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STM에 의한 Dipyridinium 유기분자의 전압-전류 특성 연구
이남석,신훈규,장정수,권영수,Lee, Nam-Suk,Shin, Hoon-Kyu,Chang, Jeong-Soo,Kwon, Young-Soo 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.7
In this study, electrical properties of self-assembled dipyridinium dithioacetate molecule onto the Au(111) substrate is observed using Scanning Tunneling Microscopy(STM) by vortical structure of STM probe. At first, the Au(111) substrate is cleaned by piranha solution$(H_2SO_4:H_2O_2\;=\;3:1)$. Subsequently, 1 mM/ml of dipyridinium dithioacetate molecule is self-assembled onto the Au(111) surface. Using STM, the images of dipyridinium dithioacetate molecule which is self-assembled onto the Au(111) substrate, can be observed. In addition, the electrical properties(I-V) of dipyridinium dithioacetate can also be examined by using Scanning Tunneling Spectroscopy(STS). From the results of the measurement of the current-voltage(I-V), the property of Negative Differential Resistance(NDR) that shows the decreases of current according to the increases of voltage is observed. We found the NDR voltage of the dipyridinium dithioacetate is -1.42 V(negative region) and 1.30 V(positive region), respectively.
된장의 발효숙성에 관여하는 효모의 분포와 가스발생 특성
이남석,오남순 ( Nam Suk Lee,Nam Soon Oh ) 한국응용생명화학회 1996 Applied Biological Chemistry (Appl Biol Chem) Vol.39 No.4
In order to improve the quality of commercially manufactured Doenjang, yeast florae, gas and alcohol formation during fermentation of Doenjang were periodically examined. Candida rugosa, Candida zeylanoides, Pichia farinosa, Saccharomyces cerevisiae and Zygosaccharomyces rouxii were isolated and identified from Doenjang at various fermentation stage. S. cerevisiae and Z. rouxii showed distintive gas and alcohol formation activities and the distribution ratio of Z. rouxii was 26% at 14 days and ?6% as prevailed yeast strain after 30 days fermentation, respectively. Ethanol content of Doenjang was gradually increased into 2.19% at final stage of fermentation. The amount of gas generated during fermentation was 9.75 ㎖/g after 14 days, 4.5 ㎖/g after 30 days and decreased into negligible amount after 45 days fermentation. These inhibitory effects on gas generation by fermentation period would be ascribed to the ethanol produced for fermentation. This results suggest that gas generation in commercially manufactured Doenjang could be eliminated through the effective control of fermentation by yeast without application of any preservatives.
이남석(Nam-suk Lee),양일권(Eal-kuen Yang),박영수(Young-su Park),이상호(Sang-ho Lee) 한국정보과학회 2001 한국정보과학회 학술발표논문집 Vol.28 No.2Ⅲ
기존의 네트워크에서는 새로운 프로토콜을 개발하고 전개한다는 것은 많은 표준화 절차를 요구하고, 관련 응용에서 모든 요구를 네트워크가 수용할 수 없기 때문에 제한적이다. 액티브 네트워크는 네트워크에 프로그래밍이 가능하다는 것으로 새로운 네트워크의 패러다임으로 등장하였다. 액티브 네트워크는 복잡한 구조를 갖고 있고, 보안상으로도 많은 문제점을 갖고 있다. 이 논문에서는 액티브 네트워크의 보안 모델을 소개하고, 보안과 관련된 새로운 옵션을 추가한 패킷모델, 액티브 네트워크의 구조인 실행환경과 노드 운영체제에서의 패킷 처리 과정을 알아본다.
STM/STS 의한 Au(111) 표면에 자기조립된 니트로분자의 전기적 특성 측정
李南錫(Nam-Suk Lee),權寧守(Young-Soo Kwon) 대한전기학회 2006 전기학회논문지C Vol.55 No.1
The characteristic of negative differential resistance(NDR) is decreased current when the applied voltage is increased. The NDR is potentially very useful in molecular electronics device schemes. Here, we investigated the NDR characteristic of self-assembled 4,4'-di(ethynylphenyl)-2'-nitro-1-benzenethiolate, which has been well known as a conducting molecule. Self-assembly monolayers(SAMs) were prepared on Au(111), which had been thermally deposited onto pre-treatment(H₂SO₄:H₂O₂=3:1) Si. The Au substrate was exposed to a 1 mM/l solution of 1-dodecanethiol in ethanol for 24 hours to form a monolayer. After thorough rinsing the sample, it was exposed to a 0.1 μM/1 solution of 4,4' -di(ethynylphenyl)-2'-nitro-1-(thioacetyl)benzene in dimethylformamide(DMF) for 30 min and kept in the dark during immersion to avoid photo-oxidation. After the assembly, the samples were removed from the solutions, rinsed thoroughly with methanol, acetone, and CH₂Cl₂, and finally blown dry with N₂, Under these conditions, we measured electrical properties of self-assembly monolayers(SAMs) using ultra high vacuum scanning tunneling microscopy(UHV-STM). The applied voltages were from -2 V to +2 V with 298 K temperature. The vacuum condition was 6×l0?? Torr. As a result, we found the NDR voltage of the 4,4' -di(ethynylphenyl)-2'-nitro-1-benzenethiolate were -1.61±0.26 V(negative region) and 1.84±0.33 V(positive region), respectively.
STM 탐침과 니트로벤젠 분자 사이의 거리변화에 따른 전기전도 특성 연구
이남석(Nam-Suk Lee),최원석(Won-Suk Choi),장정수(Jeong-Soo Chang),권영수(Young-Soo Kwon) 대한전기학회 2006 대한전기학회 학술대회 논문집 Vol.2006 No.7
본 연구에서는 전도성 분자로 잘 알려진 4,4-Di(ethynyl phenyl)-2'-nitro-1-(thioacetyl)-benzene(nitro-benzene) 분자를 Au (111) 표면에 자기조립하고, ultra high vacuum scanning tunneling microscopy (UHV-STM)을 사용하여 STM tip과 sample 사이의 거리를 변화시키면서 전기전도 특성을 측정하였다. Au 기판제작은 열증착시스템 (Thermal Evaporation System)으로 제작하였으며, piranha 용액 (H₂SO₄ : H₂O₂=3:l)을 사용하여 전치리한 후, 자기조립 단분자막 (SAMs)을 형성하였다. 먼저 1-octanethiol을 ethanol solution용액 1mM/L 농도에서 24시간 동안 자기조립한 후에ethanol를 solution 용액으로 이용하여 nitro-benzene를 0.1mM/L 농도로 암실에서 30분간 자기조립 하였다. 자기조립 후 solution을 제거하기 위해 에탄올로 세척하여 N₂로 건조시켰다. 이 조건하에서 UHV-STM을 사용하여 nitro-benzene SAMs의 실시간 모폴로지의 변화에 따른 nitro-benzene의 전기전도 특성을 STM tip - SAMs - Au 기판의 수직 구조로 STM tip과 nitro-benzene의 거리를 변화시키면서, tunneling current을 조사하였다. 측정 결과 Z-position 변화에 대한 tunneling current 와 resistance의 변화를 확인할 수 있었다.