• 열처리공학회지
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• 제32권4호
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• pp.155-160
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• 2019

Diamond Like Carbon (DLC) is a metastable form of amorphous carbon that have superior material properties such as high mechanical hardness, chemical inertness, abrasion resistance, and biocompatibility. Furthermore, its material properties can be tuned by additional doping such as nitrogen or boron. However, either pure DLC or doped DLC show poor adhesion property that makes it difficult to apply contact processing technique. Therefore we propose ultrafast laser micromachining which is non-contact precision process without mechanical degradation. In this study, we developed precision machining process of DLC thin film using an ultrafast laser by investigating the process window in terms of laser fluence and laser wavelength. We have also demonstrated various patterns on the film without generating any microcracks and debris.

• 한국전기전자재료학회논문지
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• 제32권2호
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• pp.110-115
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• 2019

$Pb(Sb_{0.5}Nb_{0.5})_x(Zr_{0.51}Ti_{0.49})_{1-x}O_3$ (abbreviation: PSN-PZT) ceramics were synthesized, using conventional bulk ceramic processing technology, with various PSN doping contents. The maximum density of PSN-PZT was 97% of the theoretical density in the samples sintered at $1,250^{\circ}C$. The maximum values of the piezoelectric properties achieved using the conventional processes were: $k_p$ of 0.625, $d_{33}$ of 531 pC/N, and $g_{33}$ of $33mV{\cdot}m/N$. Finally, we fabricated a piezo-speaker with the optimized PSN-PZT ceramics. The SPL of the speaker was measured at a distance of 1 m, with a driving voltage of $40V_{rms}$ in the frequency range of ~300 Hz to 9 kHz. The measured $SPL_{max}$ was at a very high level (95 dB), which was superior in quality in comparison with those of other commercial products.

• 대한기계학회논문집B
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• 제36권10호
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• pp.1019-1023
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• 2012

본 연구에서는 새로운 알루미늄 유도 결정화 공정을 제안하였다. 알루미늄 박막에 직접 3 A의 정전류를 인가하여 $1cm{\times}1cm$ 넓이의 두께 200 nm 비정질 실리콘 박막을 수십 초 내에 결정화하는 방법이다. 결정화된 다결정 실리콘 박막은 520 $cm^{-1}$ 에서의 라만 분광 피크를 통해 확인할 수 있었다. 공정 후, 알루미늄이 식각된 다결정 실리콘 박막은 다공성 구조임을 SEM 을 통하여 확인할 수 있었다. 또 한, 이차이온질량분석(secondary ion mass spectroscopy)에서 알루미늄 농도가 $10^{21}cm^{-3}$으로 헤비 도핑된 것을 확인 할 수 있었으며, 실시간으로 측정된 열화상 카메라의 결과를 통해 결정화는 820 K 근처에서 일어나는 것을 확인할 수 있었다.

• 한국전자파학회논문지
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• 제14권6호
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• pp.558-566
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• 2003

Li$_2$CO$_3$가 첨가된 BiNbO$_4$ 세라믹스를 이용하여 후막 모노폴 안테나를 제작하였다. 그 결과 Li 이온이 Bi, Nb 이온과 결합하여 이온간의 거리를 증가시켰다. 이에 따라 이온 분극량이 증가하여 유전율은 증가하였지만 세라믹 내 격자구조의 왜곡이 심해져 유전손실이 증가하였다. 안테나 특성에 있어서는 유전율 보다는 품질계수(Q)의 영향을 직접적으로 받았다. 대역폭을 측정한 결과 Li$_2$CO$_3$ 첨가에 따른 급격한 품질계수의 저하와 함께 37 %에서 81.7 %까지 증가한 반면 안테나 이득은 -5.5 dBi 에서 -10.03 dBi까지 급격히 감소하였다. 이로 인해 방사패턴은 Li$_2$CO$_3$ 미(未)첨가 시 보다 낮은 dBi 값을 보여 주었다. 특히 무 지향성을 보여야될 x-y면 방사패턴의 경우 격자구조의 왜곡으로 인한 파장의 산란과 공기와 유전체의 경계면에서 높은 유전율 차이로 굴절이 일어나 심하게 왜곡되어 있었다. 그러나 낮은 품질계수(Q)로 인하여 모든 조성 범위에서 1 GHz 이상의 우수한 -10 dB 대역폭 특성을 보여주었다.

