• 한국전기전자재료학회논문지
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• 제21권8호
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• pp.727-732
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• 2008

In this work, the etch characteristics of $VO_2$ thin films were investigated using inductively coupled plasma (ICP) of $Cl_2/Ar$ gas mixtures. To analyze the plasma characteristics, a quadrupole mass spectrometer (QMS), an optical emission spectroscopy (OES), and a Langmuir probe measuring system were used. The surface reaction of the $VO_2$ thin films was investigated using X-ray photoelectron spectroscopy (XPS). It was found that an increase in Ar fraction in the $Cl_2/Ar$ plasma at fixed gas pressure, input power, and bias power resulted in increasing $VO_2$ etch rate which reached a maximum value of 87.6 nm/min at 70-75 % Ar. It was confirmed that the etch rate of the $VO_2$ films was mainly controlled by the ion flux. On the basis of measuring results, we will discuss possible etching mechanism of $VO_2$ film in the $Cl_2/Ar$ plasma.

• 한국전기전자재료학회논문지
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• 제31권1호
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• pp.29-33
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• 2018

Using a vanadium dioxide ($VO_2$) source, highly pure and amorphous vanadium oxide (VO) thin films were deposited using an e-beam evaporator at room temperature and high vacuum (<$10^{-7}$ Torr). Then, by controlling the post-annealing conditions such as $N_2:O_2$ pressure ratio and annealing time, we could easily synthesize a homogeneous $VO_2$ thin film and also mixed-phase VO thin films, including $VO_2$, $V_2O_5$, $V_3O_7$, $V_5O_9$, and $V_6O_{13}$. The crystallinity and phase of these were characterized by X-ray diffraction, and the surface morphology by FE-SEM. Moreover, the electrical properties and ethanol sensing measurements of the VO thin films were analyzed as a function of temperature. In general, mixed-phases as a self-doping effect have enhanced electrical properties, with a high carrier density and an enhanced response to ethanol. In summary, we developed an easy, scalable, and reproducible fabrication process for VO thin films that is a promising candidate for many potential electrical and optical applications.

• Corrosion Science and Technology
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• 제20권4호
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• pp.183-188
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• 2021

The increasing demand for energy storage in mobile electronic devices and electric vehicles has emphasized the importance of electrochemical energy storage devices such as Li-ion batteries (LIBs) and supercapacitors. For reversible Li storage, alternative anode materials are actively being developed. In this study, we designed and fabricated an Nb₂O₅-Li₃VO₄ composite for use as an anode material in LIBs and hybrid supercapacitors. Nb₂O₅ powders were dissolved into a solution and the precursors were precipitated onto Li₃VO₄ through a simple, low-temperature hydrothermal reaction. The annealing process yielded an Nb₂O₅-Li₃VO₄ composite that was characterized by X-ray diffraction, electron microscopy, and X-ray photoelectron spectroscopy. Electrochemical tests revealed that the Nb₂O₅-Li₃VO₄ composite electrode demonstrated increased capacities of approximately 350 and 140 mAh g^-1 at 0.1 and 5 C, respectively, were maintained up to 1000 cycles. The reversible capacity and rate capability of the composite electrode were enhanced compared to those of pure Nb₂O₅-based electrodes. These results can be attributed to the microstructure design of the synthesized composite material.

• Journal of Ceramic Processing Research
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• 제20권5호
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• pp.484-489
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• 2019

VO2 is an attractive candidate as a transition metal oxide switching material as a selection device for reduction of sneak-path current. We demonstrate deposition of nanoscale VO2 thin films via thermal atomic layer deposition (ALD) with H2O reactant. Using this method, we demonstrate VO2 thin films with high-quality characteristics, including crystallinity, reproducibility using X-ray diffraction, and X-ray photoelectron spectroscopy measurement. We also present a method that can increase uniformity and thin film quality by splitting the pulse cycle into two using scanning electron microscope measurement. We demonstrate an ON / OFF ratio of about 40, which is caused by metal insulator transition (MIT) of VO2 thin film. ALD-deposited VO2 films with high film uniformity can be applied to next-generation nonvolatile memory devices with high density due to their metal-insulator transition characteristic with high current density, fast switching speed, and high ON / OFF ratio.

• 한국컴퓨터정보학회논문지
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• 제14권5호
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• pp.149-156
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• 2009

우리나라 WiBro가 IEEE 802.16e로 국제표준화 되어 수도권부터 WiBro 네트워크 사업을 수행하고 있다. 본 논문에서는 WiBro 네트워크에서 빈번하게 일어나는 메신저 프로그램과 VoIP를 통한 음성 및 화상통화에 대해 도청을 실시하였다. 패킷 수집과 분석기인 와이어샤크를 통해서 패킷의 도청을 실시하고 SIP, H.263, TCP, UDP 프로토콜을 바탕으로 도청자료를 재생한다. 패킷이 위변조 되지 않았다는 무결성을 시간을 기준으로 검증하여 도청된 VoIP 음성 패킷의 복사본의 시간과 패킷의 시간 그리고 X-Lite 통화 기록의 시간이 일치함을 증명하여 무결성을 검증한다. 무결성이 검증된 자료는 밀봉 봉투에 넣어서 수사 자료로서 활용하기 위해 밀봉 후에 수사관의 간인을 실시하여 법정에서의 증거자료로 사용 할 수 있도록 준비한다.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1997년도 Proceedings of the 12th KACG Technical Meeting and the 4th Korea-Japan EMGS (Electronic Materials Growth Symposium)
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• pp.281-287
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• 1997

