We have a film of eosin yellow dye on glass substrate. We have tried building genosc model using Lorenz and GLAD. Also tried those of other polymers. But we are not able to fit the ellipsometry data. Any suggestions please.
What wavelength range do you use and is it transparent in a region of spectral window provided by your ellipsometer ? If it is some where transparent, you can start off with Cauchy and then proceed to absorbing regions with the use of oscillators. You can do a wavelength by wavelength fit for that. Also, since you are doing your measurements on glass susbtrates, you will have to take into account back surface reflections either through the software or though an index matching tape which you can stick on the back side of the substrate. Also, if the film is not homogeneous in thickness, it can cause depolarization which will further complcate the situation. You should also do measurement at different angles of incidence to see if you get a difference in pseudo optical constants, if yes, then you will extract more information from your sample. If they are same, then one angle is sufficient for the measurement. If you are using WVASE software (J.A.Wollam Co.) then you can send me the data and I can look into it.
Thank You so much sir. The wavelength range is 240-1000nm. I have tried with the cauchy model and precaution is taken to avoid multiple back reflections. Only thing is that i am not able to fit the data very well even with built genosc.
Since you use WVASE software, you can send me the raw data and I can give it a try.
Can you give some approx. thickness of the layer and how do you form this layer on the substrate ?
Thickness is approximately 300nm. I think we need to extend the measurement range to NIR. Its absorbance peak is near 550nm.
I have just built a rough model in the range of 700-1000 nm and it gives thickness of approx 92 nm. There are correlations among parameters but the data is noisy for delta as compared to psi. Try to increase the number of revolutions per measurement and see if that helps in reducing noise. Also if you can deposit this film on a silicon wafer, then that may help as the underlying structure of Si will help in modelling as compared to a glass substrate. I have also attached the fit test for the thickness just for your reference. Link is for the env file for the model.
http://dropcanvas.com/yrzdf
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