I was wondering given the elliptical shape of ZnO nanoparticles, if they are spin coated on a glass slide, would it make it bi-refringent? The spectrum of light i am working on is NIR - 800-900 nm.
Thanks
Dear Yash,
there are some papers available dealing with non spherical nano particles and birefringence is discussed therein. However these sample systems exhibit quite (parallel) aligned nano particles, so a non-isotropic system is set up, which is a prerequistite for birefringence.
I do not know whether via spin coating a sufficient overall or (at least) local alignment of NP axis can be achieved. I assume that is not the case.
If birefringence shows up it will be restricted to the NP coverage and not be extended to the glass substrate.
Since ZnO is wuzwite or hexagonal structure so it will make birefringent because of anisotropic behaviour, whatever the glass substrate is used for film deposition via a spin coater or spray pyrolysis technique. By using optical microscopy you can observe birefringent characteristics.
But even though the nano particles are birefingent themselves (via internal birefringence or via shape) there is a need for alignment of these NPs in oder to get macrosopic birefringence of the NP coating. Does the the spin coating process align the NPs automatically (at least to some degree)? Could the elliptical cross sections help in alignment during flow of NP coating material?
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