• 한국정보전자통신기술학회논문지
• /
• 제9권6호
• /
• pp.534-538
• /
• 2016

This paper discusses the characteristics and effects of dielectric inner-supports on discone antenna for broadband RF test chamber, and the verification has been performed by simulation. Several design parameters such as the thickness of the gap support, the position of the side support, and the thickness of the side support has been analyzed. The thickness of the gap support affected the reflection coefficient. An effect of the offset of the side support from the center was slight below 3 GHz and significant above 3 GHz. The thickness of the side support did not affect the reflection coefficient or the gain much. The performance of the fabricated discone antenna was in good agreement with the simulated results. This investigation of a dielectric support effects could be used to design a commercial discone antenna for broadband RF test chamber, focusing on electrical performance and mechanical stability.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2011년도 제40회 동계학술대회 초록집
• /
• pp.204-205
• /
• 2011

In thin film silicon solar cells, p-i-n structure is adopted instead of p/n junction structure as in wafer-based Si solar cells. PECVD is a most widely used thin film deposition process for a-Si:H or ${\mu}c$-Si:H solar cells. For best performance of thin film silicon solar cell, the dopant profiles at p/i and i/n interfaces need to be as sharp as possible. The sharpness of dopant profiles can easily achieved when using multi-chamber PECVD equipment, in which each layer is deposited in separate chamber. However, in a single-chamber PECVD system, doped and intrinsic layers are deposited in one plasma chamber, which inevitably impedes sharp dopant profiles at the interfaces due to the contamination from previous deposition process. The cross-contamination between layers is a serious drawback of a single-chamber PECVD system in spite of the advantage of lower initial investment cost for the equipment. In order to resolve the cross-contamination problem in single-chamber PECVD systems, flushing method of the chamber with NH3 gas or water vapor after doped layer deposition process has been used. In this study, a new plasma process to solve the cross-contamination problem in a single-chamber PECVD system was suggested. A single-chamber VHF-PECVD system was used for superstrate type p-i-n a-Si:H solar cell manufacturing on Asahi-type U FTO glass. A 80 MHz and 20 watts of pulsed RF power was applied to the parallel plate RF cathode at the frequency of 10 kHz and 80% duty ratio. A mixture gas of Ar, H2 and SiH4 was used for i-layer deposition and the deposition pressure was 0.4 Torr. For p and n layer deposition, B2H6 and PH3 was used as doping gas, respectively. The deposition temperature was $250^{\circ}C$ and the total p-i-n layer thickness was about $3500{\AA}$. In order to remove the deposited B inside of the vacuum chamber during p-layer deposition, a high pulsed RF power of about 80 W was applied right after p-layer deposition without SiH4 gas, which is followed by i-layer and n-layer deposition. Finally, Ag was deposited as top electrode. The best initial solar cell efficiency of 9.5 % for test cell area of 0.2 $cm^2$ could be achieved by applying the in-situ plasma cleaning method. The dependence on RF power and treatment time was investigated along with the SIMS analysis of the p-i interface for boron profiles.

• 항공우주기술
• /
• 제6권2호
• /
• pp.52-59
• /
• 2007

통신위성 (RF 탑재체 위성)은 고효율 및 고이득 반사경 안테나를 포함하는 통신 탑재체 시스템과 버스 시스템으로 구성되어 있어, 이들 시스템에 대한 RF 특성 검증시험은 발사 전에 이루어져야 한다. 일반적으로 통신위성용 안테나의 복사패턴은 원거리 조건을 충분히 만족할 수 있는 테스트 레인지에서 측정된다. 통신위성용 안테나의 복사패턴을 정밀하게 측정하기 위한 테스트 레인지는 급전점과 관측점 사이의 거리가 수십에서 수천 킬로미터까지 필요하다. 급전점과 관측점 사이의 거리가 먼경우, 외부의 복잡한 RF (radio frequency) 환경에 노출되어 정밀한 측정이 어렵게 되고, 기후의 변화에 따른 측정의 제약을 갖게 된다. 이러한 문제점을 고려하여 외부환경으로부터 영향을 받지 않는 안테나 테스트 레인지가 요구된다. 본 논문에서는 현재 진행되고 있는 통신해양기상위성을 비롯하여 앞으로 개발하게 될 통신위성 시스템의 탑재 안테나 및 RF 성능시험을 수행하기 위한 안테나 테스트 레인지의 구성과 레인지 오차 및 평면파의 생성원리를 고찰하구 정밀측정에 부합되는 전파무향실의 설계와 이에 따른 성능 파라미터를 제시하고자 한다.

