Chemical sensing with ZnO nanowire field-effect transistor

Zinc oxide nanowires are configured as n-channel FETs. These transistors are implemented as chemical sensors for detection of various chemical gases. It is observed that the nanowire conductance is reduced when it is exposed to oxygen, nitrogen dioxide, ammonia gases at room temperature. Its ammonia sensing behavior is observed to switch from oxidizing to reducing when temperature is increased to 500 K. This effect is mainly attributed to the temperature dependent Fermi level shift. In addition, carbon monoxide is found to increase the nanowire conductance in the presence of oxygen. Furthermore, the detection sensitivity dependence on the nanowire radius is presented.