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탄소나노튜브_학사졸업논문

제 1 장 서 론Developed the display technology, new display devices have been appeared in our life like LCD (Liquid Crystal Display), PDP (Plasma Display Panel) and OLED (Organic Light-Emitting Diode). Also, in order to improve display devices, scientists have been researching new and better materials like CNT(Carbon Nanotubes), the hollow and nanometer sized tubes composed of graphite carbon. It is the most famous nano-materials, discovered by Sumio Iijima of NEC in 1991. Because it has a lot of good properties such as optical, electrical and mechanical properties, many engineers have been trying to use it as transparent conductive coatings in display. For instance, CNT is a considerable substitution for ITO(Indium Tin Oxide) used as TCO(Transparent Conductive Oxide) in LCD, because Tin is getting expensive by reason of scarcity. In addition to, it is possible to make a “flexible” display, because CNT coatings can maintain their properties under mechanical stress, even after folding it. Even if the electrical and optical properties of CNT are not better than ITO’s, it is expected we can have use flexible displays with CNT in the future.디스플레이 산업의 발달로 인해, 새로운 형태의 제품이 우리의 생활에 속속 등장하고 있다. 예를 들면, LCD (Liquid Crystal Display), PDP (Plasma Display Panel) and OLED (Organic Light-Emitting Diode) 등이 벌써 쉽게 찾아볼 수 있는 제품들이다. 이것들은 기존의 제품과 달리 새로운 재료나 기술을 적용한 제품들이다. 지금도 많은 과학자들은 CNT(Carbon Nanotubes)같은 더 나은 재료들에 대해 연구하고 있다. CNT란, 탄소 6개로 이루어진 육각형 모양이 서로 연결되어 관 모양을 이루고 있고, 지름이 수 나노미터에 불과한 물질이고, 이에 탄소나노튜브라 이름 지어졌다. 이 탄소나노튜브는 1991년 NEC의 이지마 스미오 박사가 발견하였고, 그 이후 연구를 통해, optical, electrical and mechanical 성질들이 탁월하다는 것을 알게 되었다.[2] 이런 좋은 성질들 때문에, 과학자들은 탄소나노튜브를 디스플레이에서 투명전도코팅으로 사용하려고 노력중이다. 예를 들어, CNT는 기존의 대표 투명전도막으로 쓰인 ITO(Indium Tin Oxide)를 대체할 후보로 꼽힌다. 그 이유는, ITO에서 Indium이 현재 거의 고갈상태에 이르렀고, 그에 따라 경제성에 문제가 있기 때문이다. 또한, 주목해야 할 점은, 탄소나노튜브는 mechanical 성질이 굉장히 좋아서, CNT로 만든 thin film을 접더라도, 그 성질을 그대로 간직하고 있다는 점이다.[4] 이를 이용하면 영화에서나 봄직한 "flexible" display를 만들 수 있다. 물론, 현재 ITO와 비교하여 CNT를 이용한 투명전도막의 연구 결과들을 보면, 아직까지는 ITO에 못 미치지만, 가까운 미래에는 CNT가 ITO를 대체할 뿐만 아니라, flexible display도 탄생될 것이라고 예상된다.제 2 장 탄소나노튜브1. 탄소동소체⇒ 탄소나노튜브를 설명하기 이전에 먼저 탄소동소체에 대해 알아야 한다. 그림1을 보면, 탄소동소체로는 우리가 잘 알고 있는 흑연(graphite), 다이아몬드, 버키볼(Bucky ball)로 알려진 풀러린(fullerene), 그리고 탄소나노튜브(Carbon Nanotubes)가 있다. 다이아몬드는 SP3 구조를 가져서, 자유전자가 없기에 전기전도도가 ‘0’에 가까운 절연체이지만, 원자간의 결합이 굉장히 강하여 열전도도는 매우 큰 물질이다. 흑연은 SP2 구조를 이루고 있어, 전기전도도가 같은 층에서는 굉장히 좋지만, 그림을 보면 알 수 있듯이, 층간에는 약한 π결합을 하고 있다. 반면, 풀러린은 SP2 와 SP3 구조가 혼합적으로 구성되어 있다.[8]PAGE PAGE - 14 -

학위논문| 2012.06.13| 22페이지| 3,000원| 조회(735)

탄소나노튜브, 탄소동소체, 탄소나노튜브 정의, 탄소나노튜브 역사, 탄소나노튜브 ..

