If we spin coat ZnO nanoparticle on glass substrate and find the refractive index and extinction coefficient through ellipsometry, is that the complex refractive index of ZnO nanoparticle (assuming they are almost the same size), or is it the Effective refractive index of ZnO nanoparticle dispersed in air medium?
If it is not the right way to find the complex refractive index of a nanoparticle through ellipsometry of the spin coated layer, may I please know the right way of obtaining it?
Dear Vincent,
As you suspect, ellipsometry will give you the effective refractive index of the ZnO dispersed in air or the dried matrix that was diluted in you spin coating solution.
Then you should "separate" by modeling the optical properties of the nanoparticles from the one of the matrix to get what you look for.
Thank you for your kind reply Dr. Michel Stchakovsky. Can you please share any article which has done likewise?
Dear Vincent,
first you have to make sure that effective medium theory (EMT) can be applied and this will depend on the particle size which needs to be much smaller than the wavlength of light. Smaller means that volume scattering can be negelcted. One way is to check the aspect of your sample. If it looks like a mirror no problem if it looks milky most probably EMT will not be enough.
Assuming that EMT can be applied you can start by the simplest formula summing the polarizability of each material (this only applies to molecules or very very small particles). Then you can also start refining the model taken into the geometry of your particles. As examples, Maxwell Garnet, Bruggeman and Looyenga models can be used.
You will find many papers on porous silicon and EMT. Basically you can replace the dielectric function of Si by the one of ZnO. One remark of course classical EMT does not account for quantum confinement that may arise in a few nanometers size particles.
About EMT: D. Bergman Phys. Rep. C 43 (9) (1978) 377
About EMT applied to porous silicon: http://www.sciencedirect.com/science/article/pii/S016757299600012X
:
After coating, Effective dielectric constant of composite changed which changes the polarisability expression and resonance position accordingly.
Pls follow the link
http://link.springer.com/article/10.1007%2Fs11468-014-9677-4
Thank you very much, Professor Gilles Lerondel and Nilesh Kumar Pathak.
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