• 한국재료학회지
• /
• 제16권6호
• /
• pp.341-345
• /
• 2006

[ $Ni_2Si$ ] mixed powders were mechanically alloyed by a ball mill and then processed by hot isostatic pressing (HIP) and spark plasma sintering (SPS). In the powder that was mechanically alloyed for 15minutes(MA 15 min), only Ni and Si were observed but in the powder that was mechanically alloyed for 30minutes(MA 30 min), $Ni_2Si$, Ni and Si were mixed together. Some of the MA 15 min powder and MA 30 min powder were processed by HIP under pressure of 150MPa at the temperature of $1000^{\circ}C$ for two hours and some of them were processed by SPS under pressure of 60 MPa at the temperature of $1000^{\circ}C$ for 60 seconds. Both methods completely compounded the powders to $Ni_2Si$. The maximum density of sintered lumps by HIP method was 99.5% and the maximum density of the sintered lump by SPS method was 99.3%. with the hardness of HRc 66 with the hardness of HRc 63. Therefore, the SPS method that can sinter in short time at low cost is considered to be more economical that the HIP method that requires complicated sintering conditions and high cost and the sintering can produce target materials in desired sizes and shapes to be used for thin film.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2000년도 추계학술대회 논문집
• /
• pp.40-44
• /
• 2000

In this paper, since the research on the etching of SrBi$_2$Ta$_2$O$_{9}$ (SBT) thin film was few (specially Cl$_2$-base ), we had studied the surface reaction of SBT thin films using the OES in high density plasma etching as a function of rf power, dc bias voltage, and Cl$_2$(Cl$_2$+Ar) gas mixing ratio. It had been found that the etch rate of SBT thin films appeared to be more affected by the physical sputtering between Ar ions and surface of the SBT compared to the chemical reaction in our previous papers$^{1.2}$ . The change of Cl radical density that is measured by the OES as a function of gas combination showed the change of the etch rate of SBT thin films. Therefore, the chemical reactions between Cl radical in plasma and components of the SBT enhance to increase the etch rates of SBT thin films and these results were confirmed by XPS analysis.

• Journal of the Optical Society of Korea
• /
• 제7권3호
• /
• pp.145-149
• /
• 2003

The anisotropy of electron energy distribution in oxygen plasmas produced by a high intensity laser was investigated by using polarization spectroscopy. An ultra-short pulsed laser with a pulse duration of 66.5 fs and a power density of $1 {\times} 10^17/ W/$\textrm{cm}^2$$ was used. At this power density and pulse duration, the plasma was generated predominantly by optical field ionization. The degree of polarization of OVI 1s$^2$2p$^2$p2- 1s$^2$4d$^2$D$^{0}$ (J = 1/2-3/2 and 3/2-5/2) transition line at 129.92 $\AA$ was measured. O VI 1s$^2$2p$^2$P$^2$ -1s$^2$4s$^2$S$^2$ (J = 1/2-1/2 and 3/2-1/2) transition line at 132.26 $\AA$ was used to calibrate the sensitivity of the optical system. The dependencies of the degree of polarization on the initial gas density and on the laser polarization were investigated. When the laser polarization was changed from a linear to a circular polarization, the degree of polarization was decreased. When the initial gas density was increased, the degree of polarization was decreased.

• 전기전자학회논문지
• /
• 제18권4호
• /
• pp.447-455
• /
• 2014

본 연구에서는 4H-SiC MOSFET의 주요 문제점인 $SiC/SiO_2$ 계면의 특성을 향상시키기 위해 PECVD (plasma enhanced chemical vapor deposition) 공정을 이용하여 n-based 4H-SiC MOS Capacitor를 제작하였다. 건식 산화 공정의 낮은 성장속도, 높은 계면포획 밀도와 $SiO_2$의 낮은 항복전계 등의 문제를 극복하기 위하여 PECVD와 NO어닐링 공정을 사용하여 MOS Capacitor를 제작하였다. 제작이 끝난 후, MOS Capacitor의 계면특성을 hi-lo C-V 측정, I-V 측정 및 SIMS를 이용해 측정하고 평가하였다. 계면의 특성을 건식 산화의 경우와 비교한 결과 20% 감소한 평탄대 전압 변화, 25% 감소한 $SiO_2$ 유효 전하 밀도, 8MV/cm의 증가한 $SiO_2$ 항복전계 및 1.57eV의 유효 에너지 장벽 높이, 전도대 아래로 0.375~0.495eV만큼 떨어져 있는 에너지 영역에서 69.05% 감소한 계면 포획 농도를 확인함으로써 향상된 계면 및 산화막 특성을 얻을 수 있었다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제55권3호
• /
• pp.116-121
• /
• 2006

