7 research outputs found

    Cutting Edge Nanotechnology

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    The main purpose of this book is to describe important issues in various types of devices ranging from conventional transistors (opening chapters of the book) to molecular electronic devices whose fabrication and operation is discussed in the last few chapters of the book. As such, this book can serve as a guide for identifications of important areas of research in micro, nano and molecular electronics. We deeply acknowledge valuable contributions that each of the authors made in writing these excellent chapters

    ํŒจํ„ฐ๋‹๋œ ์ž๊ธฐ ์†Œ์šฉ๋Œ์ด ํ˜•ํƒœ์˜ ๊ฐ•์ž์„ฑ ๊ตฌ์กฐ ๊ฐ„์˜ ๋™์  ์ƒํ˜ธ ์ž‘์šฉ

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    ํ•™์œ„๋…ผ๋ฌธ (๋ฐ•์‚ฌ)-- ์„œ์šธ๋Œ€ํ•™๊ต ๋Œ€ํ•™์› : ์žฌ๋ฃŒ๊ณตํ•™๋ถ€, 2012. 8. ๊น€์ƒ๊ตญ.์ž๊ธฐ ์†Œ์šฉ๋Œ์ด๋Š” ๋งˆ์ดํฌ๋กœ๋ฏธํ„ฐ ์ดํ•˜์˜ ํŒจํ„ฐ๋‹๋œ ๊ฐ•์ž์„ฑ ๊ตฌ์กฐ์ฒด์—์„œ ์•ˆ์ •ํ•œ ์žํ™” ๊ตฌ์กฐ๋กœ ๋ฐ•๋ง‰ ๋ฉด์— ํ‰ํ–‰ํ•˜๋ฉฐ ์†Œ์šฉ๋Œ์ด์™€ ๊ฐ™์€ ํ˜•ํƒœ๋กœ ๋ฐฐ์—ด๋œ ์ˆ˜ํ‰ ์žํ™” ์„ฑ๋ถ„๊ณผ ๊ตฌ์กฐ์ฒด ์ค‘์‹ฌ๋ถ€์— ๋ฐ•๋ง‰ ๋ฉด์— ์ˆ˜์งํ•œ ๋ฐฉํ–ฅ์˜ ์žํ™” ์„ฑ๋ถ„(์†Œ์šฉ๋Œ์ด ํ•ต)์œผ๋กœ ์ด๋ฃจ์–ด์ ธ ์žˆ๋‹ค. ๋…๋ฆฝ๋œ ์›ํŒํ˜• ๋ฐ•๋ง‰์—์„œ, ์™ธ๋ถ€์˜ ํž˜์ด ์ธ๊ฐ€๋˜๋ฉด ์†Œ์šฉ๋Œ์ด ํ•ต์ด ํ‰ํ˜•์ƒํƒœ์˜ ์œ„์น˜๋ฅผ ์ค‘์‹ฌ์œผ๋กœ ํŠน์ • ์ฃผํŒŒ์ˆ˜๋กœ ํšŒ์ „ํ•˜๋Š” ์ž๊ธฐ ์†Œ์šฉ๋Œ์ด์˜ ์›€์ง์ž„์ด ์—ฌ๊ธฐ ๋œ๋‹ค. ๋ณธ ํ•™์œ„ ๋…ผ๋ฌธ์—์„œ๋Š” ์ž๊ธฐ ์†Œ์šฉ๋Œ์ด ์ƒํƒœ์˜ ๊ฐ•์ž์„ฑ ๊ตฌ์กฐ์ฒด ๊ฐ„์˜ ๋™์  ์ƒํ˜ธ์ž‘์šฉ์„ ๋ฏธ์†Œ์ž๊ธฐ ์ „์‚ฐ๋ชจ์‚ฌ, ์ด๋ก  ๊ณ„์‚ฐ, ์‹คํ—˜์„ ํ†ตํ•ด ์‚ดํ”ผ์—ˆ๋‹ค. ๋ฌผ๋ฆฌ์ ์œผ๋กœ ๋ถ„๋ฆฌ๋œ ์›ํŒํ˜• ๋ฐ•๋ง‰ ์‚ฌ์ด์—์„œ ์ž๊ธฐ ์†Œ์šฉ๋Œ์ด ์ค‘์‹ฌ์˜ ๊ฒฐํ•ฉ ๊ฑฐ๋™์„ ์‹œ๊ณต๊ฐ„ ๋ถ„ํ•ด ์ž๊ธฐ ํˆฌ๊ณผ ์—ฐ X-์„  ํ˜„๋ฏธ๊ฒฝ์„ ์ด์šฉํ•ด ๊ด€์ฐฐํ•˜์˜€๋‹ค. ํ•˜๋‚˜์˜ ์›ํŒ์—์„œ์˜ ์ž๊ธฐ์†Œ์šฉ๋Œ์ด ํšŒ์ „์šด๋™์— ์˜ํ•ด ํšŒ์ „ ํ‘œ์œ  ์ž๊ณ„๊ฐ€ ํ˜•์„ฑ๋˜์–ด ๋‹ค๋ฅธ ์›ํŒ์— ์˜ํ–ฅ์„ ๋ผ์นจ์„ ๋ฐํ˜€๋ƒˆ๋‹ค. ๋”๋ถˆ์–ด ๊ทธ์™€ ๊ฐ™์€ ์ƒํ˜ธ ์ž‘์šฉ์„ ๋ฐ”ํƒ•์œผ๋กœ ์—๋„ˆ์ง€/์‹ ํ˜ธ ์ „๋‹ฌ ๋ฐฉ๋ฒ•์„ ์ œ์•ˆํ•˜์˜€๊ณ  ๋™์  ์ƒํ˜ธ์ž‘์šฉ์˜ ๋ฌผ๋ฆฌ์  ์›์ธ์„ ํƒ์‚ฌํ•˜์˜€๋‹ค. ์ด ๋ฉ”์ปค๋‹ˆ์ฆ˜์€ ๋น ๋ฅด๊ณ  ์กฐ์ ˆ ๊ฐ€๋Šฅํ•œ ์—๋„ˆ์ง€ ์ „๋‹ฌ์„ ๊ฐ€๋Šฅํ•˜๊ฒŒ ํ•œ๋‹ค. ์›ํŒ๊ฐ„์˜ ๊ฑฐ๋ฆฌ ๋ฐ ์ƒํ˜ธ์ž‘์šฉ ์„ธ๊ธฐ์— ๋”ฐ๋ผ ์—๋„ˆ์ง€ ์ „๋‹ฌ ์†๋„์˜ ์กฐ์ ˆ์ด ๊ฐ€๋Šฅํ•˜๋ฉฐ ๋‚ฎ์€ ์ž๊ธฐ ๊ฐ์‡  ์ƒ์ˆ˜๋ฅผ ๊ฐ–๋Š” ๋ฌผ์งˆ์„ ์‚ฌ์šฉํ•จ์œผ๋กœ์จ ์‹ ํ˜ธ ์ „๋‹ฌ ์‹œ์˜ ์—๋„ˆ์ง€ ์†์‹ค์„ ์ค„์ผ ์ˆ˜ ์žˆ๋‹ค. ๋˜ํ•œ ๋™์  ์ƒํ˜ธ์ž‘์šฉ์— ๋Œ€ํ•œ ๊ทผ๋ณธ์  ์ดํ•ด๋ฅผ ๋ฐ”ํƒ•์œผ๋กœ ์ž๊ธฐ ์†Œ์šฉ๋Œ์ด ํšŒ์ „์šด๋™์„ ์ด์šฉํ•œ ๋…ผ๋ฆฌ ์—ฐ์‚ฐ์„ ์ œ์‹œ, ๊ตฌํ˜„ํ•˜์˜€๋‹ค. ์ธ์ ‘ํ•œ ์›ํŒ ๊ฐ„์˜ ์ž๊ธฐ ์†Œ์šฉ๋Œ์ด์˜ ํšŒ์ „์šด๋™์— ์˜ํ•œ ์ •๋ณด๋Š” ์ˆ˜ ๋‚˜๋…ธ์ดˆ ์ดํ•˜์˜ ๋น ๋ฅธ ์‹œ๊ฐ„์— ์ „๋‹ฌ๋œ๋‹ค. ๋ณธ ํ•™์œ„ ๋…ผ๋ฌธ์€ ์ž๊ธฐ ์†Œ์šฉ๋Œ์ด ๊ฐ„์˜ ๋™์  ์ƒํ˜ธ ์ž‘์šฉ์— ๋Œ€ํ•œ ๊ธฐ์ดˆ์ ์ธ ์ดํ•ด์™€ ์›ํŒํ˜• ์ž์„ฑ ๋ฐ•๋ง‰ ๊ฐ„์˜ ํ†ต์ œ ๊ฐ€๋Šฅํ•œ ์ •๋ณด ์ „๋‹ฌ ๋ฐ ์ฒ˜๋ฆฌ ๋ฐฉ๋ฒ•์„ ์ œ๊ณตํ•œ๋‹คIn a sub-micrometer-size patterned ferromagnetic structure, the magnetic vortex is in a strongly stable ground state characterized by an in-plane curling magnetization around and an out-of-plane magnetization in the central region. In isolated disks, applied external forces induce vortex excitations, among which a translational mode exists in which the vortex core rotates around its equilibrium position at a characteristic