• 한국진공학회지
• /
• 제15권3호
• /
• pp.314-324
• /
• 2006

KSTAR ICRF 안테나의 진공특성을 실험적으로 조사하였다. 제작된 안테나를 총 유효배기속도 1015 l/s의 진공펌프가 장착된 시험용 진공용기에 설치하였으며, 고주파 시험하기 전에 시간에 따른 압력 변화, 총기체 부하, 도달 진공도 등을 측정하였다. 낮은 출력의 고주파를 반복적으로 인가함으로서 세정 효과를 확인하였다. 안테나에 고주파를 인가하여 시험하는 동안 진공도 변화를 측정하였으며, 압력 상승에 의해 방전이 유발되는 한계 압력을 조사하였다. 본 안테나의 경우 고주파 인가 중에 진공용기의 압력이 $10^{-4}$ mbar 이상이 되면 방전이 일어났다. 장펄스 시험에서 안테나의 온도와 시험용 진공용기의 압력을 측정하여 안테나를 냉각하지 않은 상태에서 운전이 가능한 전압을 조사하였으며, 냉각했을 때의 결과와 비교하였다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
• /
• pp.241.1-241.1
• /
• 2014

The large-area high-power radio-frequency (RF) driven ion sources based on the negative hydrogen (deuterium) ion beam extraction are the major components of neutral beam injection (NBI) systems in future large-scale fusion devices such as an ITER and DEMO. Positive hydrogen (deuterium) RF ion sources were the major components of the second NBI system on ASDEX-U tokamak. A test large-area high-power RF ion source (LAHP-RaFIS) has been developed for steady-state operation at the Korea Atomic Energy Research Institute (KAERI) to extract the positive ions, which can be used for the NBI heating and current drive systems in the present fusion devices, and to extract the negative ions for negative ion-based plasma heating and for future fusion devices such as a Fusion Neutron Source and Korea-DEMO. The test RF ion source consists of a driver region, including a helical antenna and a discharge chamber, and an expansion region. RF power can be transferred at up to 10 kW with a fixed frequency of 2 MHz through an optimized RF matching system. An actively water-cooled Faraday shield is located inside the driver region of the ion source for the stable and steady-state operations of RF discharge. The characteristics and uniformities of the plasma parameter in the RF ion source were measured at the lowest area of the expansion bucket using two RF-compensated electrostatic probes along the direction of the short- and long-dimensions of the expansion region. The plasma parameters in the expansion region were characterized by the variation of loaded RF power (voltage) and filling gas pressure.

• 한국재료학회지
• /
• 제21권3호
• /
• pp.149-155
• /
• 2011

We investigated tribological characteristics of diamond-like carbon (DLC) in a condition with carbon nanotube (CNT) content of 1wt% in aqueous solution. Si-DLC films were deposited by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) process on Al6061 aluminum alloy. In this study, the deposition of DLC films was carried out in vacuum with a chamber pressure of 10-5 to 10-3 Torr achieved by mechanical pump followed by turbo molecular pump. The surface adsorbed oxygen on the Aluminum substrates was removed by passing Ar gas for 10 minutes. The RF power was maintained at 500W throughout the experiment. A buffer layer of HMDSO was deposited on the substrate to improve the adhesion of DLC coating. At this point CH4 gas was introduced in the chamber using gas flow controller and DLC coating was deposited on the buffer layer along with HMDSO for 50 min. The thickness of 1 ${\mu}m$ was obtained for DLC films on aluminum substrates The tribological properties of as synthesized DLC films were analyzed by wear test in the presence of dry air, water and lubricant such as CNT ink.

