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Effects of deposition and synthesis parameters on size, density, structure, and field emission properties of Pd-catalyzed carbon nanotubes synthesized by thermal chemical vapor deposition

Journal of Vacuum Science & Technology B: Microelectronics a...

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Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena 2005年第2期23卷 793-799页

作者： S. Wei W. P. Kang W. H. Hofmeister J. L. Davidson Y. M. Wong J. H. Huang Interdisciplinary Program in Materials Science Vanderbilt University Nashville Tennessee 37235 USA Department of Electrical and Computer Engineering Vanderbilt University Box 1661-B Vu Station B Nashville Tennessee 37235 USA Department of Chemical Engineering Vanderbilt University Nashville Tennessee 37235 USA Department of Materials Science and Engineering National Tsing Hua University Hsinchu 300 Taiwan Republic of China

The effects of deposition parameters and NH3 pretreatment on the size and distribution of Pd catalytic particles and subsequently their effects on the characteristics of the synthesized carbon nanotubes (CNTs) were systematically investigated. It was found that the size of Pd particles decreases and the particle density (total number of Pd particles per unit area) increases as the Pd film thickness decreases. Moreover, pretreatment of Pd film in NH3 gas promotes smaller Pd particles and higher particle density which is beneficial for CNT growth. The CNTs were synthesized by thermal chemical vapor deposition at 750 °C using methane (CH4) as the carbon source, and a mixture of Ar/H2 (80 vol %: 20 vol %) as a carrier gas with NH3 serving as a processing reagent. The incorporation of NH3 in CNT synthesis, per the specific pretreatment of catalytic film, has a distinct effect on the size and morphology of CNTs produced. The interrelation between processing, structure and emission behavior of CNTs produced with different synthesis conditions was examined by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and field emission measurements.

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Carbon nanotube growth from Cu–Co alloys for field emission applications

Journal of Vacuum Science & Technology B: Microelectronics a...

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Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena 2004年第3期22卷 1286-1289页

作者： W. Hofmeister W. P. Kang Y. M. Wong J. L. Davidson Interdisciplinary Graduate Program in Material Science Vanderbilt University Nashville Tennessee 37235 Interdisciplinary Graduate Program in Material Science and Department of Electrical Engineering and Computer Science Vanderbilt University Nashville Tennessee 37235 Department of Electrical Engineering and Computer Science Vanderbilt University Nashville Tennessee 37235

We have developed a method of catalyst preparation for carbon nanotube (CNT) growth that uses solid-state diffusion to precipitate Co particles in a Cu matrix and control the size and size distribution of catalyst particles. Copper is an excellent electrical and thermal conductor, and has a small or negligible solubility for Co. Cu–Co alloys of approximately 5 atm% Co were formed in bulk by splat quenching the liquid alloy and on Si substrates by e-beam evaporation of the alloy, sputtering of the alloy, and sputter deposition of thin films of pure Cu and Co. The Co easily precipitates from dilute solutions of Cu–Co with heat treatment. These alloys and films were used to generate uniform distributions of Co precipitates, and CNTs were successfully grown by plasma enhanced chemical vapor deposition (PE-CVD) and thermal CVD on the materials. These alloys can be patterned by photolithography and sputtering in order to grow CNTs in defined locations. Therefore, the technique is amenable to very large scale silicon integration for field emission applications. The results of this work and data from field emission studies are presented herein.

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A proposal for an integrated utilities engineering-Management M.S. program

A proposal for an integrated utilities Engineering-Managemen...

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2004 37th Annual Frontiers of Power Conference

作者： Barnes, Frank S. Fuchs, Ewald F. Tietjen, Jill S. Silverstein, Joann Ko, Hon-Yim Lookabaugh, Tom Brown, Timothy X. Sicker, Douglas C. University of Colorado AAAS IEEE International Engineering Consortium National Academy of Engineering Department of Electrical Engineering LLC McNeil Technologies Board for Girl Scouts Mile Hi Council Georgia Transmission Corporation of Tucker GA ABET Inc. National Council of Examiners for Engineering and Surveying SWE IEEE Power Engineering Society Department of Civil Environmental and Architectural Engineering UCB National Water Research Institute Women in Engineering Program Center of the American West College of Engineering Department of Civil Environmental and Archetectural Engineering University of Colorado Jet Propulsion Laboratory Computer Science Department Interdisciplinary Telecommunications Program University of Colorado Boulder University of Colorado Boulder Electrical Engineering and Interdisciplinary Telecommunications University of Colorado Boulder Department of Computer Science University of Colorado Boulder ITP Laboratory ACM Internet Society Faculty of the Progress and Freedom Foundation Institute for Regulatory Law and Economics Aspen Institute Communications and Society Program CU Computer and Communications Security Center Center for Science and Technology Policy Research Research and Engineering Center for Unmanned Vehicles Electrical and Computer Engineering Civil Environmental and Architectural Engineering