eigenfrequency. This work focused on dynamic interaction between vortex-state ferromagnetic structures, utilizing micromagnetic simulations, analytical calculations, and experiments. Coupled vortex-core gyration in separated disks was observed by employing time and space resolved full-field magnetic transmission soft x-ray microscopy. We found that the vortex gyration of one disk affects that of the other through their respective dynamically rotating stray fields. In addition, energy/signal transfer based on the transfer mechanism having been provided, the details including the fundamentals of the dynamic interaction between magnetic vortices were investigated. This robust mechanism for energy transfer offers the advantages of a fast and tunable transfer rate, which is a function of disk interdistance and interaction strength. The energy loss during gyration-mediated signal transfer is reduced by using magnetic material that has a low damping constant. Based on a fundamental understanding of that dynamic interaction, a logic operation using vortex gyration was demonstrated. Remarkably, the excitation of vortex gyrations and signal transfer between neighboring disks were as fast as a few ns. This work provides a fruitful fundamental understanding of dynamic interaction between magnetic vortices and a robust means of information-signal transport between physically separated magnetic disks.Contents Abstract i List of Tables viii List of Figures ix 1. Introduction 1 2. Research Background 8 2.1 Micromagnetics 8 2.2 Translational mode of magnetic vortex 13 2.3 Interaction between mangnetic vortices 15 3. Sample Design and Fabrication 19 3.1 Thin film deposition 20 3.2 Lithography 25 3.3 Magnetic field strength and distribution 28 4. Magnetic Imaging using Transmission Soft X-ray Microscopy 30 4.1 Magnetic imaging techniques 31 4.2 X-ray magnetic circular dichroism 35 4.3 Full-field magnetic transmission soft x-ray microscopy (MTXM) 38 4.4 Time resolved imaging using pump and probe technique 41 5. Coupled Vortex Cores Oscillation 43 5.1 Sample preparation and experimental setup 45 5.2 Imaging of vortex core oscillation 48 5.3 Dipolar induced vortex core oscillation 53 6. Energy Transfer through Vortex Core Gyration 56 6.1 Coupled oscillator 57 6.2 Experimental observation of dipolar induced vortex gyrations 61 6.3 Energy transfer between two dipolar-coupled vortex oscillators 68 6.4 Normal modes representation of coupled vortex oscillations 74 6.5 Micromagnetic simulation procedure and results 79 6.6 Frequency splitting and energy transfer rate 82 6.7 Dependence on interdistance 83 6.8 Dependence on relative vortex polarization 86 6.9 Energy attenuation 89 6.10 Propagation of gyration in longer chain 92 7. Logic Operation using Vortex State Structures 96 7.1 Design of archetypal XOR logic by simulations 98 7.2 Experimental verification using soft X-ray microscopy 105 7.3 Differential XMCD images of individual disks vortex gyrations 109 7.4 Programmable logic operations 114 7.5 Limitation 118 8. Summary 122 Bibliography Publication List Patent List Presentations in ConferencesDocto

