A field effect transistor (FET) sensor for NO2 was fabricated by depositing
an NaNO2 layer together with an Au electrode over the gate area. The NaNO2
-attached FET exhibited almost ideal FET behavior at 180 degreesC in air. T
he threshold voltage was found to shift up ward in a well controlled manner
with increasing NO2 concentration of the atmosphere. Under the condition o
f a fixed source-drain voltage (3.0 V), the gate-source voltage (V-GS) nece
ssary to keep the drain current at a small constant value (200 muA) was fou
nd to increase linearly with an increase in the logarithm of NO2 concentrat
ion in the range from 500 ppb to 10 ppm. The times of 90% response and reco
very to switching on and -off 500 ppb NO2 were about 2 and 4 min, respectiv
ely. The NO2 sensitivity was hardly or only slightly affected by variations
in the concentrations of coexistent O-2, CO2 Or H2O. (C) 2001 Elsevier Sci
ence B.V. All rights reserved.