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IBAD-MgO 기판상에 플라즈마를 이용한 LaMnO<sub>3</sub> 저온 증착
김호섭,오상수,하동우,하홍수,고락길,문승현,Kim, H.S.,Oh, S.S.,Ha, D.W.,Ha, H.S.,Ko, R.K.,Moon, S.H. 한국초전도저온공학회 2012 한국초전도저온공학회논문지 Vol.14 No.1
LMO($LaMnO_3$) buffer layer of superconducting coated conductor was deposited on IBAD-MgO template in the plasma atmosphere at $650^{\circ}C$ which is relatively low compared with conventional deposition temperature of more than $800^{\circ}C$. Deposition method of LMO was DC sputtering, and target and deposition chamber were connected to the cathode and anode respectively. When DC voltage was applied between target and chamber, plasma was formed on the surface of target. The tape substrate was located with the distance of 10 cm between target and tape substrate. When anode bias was connected to the tape substrate, electrons were attracted from plasma in target surface to the tape substrate, and only tape substrate was heated by electron bombardment without heating any other zone. The effect of electron bombardment on the surface of substrate was investigated by increasing bias voltage to the substrate. We found out that the sample of electron bombardment had the effect of surface heating and had good texturing at low controlling temperature.
SmBCO 초전도 선재 특성에 대한 Sm:Ba:Cu 조성비의 영향
김호섭,오상수,장세훈,민창훈,하홍수,하동우,고락길,염도준,문승현,정국채,Kim, H.S.,Oh, S.S.,Jang, S.H.,Min, C.H.,Ha, H.S.,Ha, D.W.,Ko, R.K.,Youm, D.J.,Moon, S.H.,Chung, K.C. 한국초전도학회 2011 Progress in superconductivity Vol.13 No.1
조성경사법을 이용하여 LMO/IBAD-MgO template 상에 EDDC 증착법을 이용하여 $Sm_{1+x}Ba_{2-x}Cu_{3+y}O_{7-d}$ 초전도 박막을 증착하였다. 테이프 형상의 기판상에 길이방향으로 $Sm_{1+x}Ba_{2-x}Cu_{3+y}O_{7-d}$ 박막의 조성비가 연속적으로 변하는 샘플을 얻을 수 있었고, 비접촉 Hallprobe를 이용하여 임계전류를 측정한 결과 조성비에 대응하는 연속적인 임계전류분포를 측정할 수 있었다. 본 조성비 영역 중 Sm:Ba:Cu = 1.01:1.99 :4.87의 조성비에서 최대의 임계전류를 보였다. 이 조성비에서 SmBCO 박막표면에 전체적으로 roof tile 형상의 결정립들이 관찰되었으며 국소적으로 2차상들이 관찰되었다. 조성 경사법을 이용하면 광범위한 조성비영역에서 신뢰도 높은 초전도특성, 결정배향성, 박막표면 형상 등을 조사할 수 있을 것으로 예상된다. The effects of Sm:Ba:Cu composition ratio in SmBCO coated conductor on their superconducting properties were investigated. The SmBCO coated conductors were fabricated by reactive co-evaporation method using EDDC(Evaporation using Drum in Dual Chamber) system. In this system, we could obtain various samples with different composition ratios in a batch by the technique providing composition gradient at deposition zone. From the specimens prepared by EDDC system, we found that composition ratio is uniform parallel to the drum axis, but gradient along the circumferential direction of the drum. We installed a shield having parallelogram open area between the deposition chamber and the evaporation chamber in EDDC system, and attached a 30 cm long template, which is parallel to drum axis, onto the drum surface. In this configuration, we could obtain SmBCO coated conductors having a gradient composition along the length of template. We measured the composition ratios and surface morphologies with periodic interval by SEM and EDAX, and confirmed the profile of composition ratio. We also measured critical current using non-contact Hall probe critical current measurement system and thereby could plot composition ratio vs. critical current. The maximum critical current was obtained, and the surface morphology with the shape of roof tile was observed at the corresponding composition ratio of Sm:Ba:Cu = 1.01:1.99:4.87. It was also found that composition ratio had an effect on not only critical current but also surface morphology.