• 한국재료학회지
• /
• 제15권10호
• /
• pp.621-625
• /
• 2005

Effects of rf power, pressure, sputtering gas composition, and substrate temperature on the deposition rate of the $WC_x$ coatings were investigated. The effects of rf power and sputtering gas composition on the hardness and corrosion resistance of the $WC_x$ coatings deposited by reactive sputtering were also investigated. X-ray diffraction (XRD) and Auger electron spectroscopy (AES) analyses were performed to determine the structures and compositions of the films, respectively. The hardnesses of the films were investigated using a nanoindenter, scanning electron microscopy, ana a salt-spray test, respectively. The deposition rate of the films was proportional to rf power and inversely proportional to the $CH_4$ content of $Ar/CH_4$ sputtering gas. The deposition rate linearly increased with increasing chamber pressure. The hardness of the $WC_x$ coatings Increased as rf power increased. The highest hardness was obtained at a $Ar/CH_4$ concentration of $10 vol.\%$ in the sputtering gas. The hardness of the $WC_x$ film deposited under optimal conditions was found to be much higher than that of the electroplated chromium film, although the corrosion resistance of the former was slightly lower than that of the latter.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
• /
• pp.144-145
• /
• 2006

ZnO is a promising material to make high efficiency violet or blue light emitting diodes (LEDs) for its large binding energy (60meV) and big bandgap. But the high quality p-type conduction of ZnO is a dilemma to achieve LEDs with it. In present study, we presented a reliable method to prepare ZnO thin films on (100)silicon substrates by RF magnetron sputtering in the mixture ambient of $N_2$ and $O_2$, accompanying with low pressure annealing in the sputtering chamber in $O_2$ at $600^{\circ}C$ and $800^{\circ}C$ respectively. X-ray diffraction and Hail effect with Van der Paul method were performed to test ZnO films. Seeback effect was also carried out to identify carrier types in ZnO films and showed the N-doped ZnO film annealed at $800^{\circ}C$ had achieved p-type conduction.

• 항공우주산업기술동향
• /
• 제8권1호
• /
• pp.55-61
• /
• 2010

우주환경은 고진공 환경과 태양 복사열에 의한 고온 환경 및 극저온이 반복되는 가혹한 환경으로, 위성체는 지상에서 발사되어 우주궤도에 진입한 순간부터 이러한 우주환경에 노출되어 위성체의 주요부품에 기능장애가 발생하고 결국 임무의 실패로 이어지기도 한다. 따라서 위성체는 지상에서 우주환경시험을 거쳐 기능 및 작동상태를 점검해야 한다. 한국항공우주연구원에서는 정지궤도 위성과 같은 대형 위성체의 시험을 위해 ${\phi}8m{\times}L10m $급의 대형열진공챔버를 국산화 제작하였다. 대형챔버 내부에서 우주환경시험을 수행하기 위해서는 각종 EGSE cable의 연결, MLI 도포 및 대형 챔버 내부에 대한 접근이 필요하다. 대형열진공챔버는 위성체의 크기에 비해 매우 큰 진공용기로 실제 작업시 위성체에의 접근이 용이하지 않다. 이에 대형열진공챔버 내부에서 위성체 및 챔버 내부 접근의 용이성을 제공하는 전용 치구의 필요성이 대두되어 이를 설계하고자 하며, 본 논문은 access fixture라 불리는 전용치구의 설계 과정에 대해 설명한다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2009년도 하계학술대회 논문집
• /
• pp.74-74
• /
• 2009

Titanium nitride has been used as hardmask for semiconductor process, capacitor of MIM type and diffusion barrier of DRAM, due to it's low resistivity, thermodynamic stability and diffusion coefficient. Characteristics of the TiN film are high intensity and chemical stability. The TiN film also has compatibility with high-k material. This study is an experimental test for better condition of TiN film etching process. The etch rate of TiN film was investigated about etching in $BCl_3/Ar/O_2$ plasma using the inductively coupled plasma (ICP) etching system. The base condition were 4 sccm $BCl_3$ /16 sccm Ar mixed gas and 500 W the RF power, -50 V the DC bias voltage, 10 mTorr the chamber pressure and $40\;^{\circ}C$ the substrate temperature. We added $O_2$ gas to give affect etch rate because $O_2$ reacts with photoresist easily. We had changed $O_2$ gas flow rate from 2 sccm to 8 sccm, the RF power from 500 W to 800 W, the DC bias voltage from -50 V to -200 V, the chamber pressure from 5 mTorr to 20 mTorr and the substrate temperature from $20\;^{\circ}C$ to $80\;^{\circ}C$.