• 한국재료학회지
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• 제4권6호
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• pp.715-722
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• 1994

"Smart window"에 코팅재료로 쓰이는 thermochromic $Vo_{2}$박막을 전자빔 증착 방법으로 유리 기판위에 증착시켜 $0^{\circ}C$-$90^{\circ}C$ 온도범위에서 가시광 및 근적외선의 투과율을 spectrophotometer로 측정하였다. $300^{\circ}C$의 기판온도와 $400^{\circ}C$ 어닐링 온도가 $VO_{2}$ 박막이 결정화되기 때문인 것으로 확인되었다. 또한, $VO_{2}$박막을 알곤중에서 어닐링하면 500nm이하의 파장에서는 그 투과율이 상당히 낮아지는 것으로 나타났다. W가 5a/0첨가된 $V_{0.95}W_{0.05}O_{2}$박막은 약 $0^{\circ}C$의 천이돈도를 나타내었고 Sn이 0.5a/o $V_{0.995}W_{0.005}O_{2}$박막의 경우에는 $300^{\circ}C$의 기판온도에서 증착한 후 $450^{\circ}C$/5시간 동안 알곤가스 중에서 어닐링하였을때 뚜렷한 thermochromism을 나타내었으며 이 박막의 천이온도는 실용가능한 온도인 약 $25^{\circ}C$로 발견되었으며 약간의 이력곡선이 나타났다.력곡선이 나타났다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2001년도 추계종합학술대회
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• pp.138-141
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• 2001

최근 국내뿐만 아니라, 전 세계적으로 xDSL(x Digital Subscriber Line) 서비스에 대한 관심이 고조되고 있다. 현재 전 세계적으로 상당수의 통신 서비스 업체들이 xDSL 종류의 하나인 ADSL 서비스를 시작했다. 이러한 ADSL의 다음 세대 기술로써 최근 VDSL 서비스가 부각되고 있다. VDSL은 초고속 디지털 가입자 회선으로 xDSL 중에서 가장 속도가 빠른 서비스이다. VDSL은 최근 부각되고 있는 IP Multicasting, VoD, Broadcast video등을 충분히 서비스 할 수 있는 능력을 지녔다. 본 논문에서는 이러한 VDSL 망 구조의 설계를 통해 최적의 인터넷 서비스를 제공할 수 있는 환경을 제공하고자 한다.

• 센서학회지
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• 제23권5호
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• pp.337-341
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• 2014

For various additives doped-$VO_2$ critical temperature sensors using the nature of semiconductor to metal transition, the crystallinity, microstructure, and temperature vs. resistance characteristics were systematically investigated. As a starting material of $VO_2$ sensor, vanadium pentoxide ($V_2O_5$) powders were used, and CaO, SrO, $Bi_2O_3$, $TiO_2$, and PbO dopants were used, respectively. The $V_2O_5$ powders with dopants were mixed with a vehicle to form paste. This paste was silk screen-printed on $Al_2O_3$ substrates and then $V_2O_5$-based thick films were heat-treated at $500^{\circ}C$ for 2 hours in $N_2$ gas atmosphere for the reduction to $VO_2$. From X-ray diffraction analysis, $VO_2$ phases for pure $VO_2$, and CaO and SrO-doped $VO_2$ thick films were confirmed and their grain sizes were 0.57 to $0.59{\mu}m$. The on/off resistance ratio of the $VO_2$ sensor in phase transition temperature range was $5.3{\times}10^3$ and that of the 0.5 wt.% CaO-doped $VO_2$ sensor was $5.46{\times}10^3$. The presented critical temperature sensors could be commercialized for fire-protection and control systems.

• 생명과학회지
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• 제19권10호
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• pp.1403-1409
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• 2009

본 연구에서는 중년비만여성을 대상으로 비만의 발생요인으로 예상되는 요인을 이용하여 비만의 상태를 연령 척도화하여 비만연령(Obesity Age: OA)이라는 연령 추정식을 산출함과 동시에 비만도(비만연령)를 실제의 역연령과 검토하였고 비만연령의 추정식은 다음과 같다. OAS (Obesity Age Score)=$0.106*X_1+0.035*X_2+0.048*X_3+0.041*X_4+0.003*X_5-0.037*X_6-10.66$ (1) ($X_1$: BMI, $X_2$: 체중, $X_3$: 체지방률, $X_4$: 배둘레, $X_5$: 중성지방, $X_6$: $VO_{2max}$) OA (Obesity Age)=7.3*OAS+49.6*(-1) (2) Z=(CA-49.6)(1-0.03) (3) OAc (Obesity Age corrected)=1.03*CA-7.3*OAS+1.47 (4) 그리고 역연령과 추정된 비만연령(Obesity Age corrected: OAc)의 비교에서는 유의한 차이를 나타내지 않아 타당성이 확인되었으며, 총 6개의 측정항목으로 구성된 비만연령을 통해 비만자 개개인의 비만건강도(상태)를 용이하게 평가할 수 있을 것으로 기대하며, 추후에는 다른 집단에서의 적용가능 여부를 알아보기 위해 교차타당성을 검토해야할 것이라고 사료된다.