Miniaturized electron-impact-ionization pumps using double-gated isolated vertically aligned carbon nanotube arrays
Name
818652051-MIT.pdf
Description
Full printable version
Size
9.2 MB
Format
Adobe PDF
Checksum (MD5)
31d67efcc8265896532eb7a93a7c3fad
Author(s)
Jayanty, Vivi
Advisor(s)
Luis Fernando Velásquez-García.
Date Issued
2012
Publisher
Massachusetts Institute of Technology
Abstract
There is a need for microscale vacuum pumps that can be readily integrated with other MEMS and electronic components at the chip-scale level. Miniaturized ion pumps exhibit favorable scaling down because they are surface-limited and miniaturization increases the ratio between the active surface and the chamber volume, resulting in enhanced ionization and pump rates. Therefore, scaled-down ion pumps are a promising choice for a variety of applications including portable mass spectrometers and sub-mm wavelength vacuum amplifiers. Our micropump architecture consist of a field-emission electron source that is an array of double-gated isolated vertically aligned carbon nanotubes (VA-CNTs), an electronimpact- ionization region, and a non-evaporative ion-implantation getter. Single-gated VA-CNT FEAs were tested as field emitters in high vacuum (10-9 Torr). The current density of the tested device is ~0.5A/cm2 (total current of 0.4mA) and a field enhancement factor of 1.41 x106 V/cm was measured, which is comparable to the simulation results by COMSOL. Two ways to fabricate double-gated VA-CNT FEAs were reported: one has the focus gate in plane with the extractor gate and the other has the focus gate above the extractor gate. Due to problems on fabrication process of double-gated VA-CNTs (short circuit between emitters, extractor gate, and focus gate), we were not able to collect four-terminal measurement, electron-impact-ionization, and pump data. However, procedure on how to collect and analyze field emission data with two gates to find [beta]G and [beta]F was described. In addition, procedures on how to collect and analyze data on electron impact ionization pump were also presented.
Description
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 67-71).
Subjects
Electrical Engineering and Computer Science.
MIT Department
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
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