Conduction invasion noise in nanoparticle WO3/Au thin-film devices for gas sensing application

Conduction noise measurements were carried out in the 0.3-45 Hz frequency range on Au films covered by a thin layer of tungsten trioxide (WO3) nanoparticles. Exposing the films to alcohol vapor resulted in a gradually increased noise intensity which went through a maximum after an exposure time of the order of 15 min. The maximum noise intensity could increase by several orders of magnitude above the initial level. Longer exposure times made the noise decrease and approach its original value. This effect was not observed in the absence Of WO3 nanoparticles. The phenomenon is discussed in terms of a new 'invasion noise' model in which the noise is related to the insertion and extraction of mobile chemical species.