QCM-D measures the adsorbing mass of molecular layers; spectroscopic ellipsometry measures optical film thickness.
The mass determined by QCM-D contains the masses of both the adsorbed molecules (e. g. proteins) and the embedded water molecules. Since ellipsometry is an optical technique, the water embedded in the film cannot be distinguished from the surrounding water medium. Which means thickness determined by ellipsometry is lower than the thickness determined by QCM-D. When both methods are combined, however, the proportion of embedded water, and thus the thickness of the adsorbed molecule film, can be determined.
Thanks to a successful cooperation between J. A. Woollam Co. and Q-Sense, special mounting adapters have been available for the integration of Q-Sense model E1 into the M-2000 or RC2 ellipsometers from Woollam for many years now. They guarantee predefined measurement conditions like exact positioning, alignment, use of the proper correction effects etc. Mounting is very simple; the same adsorption process can be measured with both methods simultaneously.
Since most adsorption processes do not require the measurement speed of an M2000 or RC2, and – as most liquids absorb in the UV – the visible spectral range is normally sufficient, Woollam now also offers QCM-D adapters for the budget-friendly Alpha-SE. A measurement time of approx. 10 seconds and a simultaneously acquired spectral range of 380 to 900 nm are sufficient. Another advantage is that no compromises need to be made when it comes to measurement sensitivity. The rotating-compensator method ensures a sensitivity in the sub-Ångstrom range.
7th International Conference on Spectroscopic Ellipsometry (ICSE-7)
Berlin, 06 - 10 June 2016
Our team from LOT-QuantumDesign and our partners from J. A. Woollam Co. will be present at the ICSE-7. We look forward to this conference and to many interesting talks and discussions with you.