하홍수,김호겸,고락길,김호섭,송규정,박찬,유상임,주진호,문승현,Ha H. S,Kim H. K,Ko R. K,Kim H. S,Song K. J,Park C,Yoo S. I,Joo J. H,Moon S. H 한국초전도학회 2004 Progress in superconductivity Vol.6 No.1
Ni alloy tape is electropolished to be used as a metal substrate for fabrication of IBAD (ion-Beam Assisted Deposition)-MgO texture template fur HTS coated conductor. Electropolishing is needed to obtain a very smooth surface of Ni alloy tape because the in-plane texture of templates is sensitive to the roughness of metal substrate. The critical current of YBCO coated conductor depends on the texture of YBCO that depends on the texture of the IBAD MgO layer. And so the smoothness of the metal substrate is directly related to the superconducting properties of the coated conductor. In this study, we have prepared a reel-to-reel electropolishing apparatus to polish the Ni alloy tapes for IBAD. Various electropolishing conditions were investigated to improve the surface roughness. Hastelloy tape is continuously electropolished with high polishing current density (0.5 ∼ 2 A/$\textrm{cm}^2$) and fast processing time (1 ∼ 3 min). Polished hastelloy tapes have surface roughness(RMS) of below 1 nm on a 5 ${\times}$ 5 $\mu\m^2$ from AFM and SEM.
Piezo Q - Switched Nd : YAG 레이저에 의한 초미니 전자빔 장치용 Micron - Size Aperture의 레이저 미세가공
안승준(S. J. Ahn),김대욱(D. W. Kim),김호섭(H. S. Kim),최성수(S. S. Choi) 한국진공학회(ASCT) 1999 Applied Science and Convergence Technology Vol.8 No.4(1)
Piezo 방법으로 Q-switched Nd:YAG 레이저를 이용하여 Mo diaphragm을 미세가공하였다. 최근에 이르러 전자빔 리소그라피 분야와 portable 미니 scanning electron microscope (SEM) 분야에 소형화된 전자총 array의 적용이 폭넓게 조사되고 있다. 일반적으로 전자빔 장치제작 기술은 수차를 최소화하는데 있다. 본 연구에서는 piezo Q-switched Nd:YAG 레이저를 이용하여 Mo diaphragm을 미세가공하여 20~30 ㎛의 aperture를 얻었다. Aperture의 정교함과 직경의 크기는 레이저 빔의 에너지, 펄스 폭, 빔의 spot 크기, 그리고 가공물질의 성질에 의존됨을 알았다. Experimental studies of laser micromachining on Mo diaphragm using piezo Q-switched Nd:YAG laser have been performed. Application of miniaturized microcolumn electron gun arrays as a potential electron beam lithography or portable mini-scanning electron microscope (SEM) application have recently extensively examined. The conventional microcolumn fabrication technique would give a limitation on the minimization of aberration. In this paper, we obtained 20~30 ㎛ aperture of laser micro machining on Mo diaphragm using piezo Q-switched Nd:YAG laser. The geometrical figures, such as the diameter and the preciseness of the drilled aperture are dependent upon the total energy of the laser pulse train, laser pulse width, and the diameter of laser spot in addition to the materials-dependent parameters.
저 에너지 초소형 전자칼럼 리소그래피를 이용한 SiO₂ 박막의 Pattern 제작에 관한 연구
요시모토 다카토시(T. Yoshimoto),김호섭(H. S. Kim),김대욱(D. W. Kim),안승준(S. Ahn) 한국자기학회 2007 韓國磁氣學會誌 Vol.17 No.4
Electron beam lithography has been studied as a next-generation lithography technology instead of photo lithography for ULSI semiconductor devices. In this work, we have made a low-energy electron beam lithography system based on the microcolumn and investigated the dependence of the pattern thickness on the energies and dose concentration of the electron beam. We have also demonstrated the potential of low-energy lithography by achieving 100 ㎚-SiO₂ thin film patterning.
WSi<sub>2</sub> word-line 및 bit-line용 spacer-Si<sub>3</sub>N<sub>4</sub> 박막의 증착
안승준,김대욱,김종해,안성준,김영정,김호섭,Ahn S.,Kim D.W.,Kim J.H,Ahn S.J.,Kim Y.J.,Kim H.S. 한국재료학회 2004 한국재료학회지 Vol.14 No.6
$WSi_2$, $TiSi_2$, $CoSi_2$, and $TaSi_2$ are general silicides used today in semiconductor devices. $WSi_2$ thin films have been proposed, studied and used recently in CMOS technology extensively to reduce sheet resistance of polysilicon and $n^{+}$ region. However, there are several serious problems encountered because $WSi_2$ is oxidized and forms a native oxide layer at the interface between $WSi_2$ and $Si_3$$N_4$. In this study, we have introduced 20 $slm-N_2$ gas from top to bottom of the furnace in order to control native oxide films between $WSi_2$ and $Si_3$$N_4$ film. In resulting SEM photographs, we have observed that the native oxide films at the surface of $WSi_2$ film are removed using the long injector system.