• Electronic Materials Letters
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• 제14권6호
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• pp.755-765
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• 2018

In situ nitrogen doped hard carbon nanotubes (NHCNT) were fabricated by pyrolyzing tubular nitrogen doped conjugated microporous polymer. KOH activated NHCNT (K-NHCNT) were also prepared to improve their porous structure. XRD, SEM, TEM, EDS, XPS, Raman spectra, $N_2$ adsorption-desorption, galvanostatic charging-discharge, cyclic voltammetry and EIS were used to characterize the structure and performance of NHCNT and K-NHCNT. XRD and Raman spectra reveal K-NHCNT own a more disorder carbon. SEM indicate that the diameters of K-NHCNT are smaller than that of NHCNT. TEM and EDS further indicate that K-NHCNT are hollow carbon nanotubes with nitrogen uniformly distributed. $N_2$ adsorption-desorption analysis reveals that K-NHCNT have an ultra high specific surface area of $1787.37m^2g^{-1}$, which is much larger than that of NHCNT ($531.98m^2g^{-1}$). K-NHCNT delivers a high reversible capacity of $918mAh\;g^{-1}$ at $0.6A\;g^{-1}$. Even after 350 times cycling, the capacity of K-NHCNT cycled after 350 cycles at $0.6A\;g^{-1}$ is still as high as $591.6mAh\;g^{-1}$. Such outstanding electrochemical performance of the K-NHCNT are clearly attributed by its superior characters, which have great advantages over those commercial available carbon nanotubes ($200-450mAh\;g^{-1}$) not only for its desired electrochemical performance but also for its easily and scaling-up preparation.

• 한국재료학회지
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• 제30권8호
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• pp.383-392
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• 2020

In this paper, AgCl/Ag₃PO₄/diatomite photocatalyst is successfully synthesized by microemulsion method and anion in situ substitution method. X-ray diffraction (XRD), photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and ultraviolet-visible spectroscopy (UV-Vis) are used to study the structural and physicochemical characteristics of the AgCl/Ag₃PO₄/diatomite composite. Using rhodamine B (RhB) as a simulated pollutant, the photocatalytic activity and stability of the AgCl/Ag₃PO₄/diatomite composite under visible light are evaluated. In the AgCl/Ag₃PO₄/diatomite visible light system, RhB is nearly 100 % degraded within 15 minutes. And, after five cycles of operation, the photocatalytic activity of AgCl/Ag₃PO₄/diatomite remains at 95 % of the original level, much higher than that of pure Ag₃PO₄ (40 %). In addition, the mechanism of enhanced catalytic performance is discussed. The high photocatalytic performance of AgCl/Ag₃PO₄/diatomite composites can be attributed to the synergistic effect of Ag₃PO₄, diatomite and AgCl nanoparticles. Free radical trapping experiments are used to show that holes and oxygen are the main active species. This material can quickly react with dye molecules adsorbed on the surface of diatomite to degrade RhB dye to CO₂ and H₂O. Even more remarkably, AgCl/Ag₃PO₄/diatomite can maintain above 95 % photo-degradation activity after five cycles.

• 한국표면공학회지
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• 제29권6호
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• pp.809-815
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• 1996

$Y_2O_3$-based metal-insulator-semiconductor (MIS) structure on p-Si(100) has been studied. Films were prepared by UHV reactive ionized cluster beam deposition (r-ICBD) system. The base pressure of the system was about $1 \times 10^{-9}$ -9/ Torr and the process pressure $2 \times 10^{-5}$ Torr in oxygen ambience. Glancing X-ray diffraction(GXRD) and in-situ reflection high energy electron diffracton(RHEED) analyses were performed to investigate the crystallinity of the films. The results show phase change from amorphous state to crystalline one with increasingqr acceleration voltage and substrate temperature. It is also found that the phase transformation from $Y_2O_3$(111)//Si(100) to $Y_2O_3$(110)//Si(100) in growing directions takes place between $500^{\circ}C$ and $700^{\circ}C$. Especially as acceleration voltage is increased, preferentially oriented crystallinity was increased. Finally under the condition of above substrate temperature $700^{\circ}C$ and acceleration voltage 5kV, the $Y_2O_3$films are found to be grown epitaxially in direction of $Y_2O_3$(1l0)//Si(100) by observation of transmission electron microscope(TEM). Capacitance-voltage and current-voltage measurements were conducted to characterize Al/$Y_2O_3$/Si MIS structure with varying acceleration voltage and substrate temperature. Deposited $Y_2O_3$ films of thickness of nearly 300$\AA$ show that the breakdown field increases to 7~8MV /cm at the same conditon of epitaxial growing. These results also coincide with XPS spectra which indicate better stoichiometric characteristic in the condition of better crystalline one. After oxidation the breakdown field increases to 13MV /cm because the MIS structure contains interface silicon oxide of about 30$\AA$. In this case the dielectric constant of only $Y_2O_3$ layer is found to be $\in$15.6. These results have demonstrated the potential of using yttrium oxide for future VLSI/ULSI gate insulator applications.

