Adsorption–desorption noise in QCM gas sensors

There are several mechanisms that are related to the fluctuation phenomena in QCM. The aim of our research is to study the sensitivity and the influence of different kinds of noise on sensor resolution. Our experiments are performed on sensors with a sorption layer of polypyrrole which is suitable for detection of water vapor. Based on these experiments, we conclude that 1/f noise caused by quartz internal friction and adoption–desorption (generation–recombination) noise from analyzed gas cause the main components of the measured noise spectral density. The adoption–desorption noise power depends on the physical and chemical parameters of the analyzed gas and it is proportional to the gas density. The adsorption–desorption kinetics is described by Kolmogorovʹs equation and is compared with the Wolkenstein and Langmuir equations.