Surveying the market of QCM:s, one will come across a vast range of different QCM versions. Extended versions such as the QCM-A, QCM-D, QCM-I, and QCM-R are but a few examples, and they all seem to provide similar information. So, what are the differences between the various versions, and does it matter which one you use?
Different QCMs are suitable for different applications
The Sauerbrey equation, which is the relation that gave birth to the QCM technology, assumes that the layers to be characterized are thin and rigid. When the thickness of the film increases, the material properties of the film will start to matter and influence the accuracy of the mass determined by the Sauerbrey equation. This means that if you intend to study anything else than rigid films in a vacuum, then you need a QCM with additional capabilities in terms of information collection, to compensate for the complexity of the layer.
Recover the quantification capabilities by measuring the energy losses
To evaluate soft and/or thick films, both the frequency and damping of multiple harmonics are needed. Although the technology names out there suggest that there is an immense number of ways to measure the energy loss, there are essentially only three ways to do so, via 1) impedance spectroscopy, via 2) the decay time of the oscillation or via 3) the resistance. The respective QCM abbreviations, however, often give little information on the actual measurement principle, and what information and data quality that the respective technology offers
Which QCM should you choose?
So, which of all the available QCM setups should you go for? The answer to this question depends on your intended use of the instrument. Will you measure in gas phase or in liquid? Will you study viscoelastic layers? Will the processes that you are studying be fast or slow? And will you have the need for quantitative information, or will qualitative information be sufficient?
Download the whitepaper to learn more about the differences between the various QCM options, the pros and cons of the different ways of measuring and when and why to select which method.
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