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International Conference on Vacuum Electronics

作者： Vasilios Vlahos Dane D. Morgan John H. Booske University of Wisconsin Madison Madison WI USA 1415 Engineering Dr. Madison WI Department of Materials Science and Engineering University of Wisconsin Madison Madison WI USA Department of Materials Science and Engineering Department of Electrical and Computer Engineering University of Wisconsin-Madison Madison USA Interdisciplinary Materials Science Program

The changes in the work function upon adsorption of coating layers on materials utilized in both field and thermionic emission applications have been investigated computationally within the framework of Density Functional Theory (DFT) [1] as implemented by the Vienna Ab-initio Simulation Package (VASP) [2]. This approach provides valuable information for understanding the origin of the improvement in the emitted current density by monitoring changes in the electronic structure of a material system upon adsorption of surface species. The presence of surface coatings induces changes in the charge density in the surface and sub-surface regions of the substrate, significantly influencing the value of the work function. The origin of the enhanced emission properties of Cesium-Iodide (Csl) coated Carbon-based field emission cathodes [3] as well as Barium-Oxide (Ba-O) Tungsten thermionic cathode systems has been investigated. The former is a promising cathode material system capable of operating under low global electric fields, demonstrating operation lifetimes in excess of one million pulses, and characterized by good shot-to-shot-reproducibility, low levels of outgassing, and no evident plasma formation upon appropriate conditioning.

关键词： Cathodes Coatings Thermionic emission Density functional theory Computational modeling Electronic packaging thermal management Current density Monitoring Tungsten Plasma applications

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Carbon nanostructure field emission devices

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Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures 2006年第2期24卷 1008-1012页

作者： Wong, Y.M. Kang, W.P. Davidson, J.L. Soh, K.L. Choi, B.K. Hofmeister, W. Department of Electrical Engineering and Computer Science Vanderbilt University Nashville TN 37235 Interdisciplinary Graduate Program in Material Science Vanderbilt University Nashville TN 37235 Department of Chemical Engineering Vanderbilt University Nashville TN 37235

The microwave plasma chemical vapor deposition (MPCVD) method is capable of synthesizing various forms of carbon allotropes such as diamond, carbon nanotubes (CNTs), and diamondlike carbon (DLC) while varying the growth parameters or utilizing substrate coated with catalytic thin film. In this article, needlelike carbon nanostructures (CNs) were synthesized utilizing high power (5 kW) and high working pressure (120 Torr) MPCVD on a thin catalytic film of nickel with a diffusion barrier layer of titanium on a micropatterned silicon substrate. The effects of in situ doping by trimethylboron (TMB) on the morphologies and field emission properties of the CNs were also investigated. Straight, needlelike CNs with random orientation were obtained for 15 min growth time with or without TMB doping. However, the CNs appear to transform into diamondlike nanocrystals after prolonged growth of 30 min with TMB doping. Unlike MPCVD grown CNTs, it was found that the CNs have strong adhesion to the substrate and could withstand postgrowth processing such as ultrasonic agitation cleaning in solvents. Field emission tests performed show that in situ TMB doping of the patterned needlelike CNs lowers the turn-on field of the cathode. A vacuum field emission triode with self-aligned gate utilizing CNs as the field emitter is also fabricated. © 2006 American Vacuum Society.

关键词： Carbon nanotubes

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Blank slate engineering at Florida Gulf Coast University - Innovative and multidisciplinary from the ground up

Blank slate engineering at Florida Gulf Coast University - I...

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113th Annual ASEE Conference and Exposition, 2006

作者： Blanchard, Susan Egiebor, Nosa Sweeney, James Zidek, Lisa Sechrist, Chalmers Hulbert, Sam Osborn, James O'Neill, Robert Florida Gulf Coast University United States FGCU School of Engineering Institute of Electrical and Electronics Engineers Biomedical Engineering Society American Institute for Medical and Biological Engineering United Kingdom Department of Environmental and Civil Engineering Arizona State University United States Department of Bioengineering Department of Bioengineering Arizona State University United States Flinn Foundation Funded Multi- and Interdisciplinary Graduate Training Program in Bioengineering Milwaukee School of Engineering United States Graduate Programs Industrial Engineering Program Department of Electrical and Computer Engineering Department of Engineering University of Illinois Urbana-Champaign United States Institute of Electrical and Electronics Engineers Rose-Hulman Institute for Technology School of Engineering FGCU School of Engineering's Advisory Board Roger Williams University United States Department of Civil Engineering Department of Engineering Roger Williams University United States

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MEMS and microsystems courses with national and international dissemination

MEMS and microsystems courses with national and internationa...

