cycle was $1.2\;{\AA}$/cycle. and Growth rate was in proportion to a number of cycle, the GaN MIS capacitors that $Al_2O_3$ thin film were deposited above 12 nm, have excellent electrical properties, a low electrical leakage current density(${\sim}10^{-10}\;A/cm^2$ at 1.5 MV), but below 12 nm, we can see the degradation of the leakage current density. After post deposition annealing, Dielectric constant was estimated by 1 MHz high-frequency C-V method, it was varied with the anealing temperature from 6.9 at no post anealed to 7.6 at $800^{\circ}C$, and we can see a improvement of the leakage current density and breakdown voltage by post deposition anealing below $700^{\circ}C$, but, after anealed at $800^{\circ}C$, we can see the degradation of the leakage current density and breakdown voltage.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.533-533
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• 2007

The stress effect of SiGe p-type metal oxide semiconductors field effect transistors(MOSFETs) has been investigated to compare device properties using Si bulk and partially depleted silicon on insulator(PD SOI). The electrical properties in SiGe PD SOI presented enhancements in subthreshold slope and drain induced barrier lowering in comparison to SiGe bulk. The reliability of gate oxides on bulk Si and PD SOI has been evaluated using constant voltage stressing to investigate their breakdown (~ 8.5 V) characteristics. Gate leakage was monitored as a function of voltage stressing time to understand the breakdown phenomena for both structures. Stress induced leakage currents are obtained from I-V measurements at specified stress intervals. The 1/f noise was observed to follow the typical $1/f^{\gamma}$ (${\gamma}\;=\;1$) in SiGe bulk devices, but the abnormal behavior ${\gamma}\;=\;2$ in SiGe PD SOI. The difference of noise frequency exponent is mainly attributed to traps at silicon oxide interfaces. We will discuss stress induced instability in conjunction with the 1/f noise characteristics in detail.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.551-554
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• 2005

The method of the reduction of the automotive induction noise can be classified by the method of passive control and the method of active control. However, the passive control method has a demerit to reduce the effect of noise reduction at low frequency (below 500Hz) range and to be limited by a space of the engine room. Whereas, the active control method can overcome the demerit of passive control method. The algorithm of active control is mostly used the LMS (Least-Mean-Square) algorithm because the LMS algorithm can easily obtain the complex transfer function in real-time. Especially, When the Filtered-X LMS (FXLMS) algorithm is applied to an ANC system. However, the convergence performance of LMS algorithm goes bad when the FXLMS algorithm is applied to an active control of the induction noise under rapidly accelerated driving conditions. Thus Normalized FXLMS algorithm was developed to improve the control performance under the rapid acceleration. The advantage of Normalized FXLMS algorithm is that the step size is no longer constant. Instead, it varies with time. But there is one additional practical difficulty that can arise when a nonstationary input is used. If the input is zero for consecutive samples, then the step size becomes unbounded. So, in order to solve this problem. the Correlation FXLMS algorithm was developed. The Correlation FXLMS algorithm is realized by using an estimate of the cross correlation between the adaptation error and the filtered input signal to control the step size. In this paper, the performance of the Correlation FXLMS Is presented in comparison with that of the other FXLMS algorithms based on computer simulations.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.4
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• pp.291-298
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• 2007

This paper presents a signal processing algorithm to control the dynamic bandwidth of a single-degree-of-freedom (SDF) dynamic sensor system. An accelerometer is a representative SDF sensor system. In this paper, a moire-fringe-based fiber optic accelerometer is newly used for the test of the algorithm. The accelerometer is composed of one mass, one damper and one spring as a SDF dynamic system. In order to increase the dynamic bandwidth of the accelerometer, it is needed to increase the spring constant or decrease the mass. However, there are mechanical difficulties of this adjustment. Therefore, the presented signal processing algorithm is very effective to overcome the difficulties because it is just adjustment in the signal processing software. In this paper, the novel fiber optic accelerometer is introduced shortly, and the algorithm is applied to the fiber optic accelerometer to control its natural frequency and damping ratio. Several simulations and experiments are carried out to prove the performance of the algorithm. As a result, it is shown that the presented signal processing algorithm is a good way to broaden the dynamic bandwidth of the fiber optic accelerometer.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.4
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• pp.39-49
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• 2002

In this paper, the characteristics of RB(rubber bearing) were studied by various prototype tests on RB with low hardness rubber. The characteristics of RB were tested on displacements, repeated cycles, frequencies, vertical pressures, temperature, vertical stiffness and the capability of shear deformation. The prototype test showed that the displacement and vertical pressures were the most governing factors influencing on characteristics of RB. The effective stiffness and equivalent damping of RB showed small increment in high frequency range. After the repeated cyclic test with 50's cycles, the effective stiffness and equivalent damping of RB were almost constant compared with those of the 1st cycles due to low hysteretic damping. The shear modulus of RB was reduced after large deformation, and this value of RB was partly recovered after 40 days. Finally, the shear failure test of RB was conducted, the prototype was failed over 490% of shear strain, and real size RB was failed over 430% of shear strain.

• Journal of the Institute of Convergence Signal Processing
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• v.7 no.4
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• pp.195-200
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• 2006

The conventional discrete circuit for ABS/TCS system was examined and the problems of the system were analyzed by computer simulation. In order to improve the performance of ABS/TCS system, interface IC which has error compensation, comparator and under voltage lock-out circuit was designed and their electrical characteristics were investigated. The voltage regulator was included to compensate the temperature variation in the temperature range from $-20^{\circ}C$ to $120^{\circ}C$ for automobile environment. ABS and brake signal were separated using the duty factor of same frequency or different frequencies. UVLO(Under Voltage Lock-Out) circuit and constant current circuit were applied for the elimination of noise, and protection circuit was applied to cut the excess current off. Layout for IC fabrication was designed to enhance the electrical performance of ABS/TCS system. Layout was consisted of 11 masks, arrayed effectively 8 pads to reduce the current loss. We can see that the result of layout simulation was better than the result of bread board.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.659-662
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• 2004

The microwave dielectric properties of the $0.8Mg_4Ta_2O_9-0.2CaTiO_3$ ceramics with sintering temperature were investigated. All the sample of the $0.8Mg_4Ta_2O_9-0.2CaTiO_3$ ceramics prepared by conventional mixed oxide method and sintered at $1400^{\circ}C-1450^{\circ}C$. According to X-ray diffraction patterns of the $0.8Mg_4Ta_2O_9-0.2CaTiO_3$ ceramics, major phase of the hexagonal $Mg_4Ta_2O_9$ phase were showed. Porosity of the $0.8Mg_4Ta_2O_9-0.2CaTiO_3$ ceramics were reduced with increasing sintering temperature, but the bulk density was increased. In the case of $0.8Mg_4Ta_2O_9-0.2CaTiO_3$ ceramics sintered at $1425^{\circ}C$, dielectric constant, quality factor and temperature coefficient of resonant frequency(TCRF) were 13.69, 63,754GHz and -29.37 $ppm/^{\circ}C$, respectively.