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이석관,H. S. Kim,노승정,J. H. Han 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.1
Tritium permeation is one of the critical issues for the economy and safety of fusion power plants. As an initial step in tritium permeation research for fusion reactor applications, experiments were initiated by using hydrogen as a tritium substitute. An experimental system for hydrogen permeation and related behaviors in solid materials was designed and constructed. A continuous flow method was adopted with a capacity for high temperatures up to ¡1,000 ¡É under ultra-high vacuums of ¡10−7 Pa. The hydrogen permeation behavior in SUS 316L stainless steel was investigated in the temperature range from 400 ¡É to 800 ¡É. As a result, the permeability, diffusivity and solubility of hydrogen were determined. The results were compared with the previously existing reference data. Changes in the sample¡¯s surface morphology after the hydrogen permeation experiment are also addressed.
이석관,노승정,S. R. In 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.1
A detailed understanding of the permeation of hydrogen isotopes through structural materials is an important issue concerning the reliability, safety, fuelling and environmental impact of fusion power reactors. The permeation of hydrogen through SUS 316L stainless steel, which will be used in various parts of fusion power reactors, was investigated at an elevated temperature of 800 ℃. From experiments at different hydrogen feed pressures of 0.8, 1.0, 1.5, and 2.0 bar with a 3-mm-thick membrane coupon, the hydrogen pressure exponent was determined, and the rate-limiting step for the permeation was determined to be bulk diffusion. From experiments using membranes of various thicknesses of 1, 2, and 3 mm at 1 bar, the effect of the membrane thickness on the hydrogen permeation was studied and discussed in relation to the bulk diffusion process. The results and the discussions for the hydrogen permeation experiments are presented here.
MOS소자에 대한 1 MeV 전자와 1 MeV 양성자의 Total Ionizing Dose 효과
김희수,이석관,노승정 한국물리학회 2003 새물리 Vol.47 No.6
Total ionizing dose effects on MOS devices have been studied as a function of the irradiation dose. NMOS and PMOS devices with an 85-\AA~ gate oxide thickness, a 10 $\mu m$ gate width, and a 5 $\mu m$ gate length were irradiated using 1-MeV electrons and 1-MeV protons with total irradiation doses of 1, 5, 10, 50, 100, and 500 kGy. The changes in the electrical characteristics, such as the threshold voltage, the on-current, and the off-current, were shown to have a similar behaviors for both electron and proton irradiation. However, the changes after electron irradiation were larger than those after proton irradiation. The difference between the two magnitudes is disscussed using the stopping powers of the two particles. 조사량을 변화시켜 가면서 MOS소자에 대한 total ionizing dose 효과를 연구하였다. 산화막의 두께가 85 \AA이고 게이트의 폭과 길이가 각각 10 $\mu m$와 5 $\mu m$ 인 NMOS, PMOS 소자에 에너지가 1 MeV인 전자와 양성자를 조사하였으며, 조사에 따른 흡수선량은 각각 1, 5, 10, 50, 100, 500 kGy이다. 전자와 양성자 조사에 따른 전기적 특성(문턱전압, on-current, off-current 등)변화의 경향은 유사하였으나, 전자빔 조사 후의 변화량의 값이 상대적으로 크게 나타났다. 이를 전자와 양성자가 물질에 대해 갖는 멈춤능력(stopping power)과 연관하여 토의하였다.
Damage in Graphite Tiles Irradiated with Helium Plasmas
김희수,이석관,Y. G. Ohn,노승정,권진중,박준규,H-J. Woo,S-J. Park,정규선,이철의 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.5
Plasma-facing materials in fusion devices are irradiated by a high particle flux from a dense plasma. Graphite tiles, widely used as plasma-facing materials, were irradiated with a helium plasma of a high flux and low energy; the damage in the graphite-tile target was investigated. Changes in the surface morphology were observed from scanning electron microscopy; the electrical conductivity was decreased from four-probe measurement; the intensity of the graphite disorder peak was increased from Raman spectroscopy.
자기제한적 표면반응에 의한 ZnO 박막성장 및 기판온도에 따른 박막특성
이두형,권새롬,이석관,노승정,Lee, D.H.,Kwon, S.R.,Lee, S.K.,Noh, S.J. 한국진공학회 2009 Applied Science and Convergence Technology Vol.18 No.4
ZnO에 대한 박막증착 연구를 위하여 유도결합 플라즈마 원자층박막증착(inductively coupled plasma assisted atomic layer deposition: ICP-ALD) 장치를 제작하고, 장치에 대한 기본 공정조건을 설정하기 위하여 플라즈마를 유도하지 않은 상태에서 p-type Si(100) 기판 위에 ZnO 박막을 증착하는 다양한 실험을 수행하였다. Zn 전구체(precursor)로는 Diethyl zinc [$Zn(C_2H_5)_2$, DEZn]를, 반응가스(reaction gas)로는 $H_2O$를, 캐리어(carrier) 및 퍼지가스(purge gas)로는 Ar을 사용하였다. 기판온도 $150^{\circ}C$에서 DEZn, $H_2O$, Ar의 공급시간을 변화시켜가면서 자기제한적 표면반응(self-limiting surface reaction)에 의한 박막성장조건을 성공적으로 유도하였다. 기판온도를 변화시켜가면서($90{\sim}210^{\circ}C$) 증착실험을 반복하여, 본 장치에 대한 ALD 공정온도(thermal ALD process window)를 확립하고 성장된 ZnO박막에 대한 증착특성, 결정성, 불순물 및 내부조성비등을 조사하였다. ALD 공정온도는 기판온도 $110{\sim}190^{\circ}C$로써 이 구간에서의 박막 평균증착률은 0.29 nm/cycle로 일정하게 나타났다. 기판온도가 높아질수록 결정성이 향상되어 ZnO(002) 피크가 우세하였다. 모든 ALD 공정온도에서 Zn와 O로만 구성된 고순도의 ZnO 박막을 실현하였는데, 온도가 높아질수록 Zn와 O의 비가 1에 근접하며 안정된 hexagonal wurtzite ZnO 구조의 박막이 성장되었다. An inductively coupled plasma assisted atomic layer deposition(ICP-ALD) system has been constructed for the deposition of ZnO thin films, and various experiments of ZnO thin films on p-type Si(100) substrates have been carried out to find the self-limiting reaction conditions for the ICP-ALD system under non-plasma circumstances. Diethyl zinc[$Zn(C_2H_5)_2$, DEZn] was used as the zinc precursor, $H_2O$ as the oxidant, and Ar as the carrier and purge gas. At the substrate temperature of $150^{\circ}C$, atomic layer deposition conditions based on self-limiting surface reaction were successfully obtained by series of experiments through the variation of exposure times for DEZn, $H_2O$, and Ar. ZnO deposition was repeated at different substrate temperatures of $90{\sim}210^{\circ}C$. As a result, the thermal process window(ALD window) for ZnO thin films was observed to be $110{\sim}190^{\circ}C$ and the average growth rate was measured to be constant of 0.29 nm/cycle. Properties of the film's microstructure and composition(Zn, O, etc.) were also studied. As the substrate temperature increases, the crystallinity was improved and ZnO(002) peak became dominant. The films deposited at all temperatures were high purity, and the films deposited at high temperatures had the composition ratio between Zn and O closer to one of a stable hexagonal wurtzite structure.