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113th Annual ASEE Conference and Exposition, 2006

作者： McAfee, Leo Najafi, Khalil Gianchandani, Yogesh Wise, Kensall D. Maharbiz, Michel M. Aslam, Dean Bergstrom, Paul Friedrich, Craig University of Michigan United States IEEE ASEE Department of Electrical Engineering and Computer Science University of Michigan United States MI United States WIMS ERC United States EECS Department College of Engineering Interdisciplinary Professional Degree Program in Integrated Microsystems Department of Electrical Engin-eering and Computer Science Department of Manufacturing Technology Department of Biomedical Engineering AIMBE United States United States National Academy of Engineering United States Electrical Engineering and Computer Science Chemical and Biomedical Engineering Departments University of Michigan Ann Arbor United States Wireless Integrated Microsystems NSF ERC National Nanotechnology Initiative Network Michigan State University United States Engineering Research Center for Wireless Integrated MicroSystems United States Michigan Technological University United States Michigan Technological University Houghton MI United States Microfabrication Facility Michigan Tech. United States

The Wireless Integrated MicroSystems (WIMS) engineering Research Center (ERC) has developed a broad comprehensive MEMS and microsystem curriculum suitable for upper-level undergraduate students, graduate students, and industry professionals. Five core courses were in the initial curriculum design. The design had flexibility that invited development of other core courses, as well as related technical electives and breadth electives. The core courses provide instruction in MEMS, Microsystems, major design and laboratory measurements, and societal impact. The course enrollments have been strong. A master of engineering in integrated microsystems degree program was developed so that industry professionals would have a focused set of coursework, while providing flexibility that would permit custom tailoring of the total course package to serve specific needs. Distance education dissemination of the courses as whole courses, or as discrete portions of course materials, was intended to be available;that goal has been realized. The core courses originate at the University of Michigan (UM), and have been distributed to Michigan State University (MSU), Michigan Technological University (MTU), Howard University (HU), University of Puerto Rico - Mayaguez (UPRM), and Western Michigan University (WMU). Rochester Institute of Technology (RIT) has used materials from the UM core courses in its offerings. Other institutions that have used the course web-streaming video and course materials are University of Lille, Darmstadt University, and Middle East Technical University. © American Society for engineering Education, 2006.

关键词： Curricula

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Vertically aligned carbon nanotube field emission devices fabricated by furnace thermal chemical vapor deposition at atmospheric pressure

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Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures 2006年第3期24卷 1190-1196页

作者： Wei, S. Kang, W.P. Davidson, J.L. Choi, B.K. Huang, J.H. Interdisciplinary Program in Materials Science Vanderbilt University Nashville TN 37235 Department of Electrical Engineering and Computer Science Vanderbilt University Nashville TN 37235 Department of Materials Science and Engineering National Tsing Hua University Hsinchu 300 Taiwan

Multiwalled carbon nanotubes (CNTs) grown by thermal chemical vapor deposition (CVD) in a tube furnace at atmospheric pressure are reported. The CNTs were synthesized at 750 °C using C2 H2 as the carbon source and a mixture of Ar H2 (80 vol %:20 vol %) as a carrier gas, with N H3 serving as a processing reagent. The catalytic properties of nickel (Ni) particles are strongly affected by the CVD process parameters and this effect is reflected in the morphologies and field emission behaviors of the as-grown CNTs. The flow rate ratio of N H3 to C2 H2 is found to be critical to the formation of vertically aligned CNTs, which demonstrated better field emission characteristics than the randomly oriented nanotubes. The successful synthesis of vertically aligned CNTs at atmospheric pressure in a tube furnace is beneficial for large area mass production such as flat panel field emission displays at lower cost. © 2006 American Vacuum Society.

关键词： Field emission displays

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Total dose radiation response of nitrided and non-nitrided SiO 2/4H-SiC MOS capacitors

Total dose radiation response of nitrided and non-nitrided S...

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作者： Dixit, Sriram K. Dhar, Sarit Rozen, John Wang, Sanwu Schrimpf, Ronald D. Fleetwood, Daniel M. Pantelides, Sokrates T. Williams, John R. Feldman, Leonard C. IEEE Interdisciplinary Materials Science Program Vanderbilt University Nashville TN 37235 United States Department of Physics and Astronomy Vanderbilt University Nashville TN 37235 United States Department of Physics and Engineering Physics University of Tulsa Tulsa OK 74104 United States Department of Electrical Engineering and Computer Science Vanderbilt University Nashville TN 37235 United States Physics Department Auburn University Auburn AL 36849 United States

The total dose radiation response of nitrided and nonnitrided n-type 4H-SiC is reported for metal oxide semiconductor capacitors exposed to 10-keV X-rays under positive bias. The radiation response is affected strongly by differences in the SiC band gap and interface/near interface SiO2 trap density from typical Si MOS devices. Significantly higher net trapped positive charge densities were observed in nitrided n-SiC MOS capacitors compared to the non-nitrided samples. The mechanisms contributing to the differences in the charge trapping in these devices are discussed. Differences in the interfacial layer between SiO2/Si and SiO2/SiC are responsible for the observed dissimilarities in charge trapping behavior. © 2006 IEEE.

