Ellipsometry- why is UV better than Visible light?

[lcr2139]

Hello,

I was wondering why UV ellipsometry is better than visible ellipsometry?

 

[Andy Resnick]

Better for what?

 

[lcr2139]

I meant, for certain materials, it is better to use UV light source to measure thin film thickness, and sometimes it is better to use a visible or NIR light source. Can someone please give me a couple of examples of materials that are determined using UV, VIS, and NIR? Why is it good to have the whole UV-VIS-NIR spectrum in an ellipsometer?

 

[quackyneudle]

If you only want to measure the thickness of a film, I believe that a single color i.e. laser is good enough as long as the medium has normal dispersion at that wavelength (negligible absorption). But, if you have access to a broader spectrum you can do spectroscopic ellipsometry, which allows one to more fully characterize a sample. For example, you can measure an absorption spectrum in conjuction with ellipsometry, etc. See this article https://en.wikipedia.org/wiki/Ellipsometry

The subection on single-wavelength vs spectroscopic ellipsometry directly addresses your question.