Thanks, Leandro. No, they don't indicate ATR mode. what the difference between the ATR mode and non mode? How can I analyze the film by FTIR?

Thanks!

It all depends on the FTIR technique used. You can easily see IR fingerprint of monolayers from 1 nm (3-aminopropyl silane) to monolayers of stearic acid (2.0-2.5 nm) depending on packing and therefore tilt angle.

You can do ATR-FTIR, use a single bounce reflectance or diffuse reflectance accessory or IRRAS.

What is film made of and what you want to deposited on?

It may be a confusion between the actual film thickness and IR penetration depth that is about 0.7 microns or 700 nm. Can be 0.5 - 2 microns depending on substrate. This is commonly used and known in ATR-FTIR.

dp= depth of penetration of the IR beam into the sample, defined as the distance required for the electric field amplitude to fall to e^-1 of its value at the surface;

λ= wavelength of light

θ = the angle of incidence of the IR beam relative to a perpendicular from the surface of the crystal.

Look for additional details in the literature on ATR-FTIR

Many thanks to Jhony.

Yes, the penetration depth for ATR model measurement is about 700nm.

It is a SiOx film or a organosilicone film on a silicon wafer.

if I want to measure a film with 200nm, which FTIR model should be used?

ATR-FTIR is the easiest.

Use the base silicon wafer as background.

For sample acquisition use the modified silicon wafer.

When you get the spectrum, check for the C-H sym and asym stretching bands betwee 2800-3000 wavenumbers (no need to worry about the bending modes or C-C bands in the fingerprint region).

Also you should obtain the Si-O bands also very intense.

If you see the C-H stretching, is sufficient to know that your wafer is modified.

If you want to measure film thickness, I suggest ellipsometry or AFM.

Hope this helps...

Thank you so much, Jhony.

I will try to get the IR spectrum of a 200nm film by ATR-FTIR according to your suggestion.

I suggest you use the NDE technique known as XRR (X-ray Reflectivity) to cross check your FTIR results unequivocally :-)

I believe ATR would work for your 200 nm film. ATR has been used to study the surface chemistry during atomic layer deposition process which require a detection in the Angstrom level. 

http://pubs.acs.org/doi/abs/10.1021/jp8028616

I suggest to try in transmittance mode because I think that wafer silicon are transparent in middle IR . First the background with silicon wafer and then the silicon wafer +the coating .