• Journal of Electrical Engineering and Technology
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• 제9권6호
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• pp.2070-2078
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• 2014

In this work, the frequency response of gate-all-around (GAA) Ge/GaAs heterojunction tunneling field-effect transistor (TFET) with hetero-gate-dielectric (HGD) and pnpn channel doping profile has been analysed by technology computer-aided design (TCAD) device-circuit mixed-mode simulations, with comparison studies among ppn, pnpn, and HGD pnpn TFET devices. By recursive tracing of voltage transfer curves (VTCs) of a common-source (CS) amplifier based on the HGD pnpn TFET, the operation point (Q-point) was obtained at $V_{DS}=1V$, where the maximum available output swing was acquired without waveform distortion. The slope of VTC of the amplifier was 9.21 V/V (19.4 dB), which mainly resulted from the ponderable direct-current (DC) characteristics of HGD pnpn TFET. Along with the DC performances, frequency response with a small-signal voltage of 10 mV has been closely investigated in terms of voltage gain ($A_v$), unit-gain frequency ($f_{unity}$), and cut-off frequency ($f_T$). The Ge/GaAs HGD pnpn TFET demonstrated $A_v=19.4dB$, $f_{unity}=10THz$, $f_T=0.487$ THz and $f_{max}=18THz$.

• 전자공학회논문지A
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• 제32A권8호
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• pp.153-165
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• 1995

The design procedure of a GaAs/AlGaAs semiconductor matrix optical switch is presented for a simplified tree architecture in the viewpoint of optical loss. A low loss, 0.537 dB/cm, pin type substrate is designed by considering the loss due to imputity doping at 1.3 $\mu$m wavelength. The operating voltage and the device length of a reversed ${\Delta}{\beta}$ electro-optic directional coupler(EODC) swith which is a cross-point device of the 4${\times}$4 matrix optical switch and the bending loss of rib waveguide are caculated as functions of waveguide parameters and bending parameters. There is an optimum bending radius for some waveguide parameters. It is recommened that higher optical confinement conditions such as wide waveguide width and higher rib-height should be chosen for structural parameters of a low loss and a process insensitive 4${\times}$4 matris optical switch. A 4${\times}$4 optical matrix switch which has a 3 dB loss and a 12 volt operating voltage is designed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1703-1706
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• 1996

The purpose of this study is to research and develop polypyrrole(PPy) positive for thin film rechargeable lithium battery. We investigated cyclic voltammetry, AC impedance response and charge/discharge cycling of PPy/SPE/Li cells as a function of temperature. The redox capacity of $PPy/CF_{3}SO_{3}$ film was the most large. The discharge capacity of PPy/SPE/Li cell with $PPy/CF_{3}SO_{3}$ film was higher than those of $PPy/ClO_{4}$ and $PPy/AsF_6$ films at all cycles. The energy density of PPy/SPE/Li cells during 1st cycle was 73, 90 and 101Wh/kg at $25^{\circ}C$, $45^{\circ}C$ and $60^{\circ}C$, respectively. The improvement of energy density is due to reduction of charge-transfer resistance associated doping-undoping process in PPy film with Increasing temperature. $PPy/CF_{3}SO_{3}$ film shows a good property on charge/discharge cycling in PEO-$LiClO_4$-PC-EC electrolyte.