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유기박막트랜지스터_OTFT(Organic Thin Film Transistor)

1. Introduction of OTFTsOrganic thin film field-effect transistors (OTFTs) are particularly interesting as their fabrication processes are much less complex compared with conventional Si technology, which involves high-temperature and high-vacuum deposition processes and sophisticated photolithographic patterning methods. In general, low-temperature deposition and solution processing can replace the more complicated processes involved in conventional Si technology. In addition, the mechanical flexibility of organic materials makes them naturally compatible with plastic substrates for lightweight and foldable products. Since the report of the first organic field-effect transistor in 1986, there has been great progress in both the materials¨ performance and development of new fabrication techniques. OTFTs have already been demonstrated in applications such as electronic paper, sensors, and memory devices including radio frequency identification cards (RFIDs). Although OTFTs are not meantould ideally be easy to process, mitigating potential fabrication challenges, and have long-term stability for device longevity. This has proven a difficult balance. The organics possessing the best electronic characteristics to date, small molecules such as pentacene (1) and メ-6T (2), are insoluble and therefore difficult to process. Efforts to solubilize these materials have included the incorporation of side chains, such as the addition of alkyl groups to polythiophene polymers (6,7). The size, type, and regioregularity of these groups have been explored extensively, with the goal of electronic property optimization. From these studies, additional insight has also been gained regarding the relationships between morphological characteristics and charge transport. The nature of substituents, chain length, and processing conditions all affect the packing structure in the films, which is reflected in the electronic properties.Clearly, many factors are at play when active materials do noctor film, these processing parameters should be carefully controlled. High mobilities have been reported with several oligomers by optimizing the deposition conditions.Dielectric films are fabricated in a similar manner to the semiconductor layer. Examples of vacuum-deposited dielectrics include silicon dioxide and parylene. An example of a solution-processed dielectric layer is poly-4-vinylphenol (PVP), which is deposited by spincoating and then cross-linked at 200‘C.Patterning is a crucial part of the fabrication of OTFTs. The organic semiconductor must be confined to the channel region to eliminate parasitic leakage and reduce cross-talk in order to achieve better device performance. The drain, source, and gate electrodes need to be patterned with the required feature size depending on the application. Typically, the smaller the distance between the drain and source electrode (channel length), the higher the current output and the faster the transistor switching speed. The followinvalues VG plotted (a) linearly and (b) semilogarithmically; (c) ID versus VG at VD = -2 V.Figure 4(a) shows a typical plot of drain current ID versus drain voltage VD at various gate voltages VG, which corresponds to a device using DH6T as the semiconductor, 3700 A vapor-deposited parylene-C as the gate insulator, aluminum gate, and gold source and drain electrodes. When the gate electrode is biased negatively with respect to the grounded source electrode, DH6T insulatedgate field-effect transistors (IGFETs) operate in the accumulation mode and the accumulated charges are holes. At low VD, ID increases linearly with VD (linear regime) and is approximately determined from the following equation:where L is the channel length, W is the channel width, Ci is the capacitance per unit area of the insulating layer, VT is the threshold voltage, and m is the field-effect mobility. The latter can be calculated in the linear regime from the transconductance,by plotting ID versus VG at a constant l order to measure the I-V curves using probe-station, the pad where the tips contact should be fabricated relatively large. Also, to making fabrication process more simple, Al back gate is deposited easily. The channel lengths between source and drain are different like 10, 20, and 30 um. Depending on channel length, I-V curves and the leakage current could be different.Figure 6 : Mask design for (a) source and drain, (b) channel of pentacene.Procedure of Measurementwe could obtain the I-V curves and results using probe station and Keithley 4200. First, the contact parts of source, drain, and gate should be prepared, and then, we contact the three tips to OTFTs carefully by confirming with the microscope. The I-V curves like these: the plot of drain current ID versus drain voltage VD at various gate voltages VG and the plot of ID versus VG at a constant low VD and equating the value of the slope of this plot to gm.5. ApplicationOrganics have long been attractive for use in electronics .