Most high-k materials are well known not to be etched easily, Some problems such as low etch rate poor sidewall angle, plasma damage, and process complexity were emerged from the high-density DRAM fabrication. Chemical mechanical polishing (CMP) by a damascene process was proposed to pattern this high-k material was polished with some commercial silica slurry as a function of pH variation. Sufficient removal rate with adequate selectivity to realize the pattern mask of tera-ethyl ortho-silicate (TEOS) film for the vertical sidewall angle were obtained. The changes of X-ray diffraction pattern and dielectric constant by CMP process were negligible. The planarization was also achieved for the subsequent multi-level processes. Our new CMP approach will provide a guideline for effective patterning of high-k material by CMP technique.

• Current Applied Physics
• /
• 제18권12호
• /
• pp.1540-1545
• /
• 2018

SiGe alloy is widely used thermoelectric materials for high temperature thermoelectric generator applications. However, its high thermoelectric performance has been thus far realized only in alloys synthesized employing mechanical alloying techniques, which are time-consuming and employ several materials processing steps. In the current study, for the first time, we report an enhanced thermoelectric figure-of-merit (ZT) ~ 1.1 at $900^{\circ}C$ in ntype $Si_{80}Ge_{20}$ nano-alloys, synthesized using a facile and up-scalable methodology consisting of rapid solidification at high optimized cooling rate ${\sim}3.4{\times}10^7K/s$, employing melt spinning followed by spark plasma sintering of the resulting nano-crystalline melt-spun ribbons. This enhancement in ZT > 20% over its bulk counterpart, owes its origin to the nano-crystalline microstructure formed at high cooling rates, which results in crystallite size ~7 nm leading to high density of grain boundaries, which scatter heat-carrying phonons. This abundant scattering resulted in a very low thermal conductivity ${\sim}2.1Wm^{-1}K^{-1}$, which corresponds to ~50% reduction over its bulk counterpart and is amongst the lowest reported thus far in n-type SiGe alloys. The synthesized samples were characterized using X-ray diffraction, scanning electron microscopy and transmission electron microscopy, based on which the enhancement in their thermoelectric performance has been discussed.

• 한국재료학회지
• /
• 제34권6호
• /
• pp.283-290
• /
• 2024

The aggressive scaling of dynamic random-access memory capacitors has increased the need to maintain high capacitance despite the limited physical thickness of electrodes and dielectrics. This makes it essential to use high-k dielectric materials. TiO₂ has a large dielectric constant, ranging from 30~75 in the anatase phase to 90~170 in rutile phase. However, it has significant leakage current due to low energy barriers for electron conduction, which is a critical drawback. Suppressing the leakage current while scaling to achieve an equivalent oxide thickness (EOT) below 0.5 nm is necessary to control the influence of interlayers on capacitor performance. For this, Pt and Ru, with their high work function, can be used instead of a conventional TiN substrate to increase the Schottky barrier height. Additionally, forming rutile-TiO₂ on RuO₂ with excellent lattice compatibility by epitaxial growth can minimize leakage current. Furthermore, plasma-enhanced atomic layer deposition (PEALD) can be used to deposit a uniform thin film with high density and low defects at low temperatures, to reduce the impact of interfacial reactions on electrical properties at high temperatures. In this study, TiO₂ was deposited using PEALD, using substrates of Pt and Ru treated with rapid thermal annealing at 500 and 600 ℃, to compare structural, chemical, and electrical characteristics with reference to a TiN substrate. As a result, leakage current was suppressed to around 10^-6 A/cm² at 1 V, and an EOT at the 0.5 nm level was achieved.

