科研之友
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摘要
MOSFET gas sensors with ITO semimetal gates of different lengths but constant width have been fabricated and presented for hydrogen and carbon monoxide detection under different gas concentrations up to 1000 ppm. Hydrogen and carbon monoxide determinations were achieved by monitoring the change in drain currents of the transistors operated at various temperatures. We have found that the ITO-MOSFET sensor operated in day light showed a "normally on" behavior. To eliminate any current changes under light illumination in the laboratory, we report the results obtained in dark condition. ITO-MOSFET sensor with gate length of 50 micrometer operated at 135 degrees C showed response value of 23 mu A towards 1000 ppm hydrogen gas at a gate voltage of 5 V with a drain source voltage of 20 V. However, when the ITO-MOSFET sensor has been tested towards carbon monoxide this showed a strong decrease from 23 to 4.0 mu A. This is a clear demonstration that the ITO-MOSFET sensor has an enhanced selectivity on hydrogen gas as revealed by much higher response value towards hydrogen than carbon monoxide. When we measured the ITO-MOSFET sensor with a larger gate length of 200 micrometer towards hydrogen, we found a decrease in sensing response from 23 to 11.5 mu A measured under similar conditions as for the sample with the gate length of 50 micrometer. The sensor response time with t(90) of 20 s and recovery time of 1 min have been found quite fast for the ITO-MOSFET with gate length of 50 micrometer towards hydrogen gas.
- 出版日期2011-5
