• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.2
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• pp.33-39
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• 2004

Sandblasting has recently been developed into a powder blasting technique for brittle materials. In this study, the machinability of $Si_3N_4$-hBN based machinable ceramics are evaluated for micro - pattern making processes using powder blasting. Material properties of the developed machinable ceramics according to the variation of h-BN contents give a good machinability to the ceramics. The effect of scanning times, the size of patterns and variation of BN contents on the erosion depth of samples without mask and samples with different mask patterns in powder blasting of $Si_3N_4$-hBN ceramics are investigated. The Parameters are the impact angle of $90^{\circ}$, the scanning times of nozzle up to 40, and the stand-off distances of 100mm The widths of masked pattern are 0.1mm 0.5mm and 1mm. The powder used is Alumina particles, WA#600. and the blasting pressure of powder is 0.2MPa. Through required experiments, the results are investigated and analyzed. As the results, the machinability of the developed ceramics increases as the BN contents in the ceramics.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.4
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• pp.288-292
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• 1998

In this paper, we fabricated $SnO_2$ composite ceramics doped with 0~20mol% $SnO_2$ of bulk type to investigate the CO and $H_2$ gas sensitivity in various composition, temperature, and concentration of CO and $H_2$ gas. At the temperature range from $100^{\circ}C\sim425^{\circ}C$, the measured 1000ppm and 250ppm CO gas sensitivities of $SiO_2-SnO_2$composite ceramics were about 1.0~7.6 and 1.0~5.6, respectively. These values were about 1.0~1.5 times larger than pure $SnO_2$. The maximum 1000ppm CO gas sensitivity of $SiO_2-SnO_2$composites were measured around $325^{\circ}C$. At the temperature range from $270^{\circ}C\sim380^{\circ}C$, the 1000ppm and 500ppm $H_2$gas sensitivities of $SiO_2-SnO_2$ composites were about 2.9~21.2 and 2.1~11.3, respectively. Also the maximum 1000, 500 ppm $H_2$ gas sensitivities of samples were measured around.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1274-1276
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• 1993

The silicon-nitride films formed by laser CVD method are used for passivating GaAs surfaces. The electrical Properties of metal-insulator-GaAs structure are studied to determined the interfacial characteristics by C-V curves and deep level transient spectroscopy(DLTS). The SiN films are photolysisly deposited from $SiH_4\;and\;NH_3$ in the range of $100^{\circ}C-300^{\circ}C$ on P type, (100) GaAs. The hysteresis is reduced and interface trap density is lowered to $10^{12}-10^{13}$ at $100^{\circ}C-200^{\circ}C$. The surface leakage current is studied too. The passivated GaAs have a little leakage current compared to non passivated GaAs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.131-131
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• 2008

Silicon carbide (SiC) has attracted significant attention for high frequency, high temperature and high power devices due to its superior properties such as the large band gap, high breakdown electric field, high saturation velocity and high thermal conductivity. We performed Al ion implantation processes on n-type 4H-SiC substrate using a SILVACO ATHENA numerical simulator. The ion implantation model used a Monte-Carlo method. We studied the effect of channeling by Al implantation simulation in both 0 off-axis and 8 off-axis n-type 4H-SiC substrate. We have investigated the Al distribution in 4H-SiC through the variation of the implantation energies and the corresponding ratio of the doses. The implantation energies controlled 40, 60, 80, 100 and 120 keV and the implantation doses varied from $2\times10^{14}$ to $1\times10^{15}cm^{-2}$. In the simulation results, the Al ion distribution was deeper as increasing implantation energy and the doping level increased as increasing implantation doses. After the post-implantation annealing, the electrical properties of Al-implanted p-n junction diode were investigated by SILV ACO ATLAS numerical simulator.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.38.1-38.1
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• 2011

최근 중동정세의 변화와 유류 소비의 증가에 따른 유가의 급등과, 일본 지진사태로 일어난 원자력 발전의 안정성에 대한 문제로 인하여 안전하고 깨끗하게 에너지를 생산할 수 있는, 저탄소 녹색성장을 구현할 수 있는 신재생 에너지에 관련된 연구에 많은 관심이 모아지고 있다. 특히 태양광 에너지를 전기로 변환하여 사용하는 것은 최근 가장 큰 관심사 중 하나이다. 나노결정 Si (nc-Si) 박막은 이러한 광전자 산업 및 태양 에너지 분야에서의 폭넓은 응용 가능성으로 많은 연구가 진행되고 있다. 이러한 nc-Si 박막의 발광 특성은 비정질 박막내 Si 나노결정에 기인한 양자제한효과(quantum confinement effect)에 의한 것으로 알려져 있다. 본 연구에서는 증착시 기판에 AC (alternating current) Bias를 인가하여 PE CVD 기법으로 nc-Si:H 박막을 증착하였다. H2와 SiH4를 각기 45, 20 sccm으로, 100 W의 RF 전압을 주어 플라즈마를 생성하였으며, 60~900 Hz의 주파수 범위에서 60 V의 Bias를 인가하여 박막을 증착하였다. 이들 박막의 결정 크기, 결정화도, 나노 구조 및 광학적, 화학적, 기계적 특성을 XRD, FT-IR, Raman spectroscopey, AFM, PL, Nano indenter 등을 사용하여 조사하였으며, 기판에 인가된 전압과 주파수에 따른 결정크기와 박막의 광학적 특성과 상관관계를 고찰하였다. Bias 전압에 따라 ~1에서 ~4 nm의 크기를 갖는 나노 크리스탈이 생성 되었으며, 최고 10%의 나노결정 분율을 가지는 박막을 증착하였다. 이는 광학적 특성에도 영향을 주어 PL (photoluminescence)의 피크는 470~710 nm의 영역에서 관찰되었다. 또한 AC-Bias의 영향으로 박막 내 응력 해소에도 영향을 주어 박막내 존재하는 응력이 결정에 미치는 영향도 알 수 있었다. 이번 발표에선 증착 조건에 따른 박막의 나노구조 및 광학적 특성의 변화와 이들 간의 상관관계를 발표하고자 한다.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.213-216
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• 2004