• 한국진공학회지
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• 제16권3호
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• pp.197-204
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• 2007

p-형 실리콘 기판 위에 수 ${\AA}$ 두께의 어븀 금속을 증착하고, 후열처리 과정을 통하여 어븀-실리사이드/p-형 실리콘 접합을 형성하였다. 초고진공 자외선 광전자 분광 실험을 통하여 증착한 어븀의 두께에 따라 어븀-실리사이드의 일함수가 4.1 eV까지 급하게 감소하는 것을 관찰하였으며, X-ray 회절 실험에 의하여 형성된 어븀 실리사이드가 주로 $Er_5Si_3$상으로 구성되어 있음을 밝혔다. 또한, 어븀-실리사이드/p-형 실리콘 접합에 알루미늄 전극을 부착하여 쇼트키 다이오드를 제작하고, 전류전압 곡선을 측정하여 쇼트키 장벽의 높이를 산출하였다. 산출된 쇼트키 장벽의 높이는 $0.44{\sim}0.78eV$이었으며 어븀 두께 변화에 따른 상관 관계를 찾기 어려웠다. 그리고 이상적인 쇼트키 접합을 가정하고 이미 측정한 일함수로부터 산출한 쇼트키 장벽의 높이는 전류-전압 곡선으로부터 산출한 값에 크게 벗어났으며, 이는 어븀-실리사이드가 주로 $Er_5Si_3$ 상으로 구성되어 있고, $Er_5Si_3/p-$형 실리콘 계면에 존재하는 고밀도의 계면 상태에 기인한 것으로 사료된다.

• 한국진공학회지
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• 제17권6호
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• pp.518-522
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• 2008

반도체 집적도의 비약적인 발전으로 박막은 더욱 다층화 되고 선폭은 더욱 미세화가 진행되었다. 이러한 악조건에서 소자의 집적도를 계속 향상시키기 위하여 많은 연구가 진행되고 있다. 특히 소자 집적도 향상으로 금속 배선 공정에서는 선폭의 미세화와 배선 길이 증가로 인한 RC지연이 발생하게 되었다. 이를 방지하기 위하여 Al보다 비저항이 작은 Cu를 배선물질로 사용하여야 하며, 또한 일부 공정에서는 이미 사용하고 있다. 그러나 Cu를 금속배선으로 사용하기 위해 해결해야 할 가장 큰 문제점은 저온에서 쉽게 Si기판과 반응하는 문제이다. 현재까지 본 실험실에서는 tungsten (W)을 주 물질로 W-C-N (tungsten- carbon - nitrogen) 확산방지막을 증착하여 연구를 하였으며, $\beta$-ray, XRD, XPS 분석을 통하여 고온에서도 Cu의 확산을 효과적으로 방지한다는 연구 결과를 얻었다. 이 연구에서는 기존 연구에 추가적으로 W-C-N 확산방지막의 표면을 Nano-Indenter System을 이용하여 확산방지막 표면강도 변화를 분석하여 확산방지막의 물성 특성을 연구하였다. 이러한 연구를 통하여 박막내 불순물인 질소가 포함된 박막이 고온 열처리 과정에서 보다 안정적인 표면강도 변화를 나타내는 연구 결과를 얻었으며, 이로부터 박막의 물성 분석을 실시하였다.

• 한국재료학회지
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• 제32권11호
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• pp.496-507
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• 2022

For the selective catalytic reduction of NOx with ammonia (NH₃-SCR), a V₂O₅WO₃/TiO₂ (VW/nTi) catalyst was prepared using V₂O₅ and WO₃ on a nanodispersed TiO₂ (nTi) support by simple impregnation process. The nTi support was dispersed for 0~3 hrs under controlled bead-milling in ethanol. The average particle size (D₅₀) of nTi was reduced from 582 nm to 93 nm depending on the milling time. The NOx activity of these catalysts with maximum temperature shift was influenced by the dispersion of the TiO₂. For the V_0.5W₂/nTi-0h catalyst, prepared with 582 nm nTi-0h before milling, the decomposition temperature with over 94 % NOx conversion had a narrow temperature window, within the range of 365-391 ℃. Similarly, the V_0.5W₂/nTi-2h catalyst, prepared with 107 nm nTi-2h bead-milled for 2hrs, showed a broad temperature window in the range of 358~450 ℃. However, the V_0.5W₂/Ti catalyst (D₅₀ = 2.4 ㎛, aqueous, without milling) was observed at 325-385 ℃. Our results could pave the way for the production of effective NOx decomposition catalysts with a higher temperature range. This approach is also better at facilitating the dispersion on the support material. NH₃-TPD, H₂-TPR, FT-IR, and XPS were used to investigate the role of nTi in the DeNOx catalyst.