I am studying the formation process of minerals (i.e., Ca2SO4) on polymer-coated surfaces. For my results, the frequency changes for different overtones are slightly different. In literature, n=3 is typically used. Can I use n=5 or n=7?
From my experience with QCMD, higher overtone numbers are usually subject to more noise. The overtone number refers to which multiple of the fundamental frequency the crystal is vibrating at. For example, if the fundamental frequency is 5 MHz, the 3rd overtone would be 15 MHz, and so on. Each overtone probes a different depth into the material attached to the crystal surface. Because the wave penetrates deeper into the layer at higher overtones, it's possible to gather information about changes that occur deeper in the layer. This can potentially provide more detailed information about the sample. However, these higher overtones are also more sensitive to noise and other perturbations because higher frequency vibrations are more easily affected by factors such as temperature fluctuations, mechanical vibrations, and electrical noise.
Another important consideration is that at higher overtones, the assumptions of the Sauerbrey equation start to break down. The Sauerbrey equation assumes a rigid, homogeneous layer, but at higher overtones, the sensitivity to viscoelastic properties increases, and the layer may not behave as a simple, rigid mass.
Hope my answer will be helpful for you. Here are some references that you can read.
https://www.sciencedirect.com/science/article/abs/pii/S1385894721036640
https://www.biolinscientific.com/blog/why-are-overtones-important-in-qcm
https://www.biolinscientific.com/blog/why-it-is-useful-to-use-multiple-overtones-in-qcm-measurements
- Badges
- Science topic
- Similar topics
- Filing