This paper describes design and implementation of the 5.5 GHz VCO with parallel-branch inductors using 0.8${\mu}m$ SiGe HBT process technology. The proposed parallel-branch inductor shows $12 \%$ improvement in quality factor in comparison with the conventional inductor. A phase noise of -93 dBc/Hz is measured at 100 kHz offset frequency, and the harmonics in the VCO are suppressed less than -23 dBc. The single-sided output power of the VCO is -6.5$\pm$1.5 dBm. The manufactured VCO consumes 15.0 mA with 2.5 V supply voltage. Its chip areas are 1.8mm ${\times}$ 1.2mm.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.312.2-312.2
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• 2013

태양전지에서 SiNX층은 반사방지막 역할과 표면 페시베이션의 역할을 동시에 하고 있다. SiNx에서 굴절율과 두께는 반사율과 밀접한 관계가 있으며 동시에 표면 소수캐리어 수명에도 큰 영향을 미친다. 따라서 굴절율과 두께를 조절하여 낮은 반사도와 긴 소수캐리어 수명을 가지는 SiNx 박막을 제조하여야 우수한 효율의 태양전지를 제조할 수 있다. 본 연구에서는 다양한 굴절율과 두께의 SiNx 박막을 결정질 실리콘 태양전지에 적용하여 효율과의 상관관계를 해석하였다. SiNx 박막은 PECVD장비를 이용하여 RF파워, 가스혼합량, 증착시간 등을 각각 변화시키며 형성하였다. RF 파워는 100~500 W로 변화 시켰고 혼합가스 변화는 SiH4가스와 NH3가스, Ar가스를 각각 주입하며 증착하였다. RF 파워 300W, 가스혼합량 SiH4 90sccm, NH3 26sccm, Ar 99sccm과 기판 온도 $300^{\circ}C$, 공정시간 58초에서 포면 반사율 1.09%와 굴절률 1.965, 두께 76nm를 갖는 SiNx층을 형성 할 수 있었다. SiNx층을 증착하여 셀을 제작한 결과, 개방전압: 0.612V, 전류밀도: 38.49 mA/cm2, 충실도: 75.62%, 효율: 17.82%를 얻을 수 있었다.

• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.243-249
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• 2014

Three single crystals of fully dehydrated $Co^{2+}$-exchanged zeolite Y (Si/Al = 1.56) were prepared by the exchange of $Na_{75}$-Y ($|Na_{75}|[Si_{117}Al_{75}O_{384}]$-FAU) with aqueous streams 0.05 M in $Co(NO_3)_2$, pH = 5.1, at 294 K for 6 h, 12 h, and 18 h, respectively, followed by vacuum dehydration at 673 K. Their single-crystal structures were determined by synchrotron X-ray diffraction techniques in the cubic space group Fd3m at 100(1) K. They were refined to the final error indices $R_1/wR_2$ = 0.0437/0.1165, 0.0450/0.1228, and 0.0469/0.1278, respectively. Their unit-cell formulas are $|Co_{29.1}Na_{11.8}H_{5.0}|[Si_{117}Al_{75}O_{384}]$-FAU, $|Co_{29.8}Na_{11.0}H_{4.4}|[Si_{117}Al_{75}O_{384}]$-FAU, and $|Co_{30.3}Na_{9.5}H_{4.9}|[Si_{117}Al_{75}O_{384}]$-FAU, respectively. In all three crystals, $Co^{2+}$ ions occupy sites I, I' and II; $Na^+$ ions are also at site II. The tendency of $Co^{2+}$ exchange slightly increases with increasing contact time as $Na^+$ content and the unit cell constant of the zeolite framework decrease.

• Journal of Surface Science and Engineering
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• v.38 no.4
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• pp.174-178
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• 2005

Chemical vapor deposition technique has been used to grow epitaxial SiC thin films on Si wafers using tetramethylsilane(TMS) precursor. The films were observed to grow along (110) direction of 3C-SiC at $800^{\circ}C$. The quality of the films was significantly influenced by the TMS flow rate and growth temperature. Nanocrystal SiC films were grown at flow rates of TMS 10 sccm with $H_2$ carrier gas of 100 sccm. The temperature and gas pressure in the reactor have a great influence on the crystallinity and morphology of the SiC film grown. The growth mechanism of the SiC film on the Si substrate without the carbonization process was discussed based on the experimental results.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2006.05a
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• pp.211-215
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• 2006

평면 광도파로 코어로 사용되는 SiON (Silicon oxynitride)과 클래딩으로 사용되는 $SiO_2$ (Silicon oxide)의 굴절률 차이가 2.5 %인 고굴절률차 평면 광도파로용 SiON 박막을 PECVD (plasma enhanced chemical vapor deposition)로 제작하였다. PECVD에 사용된 가스는 $SiH_4,\;NH_3,\;N_{2}O$이고, Si 기판의 $SiO_2$ 막은 100 nm이다. 가스의 비율에 따라 SiON 막의 굴절률은 633 nm의 파장에서 1.476에서 1.777까지 변화하였다. 코어로 사용되는 SiON의 두께는 $2.5{\mu}m$이고 클래딩과의 굴절률 차이는 2.5 %였다.