关键词： MOS capacitors

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Diamond Ultramicroelectrode Chemical Sensing Arrays

Diamond Ultramicroelectrode Chemical Sensing Arrays

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IEEE SENSORS

作者： W.P. Kang J.L. Davidson K.L. Soh Y.M. Wong D.E. Cliffel A.B. Bonds Department of Electrical and Computer Engineering Vanderbilt University Nashville TN USA Interdisciplinary Program in Materials Science Vanderbilt University Nashville TN USA Department of Chemistry Vanderbilt University Nashville TN USA

Diamond ultramicroelectrode arrays (D-UMEAs) have been fabricated and evaluated experimentally for chemical sensing. D-UMEAs were found to demonstrate higher current density per unit active area than planar diamond macroelectrode and glassy carbon electrode. D-UMEAs could address new operating envelopes in electrochemical detection, and provide stable sensor electrodes for bio and extreme environments.

关键词： Sensor arrays USA Councils Fabrication Microelectrodes Chemical sensors Envelope detectors Chemical and biological sensors Biosensors Biomedical electrodes Powders

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Work Function of Cathode Emitter Materials Obtained by Ab-initio Quantum Mechanical Modeling

Work Function of Cathode Emitter Materials Obtained by Ab-in...

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International Conference on Vacuum Electronics

作者： V. Vlahos E.F. Holby A.K. Berta D.D. Morgan J.H. Booske University of Wisconsin Madison Madison WI USA 1415 Engineering Dr. Madison WI University of Wisconsin Madison USA Interdisciplinary Materials Science Program Madison WI Department of Materials Science and Engineering University of Wisconsin Madison USA Department of Materials Science and Engineering Madison WI Department of Electrical and Computer Engineering University of Wisconsin-Madison Madison WI USA

The work function of a material is a very important figure of merit in determining the material's applicability as an efficient electron emitter. Consequently, the work function of a variety of materials utilized in both thermionic and field-assisted cathodes for electron emission was investigated computationally using ab-initio quantum mechanical modeling methods based on the density functional theory (DFT) approach (Hohenberg and Kohm, 1964). This approach enables the detailed and self-consistent treatment of a system utilizing quantum mechanical principles and yields accurate information pertaining to its electronic properties. Of particular interest are cesium-iodide (CsI) coated carbon-based cathodes (Shiffler et al., 2004), which comprise a very promising class of cold field emitters capable of operating at low global electric fields. However, the exact origin of their enhanced emission properties is not clear, and a better understanding is necessary for further improvement and optimization of this technology. We apply ab-initio quantum mechanical modeling for understanding the origin of the fundamental emission mechanisms of this material system

关键词： Cathodes Quantum mechanics Quantum computing Atomic layer deposition Materials science and technology Thermionic emission Electron emission Density functional theory Convergence of numerical methods Slabs

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An analysis of unlicensed device operation in licensed broadcast service bands

An analysis of unlicensed device operation in licensed broad...

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2005 1st IEEE International Symposium on New Frontiers in Dynamic Spectrum Access Networks, DySPAN 2005

作者： Brown, Timothy X. Interdisciplinary Telecommunication Program Electrical and Computer Engineering Department University of Colorado Boulder CO 80309-0530

ISBN: (纸本)1424400139

Recent FCC proceedings have considered the notion of unlicensed device operation in licensed bands. Licensed users are concerned about harmful interference while unlicensed device manufacturers are concerned that harmful interference is an imprecise design concept. This paper addresses three elements to this debate. First, it advocates for an explicit model of harmful interference to be included in unlicensed device rules. Such a model provides explicit bounded protection to the licensed user while providing assurances and performance goals to the unlicensed device manufacturers. Second, it assesses several proposed methods for unlicensed devices to avoid licensed users and develops variants of each that can achieve the necessary accuracy. Third, it presents an analytic model for assessing harmful interference that not only provides quantitative analysis, but, also provides insight into how factors such as directional antennas, power control, and licensed channel avoidance strategies affect the aggregate interference. Further, it suggests that complex factors such as unlicensed device modulation schemes can be captured in a simple measurement. These ideas are applied to the notice of proposed rulemaking on Unlicensed Operation in the TV Broadcast Bands. © 2005 IEEE.

关键词： Information services

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An analysis of unlicensed device operation in licensed broadcast service bands

An analysis of unlicensed device operation in licensed broad...

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IEEE International Symposium on New Frontiers in Dynamic Spectrum Access Networks, DySPAN

作者： T.X. Brown Interdisciplinary Telecommunication Program Electrical and Computer Engineering Department University of Colorado Boulder CO USA

关键词： Interference TV broadcasting FCC Protection Investments Telecommunication computing Virtual manufacturing Directional antennas Power control Aggregates

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