Electric, water, gas and transportation utilities face severe challenges associated with security, quality, availability, reliability and profitability issues. They must solve interrelated system problems with respect to generation of electricity, transportation of fuel, and potable as well as waste water. In the future, engineers and managers of utilities must be well versed in the different disciplines of engineering including electrical civil, mechanical and information technology. The University of Colorado at Boulder addresses this educational opportunity by proposing a novel Integrated Utilities Management program for M.S. candidates who have a solid B.S. background or equivalent in a related discipline. The M.S. program will consist of four interdisciplinary paths dealing with business management and legal topics as they relate to federal and state regulatory issues, as well as agency and people-related leadership issues. The electric utilities option of this program will be centered on three core courses related to electric power generation/transmission and distribution, security and availability, quality and reliability, economics and environmental policy, and utility finance;two elective courses from a group of courses that address nuclear power, waste water, solid waste, telecommunications, renewable energies, data communication, fuels and case studies;and one capstone course consisting of either operations research or the investigation and resolution of a pending utility project such as the right-of-way of transmission lines, specification of new power plants, retrofitting of power plants or their impact on the environment. It is expected that candidates for this MS program will come from universities, from utilities, and from private and public agencies. The MS program can be completed by full- or part time students within one or two years of intensive study, respectively. Courses will be taught both on campus and nationwide via the Center for Advanced

关键词： Public utilities

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The effects of process parameters on size, density, structure, and field emission properties of Pd-catalyzed carbon nanotubes synthesized by thermal chemical vapor deposition

The effects of process parameters on size, density, structur...

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International Conference on Vacuum Nanoelectronics (IVNC)

作者： S. Wei W.P. Kang W.H. Hofmeister J.L. Davidson Y.M. Wong J.H. Huang Interdisciplinary Graduate Program in Material Science Vanderbilt University Nashville TN USA Department of Electrical Engineering and Computer Science Vanderbilt University Nashville TN USA Department of Chemical Engineering Vanderbilt University Nashville TN USA Department of Materials Science and Engineering National Tsing Hua University Hsinchu Taiwan

In this study, various thicknesses of Pd catalytic films were deposited on Ti/Si substrates and pretreated with NH/sub 3/. The effects of catalyst deposition parameters and NH/sub 3/ pretreatment time (0, 1, and 10 minutes) on the size distribution of Pd catalytic particles, and subsequently, on the diameter and density of synthesized carbon nanotubes (CNTs) were investigated. The CNTs were synthesized by thermal CVD at 750/spl deg/C using methane (CH/sub 4/) as the carbon source, and a mixture of Ar/H/sub 2/ (80 vol.%/20 vol.%) as the carrier gas.

关键词： Carbon nanotubes Chemical vapor deposition Argon Hydrogen Scanning electron microscopy Morphology Substrates Materials science and technology Transmission electron microscopy Carbon dioxide

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Carbon nanotube growth from Cu-Co alloys for field emission applications

Carbon nanotube growth from Cu-Co alloys for field emission ...

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IEEE International Conference on Vacuum Microelectronics (IVMC)

作者： W. Hofmeister W.P. Kang Y.M. Wong J.L. Davidson Interdisciplinary Graduate Program in Material Science Vanderbilt University Nashville TN USA Department of Electrical Engineering and Computer Science Vanderbilt University Nashville TN USA

We have used Cu-Co alloy to generate uniform distribution of Co precipitates, and successfully grown CNTs by CVD on the Cu support.

关键词： Carbon nanotubes Conducting materials Transistors Application software Cobalt alloys Copper alloys Materials science and technology Hydrocarbons Chemical vapor deposition Nanocrystals

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On Classifying Daylight for Design

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International Journal of Architectural Computing 2003年第2期1卷 205-217页

作者： Daniel Glaser James Peng Interdisciplinary Doctoral Program University of California at Berkeley Computer Science Division 387 Soda Hall #1776 Berkeley CA 94720 - 1776 USA Department of Electrical Engineering and Computer Sciences University of California at Berkeley Computer Science Division 387 Soda Hall #1776 Berkeley CA 94720 - 1776 USA

In this paper, we present LiQuID, a tool for clustering lighting simulation data. Photographs are useful vehicles for both describing and making assessments of architectural lighting systems. A significant barrier to using photographs during the design process relates to the sheer volume of renderings that needs to be analyzed. Although there have been efforts to produce novel visualization systems to manage large sets of photographs, this research aims to reduce the complexity by classifying data into representative prototypes. A hypothetical case study is discussed.

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Performance of Turbo Trellis-Coded Modulation (T-TCM) on frequency-selective rayleigh fading channels

Performance of Turbo Trellis-Coded Modulation (T-TCM) on fre...

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1999 IEEE International Conference on Communications, ICC 1999

作者： Ha, Nguyen Hoang Rajatheva, R.M.A.P. Department of Electrical and Computer Engineering University of Manitoba WinnipegMBR3T 5V6 Canada Telecommunication Program School of Advanced Technologies Asian Institute of Technology P.O Box 4 Pathumthani12120 Thailand

ISBN: (纸本)078035284X

Turbo Trellis-Coded Modulation (T-TCM) is one of several techniques for combining turbo codes with multilevel modulation in order to save the bandwidth of the transmission systems. T-TCM was shown to perform very well on AWGN channel, but its performance over frequency-selective fading channel is still unknown. In this paper, a system model to investigate the performance of T-TCM schemes over frequency-selective fading channel is proposed. Simulation results show that when appropriate receiver is available, T-TCM also performs well on frequency-selective fading channels. T-TCM performance is much better than any other coded-modulation scheme in the past for this type of channel. © 1999 IEEE.

