I need to find the the thickness of the films to know the other things.
There is plenty of such approaches, usually based on evolution of interference fringes as mentioned above. Due to particular purposes, lot of variables (e.g. thickness homogeneity, dielectric functions depth-homogeneity) is allowed only as constant values in particular models. Also, required knowledge of thin film and/or substrate properties (e.g. spectral dependencies of dielectric functions) of these models (may) differ.
These techniques are usually based on measurement of transmittance or reflectance (the most general is measurement of both) spectra of thin film in normal direction in UV-Vis-NIR region (let us say 200 – 2500 nm). However, the thicknesses which can be evaluated are limited to range where enough number of suitable interference fringes occurs. Due to this fact, some additional techniques are developed, e.g. angle dependent measurements which increase evaluable thicknesses range and/or decrease necessary range of spectrofotometric data.
Here is a link for some free-access software:
http://www.chalcogenide.org/parav-v2-0-2/
where You can also find links for related papers
http://www.chalcogenide.org/downloads/software/Ganjoo-JOAM-2008.pdf
http://www.chalcogenide.org/downloads/software/Update_Version-2.pdf
where You can find some related references (e.g. well-known R. Swanepoel, J. Phys. E: Sci. Instrum. 16, 1214 (1983). ).
Dear Mr Mallick,
Yes you can do it from the appearance of interference fringes in the transmission spectra. Please find this website (Article): http://www.google.com.my/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=2&cad=rja&ved=0CFgQFjAB&url=http%3A%2F%2Fsemiconductorslab.com%2Fpdfs%2FMatSciPoland%2520(Determination%2520of%2520the%2520thickness%2520and%2520optical%2520constants%2520of%2520transparent%2520indium-doped%2520ZnO%2520thin%2520films%2520by%2520the%2520envelope%2520method).pdf&ei=F6i5UqL1GZS3hAe9v4HQDA&usg=AFQjCNH0Og3lKewbL_9UEr6MxZabY6Z6fQ&sig2=Ivc9bdGy_57akChi7A1EYw&bvm=bv.58187178,d.bGQ
I agree with M. Mahdi. Manifacier`s method is the simplest. One of the main assumptions for this method is that the film is homogeneous (vs depth). If you see a funny shape for the envelop, it could be related to inhomogeneity, or an optical constant dispersion that is not `dielectric-like`.
There is plenty of such approaches, usually based on evolution of interference fringes as mentioned above. Due to particular purposes, lot of variables (e.g. thickness homogeneity, dielectric functions depth-homogeneity) is allowed only as constant values in particular models. Also, required knowledge of thin film and/or substrate properties (e.g. spectral dependencies of dielectric functions) of these models (may) differ.
These techniques are usually based on measurement of transmittance or reflectance (the most general is measurement of both) spectra of thin film in normal direction in UV-Vis-NIR region (let us say 200 – 2500 nm). However, the thicknesses which can be evaluated are limited to range where enough number of suitable interference fringes occurs. Due to this fact, some additional techniques are developed, e.g. angle dependent measurements which increase evaluable thicknesses range and/or decrease necessary range of spectrofotometric data.
Here is a link for some free-access software:
http://www.chalcogenide.org/parav-v2-0-2/
where You can also find links for related papers
http://www.chalcogenide.org/downloads/software/Ganjoo-JOAM-2008.pdf
http://www.chalcogenide.org/downloads/software/Update_Version-2.pdf
where You can find some related references (e.g. well-known R. Swanepoel, J. Phys. E: Sci. Instrum. 16, 1214 (1983). ).
Many thanks for the link to the download of the Materials Science-Poland paper M. Mahdi. I'll add it to my particular collection of a valuable papers.
Also, many thanks for the link Jan Gutwirth. Very useful for working offline and without any spectrophotometer aside you.
What have been suggested by the above all is correct and from the interference fringes we can determine the thickness of the coating. I have used this method is year 2003 in my master's work to determine the thickness of amorphous silicone on glass panel.
One of the easiest methods is the one discussed above (with interference fringes). Very powerful is also (when the thin film is coated on a reflective substrate, e.g. Si-wafer etc.) to use ellipsometry. This gives also (applying an appropriate film model) other film characteristics such as refractive index etc.. Further information can be found here:
http://en.wikipedia.org/wiki/Ellipsometry
or: http://www.jawoollam.com/tutorial_1.html
We use this as a standard method to characterize semi-transparent coatings.
You can also use a contact profilometer (if there is some area of the substrate which is not coated) e.g. Dektak stylus profiler. Also possible: AFM.
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