Carboxylated single-walled carbon nanotubes (SWNTs) based chemicapacitive gas sensors were fabricated by AC dielectrophoretically aligning SWNTs across microfabricated gold electrodes with controlled density/device resistance. Two different sensing configurations (i.e., horizontal/in-plane
and vertical/out-of-plane) were utilized to compare their sensing performance. Upon exposure to water vapor at room temperature, the response (R = [(C – C0/C0] × 100%) increased with an increase in water vapor concentration similar
to that of resistance response. In horizontal configuration, the response was increased with an increase in device resistance which might be attributed to preferentially alignment of semiconducting SWNTs during initial phase of alignment. However, the response was independent of device resistance
in vertical/out-of-plane configuration which indicated that the sensing mechanism is based on the change of dielectric constant of gate and atmosphere.
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