Abstract
Miniaturized gas sensors or electronic noses to rapidly detect and differentiate trace amount of chemical agents are extremely attractive. In this paper, we report on the fabrication and characterization of a functional tin oxide nanoparticle gas sensor. Tin oxide nanoparticles are first synthesized using a convenient and low-cost mini-arc plasma source. The nanoparticle size distribution is measured online using a scanning electrical mobility spectrometer (SEMS). The product nanoparticles are analyzed ex-situ by high resolution transmission electron microscopy (HRTEM) for morphology and defects, energy dispersive X-ray (EDX) spectroscopy for elemental composition, electron diffraction for crystal structure, and X-ray photoelectron spectroscopy (XPS) for surface composition. Nonagglomerated rutile tin oxide (SnO2) nanoparticles as small as a few nm have been produced. Larger particles bear a core-shell structure with a metallic core and an oxide shell. The nanoparticles are then assembled onto an e-beam lithographically patterned interdigitated electrode using electrostatic force to fabricate the gas sensor. The nanoparticle sensor exhibits a fast response and a good sensitivity when exposed to 100 ppm ethanol vapor in air.
Highlights
Rutile tin oxide (SnO2), a wide band gap (3.6 eV at 300 K [1]) n-type semiconductor material, is widely used as sensing elements in gas sensors [2]
Recent studies [5, 6] have shown that the use of tin oxide nanocrystals as sensing elements significantly improves the response and the sensitivity of sensors since the space charge region may develop in the whole crystallite
The higher processing temperature employed in aerosol synthesis facilitates production of stable phases that are difficult to achieve in colloidal synthesis [12]
Summary
Rutile tin oxide (SnO2), a wide band gap (3.6 eV at 300 K [1]) n-type semiconductor material, is widely used as sensing elements in gas sensors [2]. Recent studies [5, 6] have shown that the use of tin oxide nanocrystals as sensing elements significantly improves the response and the sensitivity of sensors since the space charge region may develop in the whole crystallite. Tin oxide nanoparticles have been produced by both colloidal and aerosol routes. Nanoparticles produced in the gas phase can be subsequently deposited onto solid substrates for immediate device applications. Aerosol routes provide more flexibility in process control [10, 11] and improve the compatibility of the nanoparticle sensor fabrication process with existing microelectronics fabrication facilities. The new source shows great potential in producing high-quality tin oxide nanoparticles for gas sensing applications. The microfabricated nanoparticle sensor exhibits good sensitivity and dynamic response to low concentration ethanol gas
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