The diffusion behavior of mercury into both gold and silver electrodes of polished and roughened quartz-crystal microbalances was presented. Several quartz-crystal microbalances devices were exposed to mercury vapour for 8h and allowed to desorb for 5h under controlled nitrogen atmosphere. The process was repeated for different Hg concentrations of 1.02, 1.87 and 3.65mg/m3 at an elevated temperature of 40C. The chemical composition and surface morphology of each secondary ion mass spectroscopy surface was characterized by inductively coupled plasma mass spectroscopy, secondary ion mass spectroscopy, atomic force microscope and field emission secondary electron microscope. The Ag electrodes were found to contain up to 16% more adsorbed/amalgamated Hg by mass than the Au samples. It was found that the ratio of amalgamated to adsorbed Hg was less for Au than Ag. Secondary ion mass spectroscopy analysis confirmed high Hg diffusion through rough substrates, 40 days after Hg exposure. In situ sticking probability of the tested mercury vapour concentrations to Au and Ag surfaces at 40C was found to drop at quicker rates than the reported Hg–Au and Hg–Ag room temperature values. Overall, in the context of Hg vapour phase gas sensing applications, the rougher gold substrate was found to outperform the other samples due to its superior adsorption/desorption properties.

Mercury Diffusion in Gold and Silver Thin Film Electrodes on Quartz Crystal Microbalance Sensors. Y.M.Sabri, S.J.Ippolito, J.Tardio, A.J.Atanacio, D.K.Sood, S.K.Bhargava: Sensors and Actuators B, 2009, 137[1], 246-52