공학/기술| 2008.12.19| 12페이지| 2,500원| 조회(1,355)

OTFT, 유기박막트랜지스터, pentacene, OTFTs, 유기박막

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MOScapacitor 제작 및 특성 분석 평가A좋아요

1. Purpose of Experiment The principle of operation could be obtained by fabricating MOS capacitor. Also, we analyze and discuss by measuring C-V and I-V characteristics and understand the electrical properties of MOS capacitor. 2. Introduction of MOS capacitor The MOS capacitor consists of a Metal-Oxide-Semiconductor structure as illustrated by Figure 1 Shown is the semiconductor substrate with a thin oxide layer and a top metal contact, referred to as the gate. A second metal layer forms an Ohmic contact to the back of the semiconductor and is called the bulk contact. The structure shown has a p-type substrate. We will refer to this as an n-type MOS or nMOS capacitor since the inversion layer contains electrons. Figure 1 : The structure of MOS capacitor To understand the different bias modes of an MOS capacitor we now consider three different bias voltages. One below the flatband voltage, VFB, a second between the flatband voltage and the threshold voltage, VT, and finally one larger than the threshold voltage. These bias regimes are

공학/기술| 2008.11.27| 7페이지| 1,500원| 조회(1,070)

캐패시터, Capacitor, MOScapacitor, 모스캐패시터, IV cu..

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DRAM과 Flash memory에 관련하여 영어로 정리하였습니다.

