Investigating the Mass Sensitivity of Quartz Crystal Microbalances with Circularly Symmetric Electrodes in the Third Overtone Mode.

This study investigates the mass sensitivity of a quartz crystal microbalance (QCM) with a circular symmetric electrode (M-M type) operating in the third overtone mode and finds that its central mass sensitivity is nearly five times greater than that of the fundamental mode, as determined through a deposition experiment, rather than the three times greater central mass sensitivity predicted by classical theory. The reasons for this phenomenon were determined through a combination of theoretical calculation and finite element simulation. The results revealed that (1) compared with the fundamental mode, the third overtone mode exhibits a more pronounced energy trapping effect, leading to a sharper mass sensitivity distribution and a more concentrated sensitivity in the central region and (2) the third overtone resonance frequency is slightly higher than three times the fundamental resonance frequency.