Using UV - Vis spectrum, we calculate optical energy band gap. What is the necessity of calculating refractive index and extinction coefficient of a thin film? What are the applications concerning these two parameters?
When modeling photolithographic semiconductor processes n and k are necessary to understand how images form in photoresist films. These images become the patterns that make up the device. In order to manufacture modern semiconductors, lithographic process models are required, which makes the refractive index and extinction coefficient a requirement for manufacturing. This is just one application, there are many others. Is this what you are looking for?
Thank you Lawrence S Melvin. I am looking some other different answer related to my question. Starting from transmittance spectrum, i have calculated both refractive index and extinction coefficient. I do not know what to explain about these two graphs.
The refractive index and absorption are fundamental to being able to build photonic devices. For example if you want to design a waveguide you need to know the refractive index and thickness of the layer and the absorption is hopefully low for the wavelength you want to use the waveguide. If you want to make a photodetector it can be useful to know the parameters, or for other types of sensors where you may want to know how light is absorbed. If you know the refractive index and absorption of the material it is often useful in process control so you can determine the thickness of the deposited film.
To get the refractive index and absorption from just the transmission spectrum can be kind of tricky. If you want to extract the band gap energy it can also be tricky if are trying to get a very precise answer. On the other hand transmission measurements are quick, reproducible and convenient.
Often ellipsometry is used because the technique gathers more information i.e. the phase of the reflected light in addition to the magnitude of the signal.
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