Application specific electrode-integrated nanotube cathodes (ASINCs) for miniature analytical instruments for space exploration

Manohara, Harish; Bronikowski, Michael J.; Toda, Risaku; Urgiles, E.; Lin, Robert; Yee, Karl; Kaul, Anupama B.; Hong, John

doi:10.1117/12.777322

Cited by 4 publications

(7 citation statements)

References 13 publications

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“…Moreover, the ionization efficiency of our devices is almost four times larger than the ionization efficiency reported by Chen et al using arrays of double-gated isolated PECVD CNTs, with argon at 5.6 mtorr [48]. In addition, our devices have an estimated field factor from the FN plot that is 50% larger than the corresponding values reported by Manohara et al [39], which implies that our ionizer can extract more current and, hence, produce more ion current with less bias voltage. We speculate that the smaller field factor in the work of Manohara et al is related to the shadowing effect that their CNTs suffer due to their proximity within the same fiber.…”

Section: Discussioncontrasting

confidence: 72%

“…Yoon et al reported a MEMS ionizer that uses a tungsten filament [33], a nickel filament [34], or carbon nanotubes (CNTs) [34] as electron source, although no ionization data were provided. Other researchers have developed CNT-based EIIs suitable for portable MS, including Hwang et al [35], Bower et al [36], Chen et al [37], Park et al [38], and Manohara et al [39]. In addition, low-power, portable, and high-pressure operation compatible glow-discharge ionizers have been developed.…”

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confidence: 99%

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CNT-Based MEMS/NEMS Gas Ionizers for Portable Mass Spectrometry Applications

Velásquez–García

Gassend

Akinwande

2010

J. Microelectromech. Syst.

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We report the fabrication and experimental characterization of a carbon nanotube (CNT)-based MEMS/NEMS electron impact gas ionizer with an integrated extractor gate for portable mass spectrometry. The ionizer achieves low-voltage ionization using sparse forests of plasma-enhanced chemical-vapordeposited CNTs as field emitters and a proximal extractor grid with apertures aligned to the CNT forests to facilitate electron transmission. The extractor gate is integrated to the ionizer using a high-voltage MEMS packaging technology based on Si springs defined by deep reactive ion etching. The ionizer also includes a high-aspect-ratio silicon structure (μfoam) that facilitates sparse CNT growth and also enables uniform current emission. The devices were tested as field emitters in high vacuum (10 −8 torr) and as electron impact ionizers using argon at pressures of up to 21 mtorr. The experimental data show that the MEMS extractor gate transmits up to 66% of the emitted current and that the ionizers are able to produce up to 0.139 mA of ion current with up to 19% ionization efficiency while consuming 0.39 W. [2009-0246] Index Terms-Carbon nanotubes (CNTs), deep reactive ion etching (DRIE), electron impact ionization, field emission, gas ionizer, portable mass spectrometry (MS), 3-D MEMS packaging. I. INTRODUCTION M ASS SPECTROMETERS are powerful analytical tools that are helpful to quantitatively determine the chemical composition of a sample. Unfortunately, conventional mass spectrometry (MS) hardware is bulky and power hungry, which limits the range of applications that the technology can satisfy. The development of gas chromatography and MS (GC/MS) systems that are small, light, mechanically and thermally robust, and low-powered would enable their portability and therefore would expand the applicability of MS techniques. Portable GC/MS systems, either as individual units or as part of massive networks, can be used in a wide range of in situ applications including geological survey, law enforcement, environ-Manuscript

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Section: Discussioncontrasting

confidence: 72%

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confidence: 99%

CNT-Based MEMS/NEMS Gas Ionizers for Portable Mass Spectrometry Applications

Velásquez–García

Gassend

Akinwande

2010

J. Microelectromech. Syst.

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“…However, our ionizer should have higher ionization efficiency if operated at higher pressures. In addition, our ionizer has an estimated field factor in the linear part of the FN plot that is 50% larger than the corresponding values reported by Manohara et al [19], which should be related to the shadowing effect that their CNTs suffer due to their proximity within the same fiber.…”

Section: Experimental Characterizationmentioning

confidence: 79%

CNT-based gas ionizers with integrated MEMS gate for portable mass spectrometry applications

Velásquez–García

Gassend

Akinwande

2009

TRANSDUCERS 2009 - 2009 International Solid-State Sensors, Actuators and Microsystems Conference

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We report the fabrication and experimental characterization of a novel low-cost carbon nanotube (CNT)-based electron impact ionizer (EII) with integrated gate for portable mass spectrometry applications. The device achieves low-voltage ionization using sparse forests of plasma-enhanced chemical vapor deposited (PECVD) CNTs field emitter tips, and a proximal gate with open apertures to facilitate electron transmission. The gate is integrated using a deep reactive ion etched (DRIE) springbased high-voltage MEMS packaging technology. The device also includes a high aspect-ratio silicon structure (µfoam) that facilitates sparse CNT growth and limits the electron current per emitter. The devices were tested as field emitters in high vacuum (10 -8 Torr). Electron emission starts at a gate voltage of 110 V, and reaches a current of 9 uA at 250 V (2.25 mW) with more than 55% of the electrons transmitted through the gate apertures. The devices were also tested as electron impact ionizers using Argon. The experimental data demonstrates that the CNT-EIIs can operate at mtorr-level pressures while delivering 60 nA of ion current at 250 V with about 1% ionization efficiency. KEYWORDSCarbon nanotubes (CNTs), DRIE, gas ionizer, electron impact ionization, field emission, portable mass spectrometry, 3D MEMS packaging.

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“…After initially achieving> 2 A1cm 2 at 4 V/Jlm, we have optimized the CNT growth process and the architecture in recent times to routinely produce 10 to 25 A1cm 2 at applied fields of5 to 10 V/Jlm [7]. These tests were conducted using CNT bundle array samples that occupied a circular area of 100 Jlm diameter (see Figure 2(a)), which is considered a large area source for our applications.…”

Section: Application Specific Electrode-integrated Nanotube Cathodes mentioning

confidence: 99%