{"id":1861,"date":"2010-07-13T14:11:18","date_gmt":"2010-07-13T18:11:18","guid":{"rendered":"https:\/\/wpmu2.mit.local\/?p=1861"},"modified":"2010-08-04T10:00:35","modified_gmt":"2010-08-04T14:00:35","slug":"electron-impact-ionization-pump-using-double-gated-isolated-vertically-aligned-carbon-nanotube-arrays","status":"publish","type":"post","link":"https:\/\/wpmu2.mit.local\/electron-impact-ionization-pump-using-double-gated-isolated-vertically-aligned-carbon-nanotube-arrays\/","title":{"rendered":"Electron-impact-ionization Pump using Double-gated Isolated Vertically Aligned Carbon Nanotube Arrays"},"content":{"rendered":"
\"Figure<\/a>

Figure 1: Electron-impact-ionization pump structure consists of a field-emission source (CNTs, an extractor gate and a focus gate), an electron-impact-ionization region (length of L) and an ion-implantation getter.<\/p><\/div>\n

There is a need for microscale vacuum pumps that can be readily integrated with other MEMS and electronic components at the chip-scale level. Vacuum pumps exhibit favorable scaling and are promising for a variety of applications such as low-power portable mass spectrometers and sub-mm wavelength vacuum amplifiers. This project aims to develop the technology for a micro-fabricated electron-impact-ionizer pump.\u00a0 The micropump consists of a field-emission electron source that is an array of double-gated isolated vertically aligned carbon nanotubes (VA-CNTs), an electron-impact-ionization region, and an ion implantation getter, as shown in Figure 1. The pump works as follows: first, electrons are field-emitted from the VA-CNT array; then, the electrons are accelerated at a bias voltage that maximizes the probability of collision with neutral gas molecules, this way achieving ionization by fragmentation of the molecules; finally, ions are implanted into the getter.<\/p>\n

\n

\"Figure<\/a><\/p>\n

Figure 2: The solution of the electric field for an emitter of 20 nm tip radius, 1\u00a0\u00b5m height, and 0.24 \u00b5m gate aperture. A field factor (\u03b2G<\/sub>) of 2.1×105<\/sup> V\/cm is obtained.<\/p>\n<\/div>\n

In a double-gated field-emitter array, the first gate (extractor) is used to extract electrons out of the tip, while the second gate (focus) is biased at a lower voltage than the first gate or emitter to focus the emitted electrons and collect the back-streaming ions, thus protecting the tip [1<\/a>]<\/sup>. In this work, we are designing and simulating double-gated isolated VA-CNT field-emission arrays to study how the field-emitter tip position relative to the two gates affects the device performance. To quantify the effectiveness of the gates to affect the total emission current, the gate field factor (\u03b2G<\/sub>) and the focus field factor (\u03b2F<\/sub>) are examined using the commercial simulation software COMSOL. Figure 2 shows a solution of electric field for an emitter with 20 nm tip radius and 1 mm height with 0.24 mm aperture from a single gate. From this simulation, we obtain a gate field factor of 2.1×105<\/sup>V\/cm.<\/p>\n

\r\nReferences
  1. L.-Y. Chen, L. F. Velasquez-Garcia, X. Wang, K. Cheung, K. Teo, and A. I. Akinwande, \u201cDesign, Fabrication and Characterization of Double-Gated Vertically Aligned Carbon Nanofiber Field Emitter Arrays.\u201d in Vacuum Nanoelectronics Conference, <\/em>2007, pp 82-83. [↩<\/a>]<\/li><\/ol><\/div>","protected":false},"excerpt":{"rendered":"

    There is a need for microscale vacuum pumps that can be readily integrated with other MEMS and electronic components at…<\/p>\n<\/div>","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[11],"tags":[4115,71,4204],"_links":{"self":[{"href":"https:\/\/wpmu2.mit.local\/wp-json\/wp\/v2\/posts\/1861"}],"collection":[{"href":"https:\/\/wpmu2.mit.local\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wpmu2.mit.local\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wpmu2.mit.local\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/wpmu2.mit.local\/wp-json\/wp\/v2\/comments?post=1861"}],"version-history":[{"count":7,"href":"https:\/\/wpmu2.mit.local\/wp-json\/wp\/v2\/posts\/1861\/revisions"}],"predecessor-version":[{"id":2317,"href":"https:\/\/wpmu2.mit.local\/wp-json\/wp\/v2\/posts\/1861\/revisions\/2317"}],"wp:attachment":[{"href":"https:\/\/wpmu2.mit.local\/wp-json\/wp\/v2\/media?parent=1861"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpmu2.mit.local\/wp-json\/wp\/v2\/categories?post=1861"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpmu2.mit.local\/wp-json\/wp\/v2\/tags?post=1861"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}