Effect of humidity on the properties of NO2 sensors based on thin WO3 and SnO2 films modified with gold

摘要

The effect of humidity on the electrical and gas-sensitivity properties of NO2 sensors based on thin (100 nm) nanocrystalline films of tungsten trioxide and tin dioxide with additions of gold in the bulk and on the surface (Au/WO3:Au, Au/SnO2:Sb,Au) is investigated. It is found that the conductivity of these films in pure air increases only slightly as absolute humidity A rises from 2 to 16 g/m(3), the responses for nitrogen dioxide in the concentration range of 0.45-10 ppm do not depend on humidity, and the response time is shortened as A rises. Analysis of experimental data using a model based on the assumed microcrystal availability in WO3 and SnO2 thin films connected by conductivity bridges shows that the values of the heat of adsorption Delta E (N) and activation energies of adsorption E (aN) and desorption E (dN) of ions NO (2) (-) on the films surface modified gold, do not depend on the humidity.