GAS-SENSING USING A CHARGE-FLOW TRANSISTOR

We report on the successful fabrication of an array of charge-flow transistors incorporating polyaniline films. The electrical d.c. characteristics have been found to be similar to those of conventional metal-oxide-semiconductor field-effect transistors. However, on application of a gate voltage, V-gs greater than the threshold voltage, a delay is observed in the response of the drain current. This is attributable to the time taken for the resistive polyaniline layer to charge up to V-gs. These delay characteristics have been found to be dependent upon the ambient, suggesting that the charge-flow transistor device can be used as an effective gas sensor. Results are presented of studies using NOx and SO2, showing that the device can detect reversibly gas concentrations down to 1 ppm.