• 분석과학
• /
• 제25권5호
• /
• pp.265-272
• /
• 2012

기존의 Okamoto cavity를 변형시킨 WR-340 도파관을 사용한 cavity를 제작하고 고출력(2.45 GHz, 2 kW)의 헬륨, 질소 및 아르곤 마이크로파 플라즈마(MIP; Microwave Induced Plasma)를 성공적으로 형성시켰다. 플라즈마 생성의 주요한 요인들은 내부전도체의 직경과 내부전도체와 외부전도체간의 간격, 내부전도체 끝과 토치의 위치 등이 있으며 그 중 헬륨 마이크로파 플라즈마에 대하여 cavity의 디자인을 최적화시키고 그 특성을 조사하였다. ICP(Inductively Coupled Plasma)용 mini 토치와 자체 제작한 나선형흐름토치를 비교 연구한 결과, 헬륨 플라즈마 기체 흐름량은 약 25 L/min~30 L/min로서 서로 비슷하였다. 토치 상단부에 석영관을 덧씌워 공기유입을 막은 결과, 340 nm 근처의 NH분자선들이 없어지거나 감소하였다. 플라즈마의 온도 및 전자밀도를 측정한 결과, 4,350 K의 들뜸 온도와 $3.67{\times}10^{11}/cm^3$의 전자밀도를 얻었다. 이 값들은 기존의 다른 마이크로파 플라즈마와 비슷하거나 약간 작은 값이다. 고출력의 플라즈마로서 수용액을 직접 분석하는 것이 가능하였고 현재 Cl의 검출한계는 116 mg/L 수준으로서 아직 분석적인 최적화가 필요한 단계이다.

• 한국진공학회지
• /
• 제14권2호
• /
• pp.84-90
• /
• 2005

분자선에피를 이용한 $In_{0.2}Ga_{0.8}N/GaN$ 이종접합 구조의 에피성장에 미치는 플라즈마의 rf전력의 영향에 대해 고찰하였다. 플라즈마를 발생시키는 rf 전력과 플라즈마 챔버압력의 조건에 따라 성장표면에 도달하는 분자나 원자의 에너지와 flux가 조절되어 에피성장 속도와 물질적 특성을 변화시킨다. 전력이 너무 낮거나 높은 조건에서 표면거칠기와 광특성이 각각 저하된 결과를 보였으며, 적정한 전력인 400W에서 성장한 $In_{0.2}Ga_{0.8}N/GaN$이 종접합 구조에서 날카로운 계면과 강한 photoluminescence 피크를 보였다. 이러한 현상에 대한 원인으로 고에너지 입자들이 성장표면에서 작용하는 기구들인 플라즈마에 의한 탈착과 표면확산, 성장표면의 하부에 주입되는 결함의 발생에 대하여 논하였다.

• 한국세라믹학회지
• /
• 제52권6호
• /
• pp.395-402
• /
• 2015

The suspension plasma spray (SPS) technique has been used to obtain dense $Y_2O_3$ coatings and to overcome the drawbacks of the conventional air plasma spray (APS). SPS uses suspensions containing micrometer or sub-micrometer sized powders dispersed in liquid media. In this study, microstructure developments and mechanical properties have been investigated as functions of particle size of source material and plasma processing parameters such as plasma power and stand-off distance. The microstructure of the coating was found to be highly related to the particle size and the plasma processing parameters, and it was directly reflected in the hardness and the adhesion strength. When fine powder (BET $16.4m^2/g$) was used as a raw material in the suspension, there was, with increasing stand-off distance, a change from a dense structure with a slightly bumpy surface to a porous structure with a cauliflower-like surface. On the other hand, when a coarse powder (BET $2.8m^2/g$) was used, the coating density was lower, with microscopic splats on the surface. Using fine $Y_2O_3$ powders, the coating layer with an optimum short stand-off distance showed a high hardness of approximately 90% of that of sintered $Y_2O_3$ and an adhesion strength several times higher than that of the coating by conventional APS.