关键词： Turbo codes

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Performance of turbo trellis-coded modulation (T-TCM) on frequency-selective Rayleigh fading channels

Performance of turbo trellis-coded modulation (T-TCM) on fre...

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IEEE International Conference on Communications (ICC)

作者： Hguye Hoang Ha R.M.A.P. Rajatheva Department of Electrical and Computer Engineering University of Manitoba Winnipeg MAN Canada Telecommunication Program School of Advanced Technologies Asian Institute of Technology Pathum Thani Thailand

Turbo trellis-coded modulation (T-TCM) is one of several techniques for combining turbo codes with multilevel modulation in order to save the bandwidth of the transmission systems. T-TCM was shown to perform very well on AWGN channels, but its performance over frequency-selective fading channels is unknown. In this paper, a system model to investigate the performance of T-TCM schemes over frequency-selective fading channels is proposed. Simulation results show that when an appropriate receiver is available, T-TCM also performs well on frequency-selective fading channels. T-TCM performance is much better than any other coded-modulation scheme for this type of channel.

关键词： Frequency modulation Fading Turbo codes Modulation coding Iterative decoding Bandwidth AWGN channels Bit error rate Filters Iterative algorithms

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Guest Editorial: Focus on Digital Signal Processing Techniques Applied to Space Communications

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European Transactions on telecommunications 1993年第1期4卷 9-10页

作者： Gaudenzi, Riccardo De Elia, Carlo Harris, Robert A. Rimrdo De Gaudend was born in Rosignano Mmo Italy in 1960. He received the Doctor En- gineer degree (cum Laude) in Electronic Engineering from the University of Pisa. Italy in 1985. From 1986 he was with the European Space Agency (ESA). Stsliow and Communications Engineering Department. Darmrtadt (RFA) where he was involved in satellite telecommunication ground systems design and testing. In particular he followed the development of two new ESA's satellite tracking systems. In 1988 be joined the ESA's Research and Technology Centre (ESTEC). Noordwijk. The Netherlands where is holding a position as releeommunication enginm in the Electrical System Department. He is presently responsible for the definition and development of advanced satellite communication systems. His mull intenst b ddyrducd with effacnt digital modulation and access techniques for fued and mobile wtdlite services synchronization topics and communication systems simulation techniques. Carlo Elia (S'89) was born in Trepuzzi. Italy in 1964. He received the Doctor Engineer degree in Electronic Engineering from Politecnico di Torino. Torino. Italy. in 1989. He his now attending a Doctorate program at PolitanieO di Torino. S i 1990. he has been with the Eurpean Space Agency (ESA) in the Electrical System Department as Tdeeommunications Syrtcm Engineer. His main areas of interest are related to rdvanccd digital modulation and access techniques and channel equalization. R.A. (Bob) Harris (S'69–M'70) received the PhD from the University of Southampton. England in 1971. In 1970 he joined the European Space Agency (then ESRO). based at the European Space Research and Technology Centre (ESTEC) Noordwijk. The Netherlandswas working on telemetry and telecommand systems. Since 1978 he has been Head of the Transmision Techniques Section in the Directorate of Telecom munications. He was involved in the transmission design of the OTS ECS Olympus and European Data Relay systems. He has worked on a wide range of analogue and digital transmission topics wit

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An approach to blind equalization of non-minimum phase systems

An approach to blind equalization of non-minimum phase syste...

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International Conference on Acoustics, Speech, and Signal Processing (ICASSP)

作者： W.A. Sethares R.A. Kennedy Z. Gu Department of Electrical and Computer Engineering University of Wisconsin Madison WI USA Department of System Engineering RSPhysSE and Interdisciplinary Engineering Program Faculty of Science Australian National University Canberra ACT Australia

Blind equalization of systems which contain a nonminimum phase component is a difficult task. Minimizing the energy (l/sub 2/ minimization) of the equalizer output (under a fixed tap constraint) cannot be guaranteed to open the eye (to reliably unscramble the message) because it tends to converge to an equalizer setting that contains a reflection of the unstable zeros inside the unit circle. It is shown that, in at least one simple setup involving a mixture of minimum and nonminimum phase elements, an l/sub infinity / minimization of the equalizer output is the appropriate criterion which should be minimized in order to successfully open the eye. Utilizing a finite impulse response equalizer constrained to have a unity coefficient on the center tap, it is shown that for a large enough dimension (depending on the closeness of the zeros of the channel to the unit circle) the eye will be opened. There is no simple (gradient) scheme to exactly implement the l/sub infinity / minimization. The use of a gradient l/sub p/ scheme for large p is proposed.< >

关键词： Blind equalizers Finite impulse response filter Australia Council Information science Predistortion Distortion Cellular neural networks Quadrature amplitude modulation Stability

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