< Outline >1. Introduction- Static Random Access Memory (SRAM)- The Dynamic Random Access Memory (DRAM)- The non-volatile Flash Memory cell2. DRAM- The structure of DRAM- Principle of operation of DRAM- Next DRAM cells3. Flash Memory- The structure of Flash Memory- Principle of operation of Flash Memory- Two important effects : hot carrier effects & Fowler-Nordheim tunneling4. Reference1. IntroductionThere are three of the most important types of semiconductor memory cells : the Static Random Access Memory (SRAM), the Dynamic Random Access Memory (DRAM), and the non-volatile Flash Memory cell. Especially, I am going to describe DRAM and Flash memory.There are some differences among them. SRAMs and DRAMs are volatile in the sense that the information is lost if the power supply is removed. However, for flash memories, information is stored indefinitely. For SRAMs, the information is static. It means that as long as the power supply is on, the information is retained. On the other hand, s transistor (MOSFET between the bitline the storage capacitor), the channel is turned ON, and connects the bitline to the MOS storage capacitor. The gate of this capacitor is permanently connected to the power supply voltage VDD(Drain Voltage), thereby creating a potential well under it which tends to be full of inversion electrons for a p-type substrate (Fig. 3a). We apply either 0V to the bitline (generally corresponding to logic “0”), or VDD (corresponding to logic “1”), and the appropriate voltage appears as the substrate potential of the MOS capacitor. For a stored “0” in the cell, the potential appears as the substrate potential of the MOS capacitor. For a stored “0” in the cell, the potential well that is created under the MOS capacitor by the plate voltage is full of inversion charge (Fig. 3b,c). When the wordline voltage is turned low such that the MOS pass transistor is turned off, the inversion charge under the storage capacitor stays the same; this is the stable state of tthe area under the C-V curve. The charge differential that distinguishes the logic “1” and the logic “0” is the difference of areas under the capacitance-voltage curves in the two cases (Fig. 4).When reading the cell, the pass transistor is turned on, and the MOS storage capacitor charge is dumped on the bitline capacitance CB , precharged to VB (=VDD ). The swing of the bitline voltage will clearly depend on the voltage VC stored in the storage cell capacitance CC . As in the case of the SRAM, the change of the bitline voltage depends on the capacitance ratio between the bitline and the cell. To do differential sensing in the case of DRAMs, we do not use two bitlines per cell as for SRAMs. Instead, we compare the bitline voltage for the selected cell with a reference bitline voltage to which is connected a dummy cell whose MOS capacitance, CB , CC and CD in a DRAM are 800fF, 50fF and 20fF, respectively. The voltage differential that is applied to the sense amplifier then becomes (Fig. 7a). Alternatively, we can go up from the substrate by stacking multiple layers of capacitor electrodes to increase the “stacked” capacitor area (Fig. 7b). Other tricks that have been tried are to purposely create a rough polysilicon surface on the capacitor plates to increase the surface area. In the future, alternative materials may be used. For example, the ferroelectrics have much higher dielectric constant than SiO2 and offer larger capacitance without increasing area or reducing thickness. Promising materials include barium strontium titanate and Zirconium oxide.TimePastPresentFutureApproachesScaled DielectricTrench /stacked capacitorAlternate dielectricProblemsTunneling & wearoutFabricationMaterial propertiesFigure SEQ 그림 * ARABIC 6 - Various approaches (past, present and future) of achieving higher DRAM cell capacitance and charge storage density without increasing cell size.Figure SEQ 그림 * ARABIC 7 - Increasing cell capacitance by exploiting the vertiacl dimension3. Flash Mll is considered to have been removed from the floating gate, the cell is considered to have been “erased” into a low VT state or logic “0”.- Two important effects : hot carrier effects & Fowler-Nordheim tunnelingHow do we go about transferring charges into and out of the floating gate? To program the cell, we can use channel hot carrier effects. We apply a high field to both the drain (bitline) and floating gate (wordline) such that the MOSFET is in saturation. The high longitudinal electric field in the pinch-off region accelerates electrons toward the drain and makes them energetic(hot). We maximize such hot carrier effects near the drain pinch-off region in a flash device by making the drain junction somewhat shallower than the source junction (Fig. 9a). This can be achieved by a separate higher energy source implant that is masked in the drain region. If the kinetic energy of electrons is high enough, a few can become hot enough to be scattered into the floating gate. They must su -

자연과학| 2008.05.14| 11페이지| 1,500원| 조회(583)

