A MEMS-Based Ionization Gas Sensor Using Carbon Nanotubes

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We demonstrate here the successful operation of an ionization gas sensor with a gap spacing <formula formulatype="inline"><tex>$S$</tex></formula> of 2 or <formula formulatype="inline"><tex>$\hbox{7}\pm \hbox{0.4}\ \mu\hbox{m}$</tex></formula> and using carbon nanotubes as the electrode material. The device is chip based and fabricated using a microelectromechanical system process. Application of a bias of 0.6–1.8 V <formula formulatype="inline"><tex>$(S\approx\hbox{2}\ \mu\hbox{m})$</tex></formula> or 12–15 V <formula formulatype="inline"><tex>$(S\approx\hbox{7}\ \mu\hbox{m})$</tex></formula> to the electrodes generates an electric field that is sufficient to field ionize He, <formula formulatype="inline"><tex>$\hbox{CO}_{2}$</tex> </formula>, and their mixtures in air with high sensitivity and selectivity. The approach is considered as effective for lowering the operation voltage of ionization gas sensors below 36 V (safety voltage criterion) and is significant for the development of the smart device in this field. </para>