Influence of the surface roughness on the sorption sensitivity of quartz resonators

The aim of the investigation is to improve resonator s sensitivity by increasing the surface of sorption. The sensitivity of quartz resonator SnO₂ structure for registration of ammonium concentration in vapour phase is studied. The different effective surface of a quartz resonator wafers with thin SnQ deposited on it are used for determining its influence on the sorption ability. For this purpose, quartz substrates with different roughness have been prepared using abrasive materials with different size of the grain from 1 m to 14 m. In this way the average effective area of the electrodes has been changed. The surface s roughness of the quartz substrate and those of the SnO₂ layers on it were estimated by using scanning electron microscopy (SEM). The quality comparison among different surfaces of quartz substrate roughness and SnO as a result of use of various abrasive is carried out. The investigated structures have been formed on quartz substrates with different roughness on which consequently were deposited Au electrodes by vacuum thermal evaporation with a thickness of 120 nm. The thin 90 nm SnO were prepared by RF magnetron sputtering. The influence of the effective surface of quartz resonator with thin SnCh on it of sorption ability has been studied. So created structures were used for NH₃ monitoring in a range concentration from 10 ppm to 5000 ppm. Correlation has been established between sorption ability of SnO layers as a function of the effective electrode surface. Observed dependence could be used for improving the sensitivity of resonator - SnO structures used for NH₃ registration and preparing of NH₃ sensor elements.