Hi,
I have obtained inverse opals with metallic nano particles. The photonic band gap showed by them were different from the expected value. What may be the reason for their deviation from the predicted value. Hope someone can help me with valuable information.
Well, without seeing any data or any idea of the structure here are some suggestions of things to look for.
If you have a simulation tool you may be able to vary the parameters of the simulation to get a feel for what you observed as trends in the simulation is similar to what you see in experiment.
1) There may be shrinkage or expansion may give you a different periodicity than expected. That would shift the band gap.
2) You are dealing with real materials. The absorption loss of the material may be different than that of the bulk material parameter that might have been used in calculating your expected band gap. usually the real material will be lossy compared to the ideal material.
3) The structure may have a different shape than what what assumed in the original assumptions.
Since you have metallic particles the mean free path of the electron and structure of the material as well as the shape may all influence the plasmonic aspects and you may have a strong resonances. Depending on the spacing the coupling between particles may have an influence.
Hi John Muth,thank you so much for your valuable observations regarding this issue. Is it possible for you to provide some references regarding this observation.Regards
For a small shift of the band gap, there is a good chance that the refractive index in the structure and in your simulation don't exactly match, so another suggestion would be to measure the refractive index of the material on a thin film and then input the value in your simulation. I have found this to be most important in getting the simulation to match exactly the measured reflectivity for 1D photonic crystals.
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