You should be more precise than this :) What exactly do you want to be helped with ?

aWell, I am new to ellipsometry and had grown SnS films on glass substrates to find the refractive index using Swanpoel method. This requires fringes in the transmission spectra. Unfortunately out of 8 samples I did not get fringes in 5. I was advised to go for ellipsometry. 

I got ellipsometry data of the samples for fixed theta and variable lambda. After studying literature, I realized that I need to know the substrates refractive index. I did data analysis and found refractive index for glass substrate using ellipsometry data. Now in case of film+substrate, I tried my hand on data analysis and wrote a code (wrote in gambas). The best MSE I am getting is 0.6 and the fit ofcourse isnt good.

I need assistance for data analysis and get better fit to my data. Using the 3 samples for which I am getting fringes, refractive index fits Sellimeir model.

Hello,

So in order to get a better fit, it is usually better to try multple theta angles.

Also, the goodness of the fit depends heavily on the model used (I don't know about SnS, but maybe you can find a start of a model for this material). Also, If the material is not very transparent, you need to take into account the absorption as well. To finish, you also need to make sure that you know very accurately the thickness of your thin film, as it has a large impact on your ellipsometric data.

I hope this helps,

Sebastien

for instance : you could start your fitting using the parameters measured in this publication : http://iopscience.iop.org/article/10.1088/0268-1242/4/5/009/pdf

Thanks for you input. I have tried most of your suggestions. I dropped a email on you "ca" account. Please respond.

How exactly the thickness can be estimated from the transmittance data? Gone through few articles but none works out in my case. I don't have any fringes in my spectrum (it is Zinc tin oxide on glass substrate: 94% transparent in the region 400-1100nm). Also, I want to extract the n and k values at each lambda. I tried using online resource called PUMA but unfortunately the results were uncertain. Can anyone help me out in this?

Dear Arun Palakkandy,

The material SnS is absorbing in the UV-VIS range. You should try to measure it in the NIR wavelength range (above 800 nm) to have the interference fringes necessary to obtain the thin film thickness. In the NIR range, the refractive index of SnS is around ~4, and the extinction is well below 0.5.

Best,

Peter