I would suggest using Attenuated Total Reflectance (ATR) for thin film analysis. For ATR analysis you can use whatever substrate you are depositing on by using a fresh substrate without the thin film as your blank. However, if your film is too thin you may not get any FTIR data since FTIR sensitivity is not as good as other surface sensitive techniques (XPS and ToF-SIMS).
either in transmission with a IR transparent substrate like MgF2, Si, Ge...
or in reflection mode with a IR reflective substrate like Al...
I would suggest using Attenuated Total Reflectance (ATR) for thin film analysis. For ATR analysis you can use whatever substrate you are depositing on by using a fresh substrate without the thin film as your blank. However, if your film is too thin you may not get any FTIR data since FTIR sensitivity is not as good as other surface sensitive techniques (XPS and ToF-SIMS).
ATR-FTIR works well, especially if can deposit directly on the ATR crystal, but David is right sensitivity is quite low. Almost impossible to pick up a clean IR signal of a monolayer from a diamond crystal. I have managed to pick up some characteristic frequencies on silicon sams using a germanium crystal. But if your thin film is a micron thick or bigger you should have little problem.
Thank you all for your answers ..
I'm afraid that my film is too thin less than 100 nm.
If you have access to an ATR I would suggest trying the analysis. I would do multiple scans to increase your signal-to-noise ratio as has been suggested by Soheilmoghaddam.
You can use Silicon substrate. If your sample is a carbon sample, then FTIR will detect,no matter how much thin it is
you can use the ATR IR for such with 64 scan rate..
as measuring is easy in the ATR IR..
what is your base material on which you have deposited 100 nm or less coating ? I am measuring multi bounced ATR spectra of 100 nm or less thick SiOx coating on 60 micrometer thick Polyethylene film. As the penetration depth of IR beam will be around 1 micrometer by this technique I get both Polyethylene and SiOx peaks together. Later we can subtract the spectra of polyethylene so we get information only about SiOx film. Due to low thickness it will show less intensity of the absorbed or transmitted peaks. Feel free to interact if want to discuss anything else at [email protected]
In addition to the options above, which are very good for most sample types, if your film is mechanically stable and self-supporting (e.g. a polymer film), you can measure it in transmission without any substrate. You just suspend it in the beam.
If it is a monomolecular layer, you can measure it with excellent sensitivity by using grazing incidence (GI) reflection on a reflecting (usually metallic) substrate.
Best
Luca
what about using nano-FTIR technique? We were able to measure even monolayer of lipids with this new technique.
Atr-ftir is a good technique for thin films. For more details go through below link.
http://www.sciencedirect.com/science/article/pii/S0032386116301227
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