• 공업화학
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• 제25권6호
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• pp.613-618
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• 2014

본 연구에서는 그래핀 옥사이드의 전기적 특성을 향상시키고자 그래핀 옥사이드에 암모니아수 처리를 이용하여 아민화가 이루어진 그래핀 옥사이드를 제조하였다. 그리고, 아민화된 그래핀 옥사이드의 전기적 특성을 평가하고자 이를 필름으로 제조하여 전자파차폐효율을 측정하였다. 암모니아수 처리 농도가 증가함에 따라 그래핀 옥사이드 표면의 질소 관능기가 증가함을 XPS에 의하여 확인하였으며, 또한, 전자파차폐효율 측정 결과 암모니아수 처리된 그래핀 옥사이드의 전자파차폐효율 특성이 우수함을 확인하였다. 21% 암모니아수 농도로 처리한 그래핀 옥사이드는 2950 MHz 이상에서 -5 dB 이상의 전자파차폐효율을 보여주었으며, 이러한 실험 결과들은 질소 관능기가 그래핀 옥사이드 내에 전자전달을 용이하게 하여 흡수되는 전자파 양을 증가시켰기 때문으로 사료된다.

• Journal of Radiation Protection and Research
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• 제28권2호
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• pp.87-95
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• 2003

반도체 검출기의 p+ 층의 도핑 농도, 열처리에 의한 불순물 재분포와 절단면에서의 guard ring 효과를 전산모사하여 최적의 구조와 공전을 설계하고, MCNP코드로 방사선 반응 특성을 분석하였다. 검출기는 반도체 집적회로 공정에서 설계된 공정변수를 적용하여 격자 방향 <100>, $400{\Omega}cm$, n형, Floating-Zone 실리콘 기판에서 제작되었다. 제작된 검출기의 누설전류 밀도는 $0.7nA/cm^2/100{\mu}m$로서 전기적 특성이 우수한 것으로 나타났으며, Cs-137 감마 선원에 의한 $5mR/h{\sim}25R/h$의 조사선량률 범위에서 방사선 반응 특성은 양호한 선형성을 보였다. 본 연구에서 제안된 공정으로 제작된 PIN 반도체 검출기는 개인선량 측정에 사용될 수 있을 것이다.

• 한국환경과학회지
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• 제20권10호
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• pp.1273-1284
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• 2011

The aim of this research was to evaluate the performance of insoluble electrode for the purpose of degradation of Rhodamine B (RhB) and oxidants generation [N,N-Dimethyl-4-nitrosoaniline (RNO, indicator of OH radical), $O_3$, $H_2O_2$, free Cl, $ClO_2$)]. Methods: Four kinds of electrodes were used for comparison: DSA (dimensional stable anode; Pt and JP202 electrode), Pb and boron doping diamond (BDD) electrode. The effect of applied current (0.5~2.5 A), electrolyte type (NaCl, KCl and $Na_2SO_4$) and electrolyte concentration (0.5~3.5 g/L) on the RNO degradation were evaluated. Experimental results showed that the order of RhB removal efficiency lie in: JP202 > Pb > BDD ${\fallingdotseq}$ > Pt. However, when concerned the electric power on maintaining current of 1 A during electrolysis reaction, the order of RhB removal efficiency was changed: JP202 > Pt ${\fallingdotseq}$ Pb > BDD. The total generated oxidants ($H_2O_2$, $O_3$, free Cl, $ClO_2$) concentration of 4 electrodes was Pt (6.04 mg/W) > JP202 (4.81 mg/W) > Pb (3.61 mg/W) > BDD (1.54 mg/W), respectively. JP202 electrode was the best electrode among 4 electrodes from the point of view of performance and energy consumption. Regardless of the type of electrode, RNO removal of NaCl and KCl (chlorine type electrolyte) were higher than that of the $Na_2SO_4$ (sulfuric type electrolyte) RNO removal. Except BDD electrode, RhB degradation and creation tendency of oxidants such as $H_2O_2$, $O_3$, free Cl and $ClO_2$, found that do not match. RNO degradation tendency were considered a simple way to decide the method which is simple it will be able to determinate the electrode where the organic matter decomposition performance is superior. As the added NaCl concentration was increases, the of hydrogen peroxide and ozone concentration increases, and this was thought to increase the quantity of OH radical.