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Sources électroniques à base de nanotubes de carbone - Application aux tubes amplificateurs hyperfréquence.

Abstract : Understanding the properties of matter at the atomic scale, results considerable progress in science and technology in the late 20th century, is one of progress that has led to the development of what is now called nanoscience. Richard P. Feynman, Nobel Prize for Physics in 1965 for his work on electrodynamics Quantum had prophesied in the 19,591 range of possibilities opened up by the manipulation of material atom by atom. The laws of physics no longer apply to macroscopic this scale and become purely quantum behavior. You can change the properties of matter thus paving the way for futuristic applications. Nanotechnology - concepts and methods for nanoscience applications - have vast fields of applications in microelectronics and materials by example. And the opportunities are increasing for these specific areas but also in biotechnology, photonics and information technology suggestive of social and economic benefits énormes2. Yet it has long used nanomaterials (glass, ceramics, ...) and chemists rely on molecules of different sizes. Can we then consider this science as news? In fact, what has changed is the opportunity, through the development new tools, make, observe, analyze, assemble, understand nano-objects which are the building blocks of nanotechnology. In this manuscript, we will consider the particular case of new molecules: carbon nanotubes are studied for their remarkable properties. Their qualities electron transport are candidates for the realization of transistors, diodes or more RAM. Their mechanical properties and low weight make it any component of composite materials. Finally, their high aspect ratios due to micrometer lengths and radii are nanoscale electron sources very interesting field emission that can be used in flat screens for microscopy. This latter application of carbon nanotubes as electron source in the void that is the cause of all this work and is the subject of this brief. When the transistor was invented by Bardeen, Brattain and Shockley in the years 19,503 and the first integrated circuits were introduced in 19604 years, it seemed that the time of the electronic vacuum was counted. The emission in the vacuum thermionic effect indeed requires heating a cathode to about 1000 ° C to make electrons. Yet in 1961, the Stanford Research Shoulders Institute (SRI) has the idea of a new device, micrometer-sized, based on the tunnel effect, as a new électrons5 source. And what are the manufacturing technologies from the microelectronics which will enable the manufacture of these new electron sources say cold (because operating at room temperature) based on this principle purely quantum. Thus, when in 1968, Spindt, Shoulders hired by the IRS, published his first Results on the production of spikes in pyramidal molybdène6, it triggers an interest for electronic transmitters and a rebound in electronics in vacuum with target applications such as flat panel displays, high frequency devices, ... So the early years of the scientific community will be almost exclusively dedicated to improving this specific type of issuer. One of the finest achievements being demonstration of operation in 1993 a flat screen 6 "based on this technologie7. From 1994, however, this community will gradually turn towards new materials more robust and also easier and cheaper to produce. This is In 1995 and Rinzler8 Heer9 will demonstrate the electron emission from nanotubes carbon, a new form of carbon discovered in 1991 by Iijima10. Properties geometric, electrical, mechanical, chemical properties of these objects are indeed a material remarkable for the field emission. They are also extremely robust and processes growth used to manufacture low-cost (over large areas) cathode very performance. In addition, one of the big disadvantages of Spindt tips for use at high frequencies is the proximity between the tip and the extraction grid (~ 1μm) which is imposed by the manufacturing process and leads to higher capacity thereby limiting the frequency use. With carbon nanotubes, this issue was raised with the possibility to exclude the grid at greater distances (~ 100μm) and cutoff frequencies and more high. With amplification factors much larger than the spikes pyramidal it also maintains a flight with reasonable voltages. The study of field emission properties of carbon nanotubes will be and the bulk of this manuscript in which we will also try to show the benefits of these sources compared to other materials. The goal here is the use of these sources in microwave tube amplifiers. The basic idea that led to this study is as follows: the thermionic cathodes Conventional satisfactory and are still under development. There has currently no reason to replace the tubes. However one perceives the need a new technology for high frequencies (> 30GHz). The dream of the designers electronic tubes and is replaced by the hot cathode cold cathode which integration should allow one hand to reduce the size and weight of at least a factor of 2 and above all to significantly improve performance, particularly at high frequencies. The cutoff points such as "Spindt" being too weak to address this frequency zone (a demonstration of 199,711 in 10GHz modulation is still Today the state of the art on these devices), carbon nanotubes provide a technology interesting and challenging to replace the hot cathode. But for that must develop a source that can issue a certain density currents with certain life. This has been the object of this work: designing, developing, understand, optimize a field emission source based on carbon nanotubes. The first part will introduce the world of tubes and microwave sources electronics. We try to understand the limits of current technology and the interest presented by these new sources of carbon nanotubes. The second part will focus on the material. Firstly through its exceptional Properties and methods of manufacture. A state of the art of its use as a source electronics allow us to understand the direction we have chosen to make powerful sources. We present the main experimental achievements. The third part will be devoted to field emission in nanotubes individual carbon. In presenting specific tool that was used for these measures and main results that allowed us to understand and improve the performance. The fourth part will be when it dedicated to the field emission measurements on networks of nanotubes. We present the main results. These will coupled with individual results to show that it is possible to predict the behavior a cathode. The fifth part will demonstrate the modulation of an electron beam Microwave from a carbon nanotube cathode. First results obtained in a diode at 1.5GHz. Then those obtained in a triode 30GHz. We will end with all these results, what they bring to the understanding This new type of sources and perspectives they open when the use of cellesci in commercial devices.
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  • HAL Id : pastel-00001904, version 1



Eric Minoux. Sources électroniques à base de nanotubes de carbone - Application aux tubes amplificateurs hyperfréquence.. Physique [physics]. Ecole Polytechnique X, 2006. Français. ⟨pastel-00001904⟩



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