    A study of electron scattering through noise spectroscopy

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    Charge counting statistics (C.S.) of traversing electron in quantum devices like atomic-molecular junctions is sensitive to the local perturbation in the charge field at the contact and in the quantum channels. The first cumulant of C.S. i.e. current-voltage characteristic of such devices has been tool for such investigation since long time. Here we have used the second cumulant i.e. shot noise to study the electron-electron and electron-phonon interaction in the atomic contacts. The shot noise measurement on the Au atomic chain reveals the inelastic scattering in the noise. These signatures can provide vital information on the feedback of the local phonon population on electron transport. The current-voltage characteristic of the ferromagnetic atomic contacts unexpectedly shows zero bias anomalies. This observation is attributed to the interaction of traversing electron with localized magnetic moments within same host species. The observed connection between the Fano factor and the weight of the zero bias anomalies supports the view that the zero bias anomaly originates from spin scattering by localized magnetic moments. However, whether this is true Kondo scattering as suggested by Calvo et al. cannot be stated conclusively from our data. At the end of thesis we have presented a low noise high frequency broadband noise measurement setup suitable for break junction setup.FOMUBL - phd migration 201

    Implementation of multi-CLB designs using quantum-dot cellular automata

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    CMOS scaling is currently facing a technological barrier. Novel technologies are being proposed to keep up with the need for computation power and speed. One of the proposed ideas is the quantum-dot cellular automata (QCA) technology. QCA uses quantum mechanical effects in the device at the molecular scale. QCA systems have the potential for low power, high density, and regularity. This thesis studies QCA devices and uses those devices to build a simple field programmable gate array (FPGA). The FPGA is a combination of multiple configure logical blocks (CLBs) tiled together. Most previous work on this area has focused on fixed logic and programmable interconnect. In contrast, the work at the Rochester Institute of Technology (RIT) has designed and simulated a configurable logic block (CLB) based on look-up tables (LUTs). This thesis presents a simple FPGA that consists of multiple copies of the CLB created by the RIT group. The FPGA is configured to emulate a ripple-carry adder and a bit-serial multiplier. The latency and throughput of both functions are analyzed. We employ a multilevel approach to design specification and simulation. QCADesigner software is used for layout and simulation of an individual CLB. For the FPGA, the high-level HDLQ Verilog library is used. This hybrid approach provides a high degree of confidence in reasonable simulation time
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