  Nanocrystalline CuO-CuFe2O4 composite thin films were developed from CuFeO2
ceramic target using a radio frequency sputtering method followed by a thermal
oxidation process. This fabrication process helps to develop porous sensing
layers which are highly desirable for solid state resistive gas sensors. Their
sensing properties towards ethanol and hydrogen gas in dry air were examined at
the operating temperatures ranging from 250 deg C to 500 deg C. The electrical
transients during adsorption and desorption of the test gases were fitted with
the Langmuir single site gas adsorption model. A composite thin film with a
total thickness of 25 nm showed highest response (79%) towards hydrogen (500
ppm) at the operating temperature of 400 deg C. The shortest response time
(tres) was found to be ~60 and ~90 seconds for hydrogen and ethanol
respectively. The dependence of the response of the sensor on gas concentration
(10-500 ppm) was also studied.