DRAM, SRAM, Flash memory, Fowler-Nordheim

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탄소나노튜브에 대한 PPT 평가D별로예요

탄소나노튜브 Carbon nanotube목 차탄소나노튜브 탄소동소체 정의, 역사 특성, 형태 벡터표현 합성방법 정제방법 분산방법투명전도막 정의 및 역사 Applications 종류 ITO의 문제점 CNT를 이용 - 연구동향탄소동소체Diamond – SP3 Graphite – SP2 Fullerene – SP2 SP3탄소나노튜브 - 정의탄소동소체로서, 하나의 탄소가 다른 탄소원자와 육각형 벌집무늬로 결합되어 튜브형태를 이루고 있는 물질. 튜브의 직경이 나노미터 수준으로 극히 작은 영역의 물질. 길이는 수 nm에서 mm까지 길어, 길이 대 직경비가 큼.탄소나노튜브Carbon nanotubeRoll upGraphene layer탄소나노튜브 - 역사1985 Kroto와 Smalley - Fullerene(C60)발견 1991 Iijima박사 - 탄소나노튜브 발견 1992 Ebbesen Ajayan - 전기방전법으로 탄소나노튜브 합성 1993 IBM의 Bethune와 Iijima 박사 1nm 수준의 단중벽 나노튜브 합성 1996 Smalley 레이저 증착법 SWNT를 고수율로 성장 1998 Ren 플라즈마 화학기상증착법 Glass위에 고순도의 탄소나노튜브 합성탄소나노튜브 - 특성전기적 특성 열 적 특성 기계적 특성 화학적 특성현존하는 물질 중 결함이 거의 없는 완벽한 신소재탄소나노튜브 – 형태결합수에 따라(1) Single-walled Nanotube(2) Double-walled Nanotube(3) Multi-walled Nanotube탄소나노튜브 – 형태결합수에 따라(4) Rope Carbon Nanotube탄소나노튜브 – 형태(a) MWNT 구조a(c) SWNT 구조 (b), (d) SWNT의 다발 형태탄소나노튜브 – 형태원자 배열 모양에 따라..(a) Armchair (metallic) (c) Chiral (semiconducting) (b) Zigzag (metallic or semiconducting)벡터표현n=m ⇒ metallic n-m=3i ⇒ semi-metallic n-m≠3i ⇒ semiconducting m=0 ⇒ zigzag (metallic or semiconducting) n=m ⇒ armchair (metallic) 그 외 ⇒ chiral (semiconducting)벡터표현n=m ⇒ metallic n-m=3i ⇒ semi-metallic n-m≠3i ⇒ semiconducting m=0 ⇒ zigzag (metallic or semiconducting) n=m ⇒ armchair (metallic) 그 외 ⇒ chiral (semiconducting)벡터표현탄소나노튜브 - 합성방법1) 아크방전법 (electric arc-discharge)Ijima 처음 소개 1st only MWNT and ropes Fe, Co, Ni particles allowed SWNT to grown 다른 합성법에 비해 순도가 낮음탄소나노튜브 - 합성방법2) 레이저 증착법 (Laser vaporization)1995, Smalley SWNT using Co, Ni powder High quality탄소나노튜브 - 합성방법3) 플라즈마 화학기상증착법 (Plasma Enhanced Chemical Vapor Deposition)저온 합성 가능 균일 성장 어려움탄소나노튜브 - 합성방법4) 열 화학기상증착법 (Thermal Chemical Vapor Deposition)High quality 대면적 균일성장 가능 대량합성 가능 고온 필요탄소나노튜브 - 합성방법5) 기상합성법(Vapor Phase Growth)대량합성가능탄소나노튜브 - 정제방법액상 산화법 (liquid-phase oxidation) 기상 산화법 (gas-phase oxidation) 크래마토그래피 (chromatography) 거르기 (filtration)합성 후, 탄소나노튜브 외의 부산물 (탄소함유 물질, 비정질 탄소 및 사용된 전이금속)들을 제거하기 위한 정제 필요.탄소나노튜브 - 분산방법초음파 처리 (sonication) 정전기적 분산 (산처리) 계면활성제 (대표적 SDS)합성 과정에서, 응집현상 발생. 탄소나노튜브의 특성 저하 요인. 분산 문제는 필수 해결과제.[1] Young Hee Lee., Synthesis and Application of Carbon Nanotubes , Carbon Science., vol. 2. No. 2 June 2001 pp. 120-141. [2] 이영희., 탄소나노튜브의 물성과 응용. The Korean Physical Society., vol 51, No. 2 August 2005, pp. 84-144 [3] Axel Schindler, Solution-deposited carbon nanotube layers for flexible display applications, Physica E [4] M.Kaempgen, Transparent carbon nanotube coatings, Applied Surface Science, 252(2005) p. 425-429 [5] L.Hu, D.S.Hecht, and G.GrUner, Percolation in Transparent and Condunting Carbon Nanotube Networks, Nano Letters, vol.4, No.12, 2513-2517 [6] 한국과학기술정보연구원, 탄소나노튜브 분산 기술 (Dispersion of Carbon Nanotube) 2005.4 [7] 이시무, 투명전도막, ㈜금강고려화학 중앙연구소, 2003 [8] 일진나노텍, http://www.iljinnanotech.co.krReference{nameOfApplication=Show}

자연과학| 2008.05.14| 22페이지| 2,000원| 조회(1,932)

CNT, 탄소나노튜브, Carbon Nanotube

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