I have prepared the solution for CZTS deposition using ethanol +DI water. But after heating the coated sample at high temperature, bubble spots are coming and thus the uniformity of thin layer is not present. How to remove these bubble formation? Is there any binder to do so, or any other process to get uniform thin film?
Dear Gautam,
First Check the cleaning of your substrate. clean your substrate with UV or plasma cleaning and then do the coating. After first coating bake the film at low temperature around 130°C for 5 minutes and then again spin coat follow this procedure until you achieved the desire thickness. Also put the low heating rate in the final annealing of the film.
Dear Gautam,
Thin uniform film preparation using spin coating depends on many factors that are to be optimized. When you are using ethanol and deionized water as solvent, I hope you have dispersed the precursor material uniformly using ultra sonicator. Another factor is viscosity of the medium as the forces that spread the materials are to be balanced for uniformity of the film. Finally, please check the rpm and optimize it. Pl. also ensure that the chemical route ( if used for material preparation does not involve nucleation and growth step at the same temperature.
Another factor that I would add to the comments of Bajpai is the substrate cleaning and the substrate-CZTS lattice matching issues, which may have important effect on what you experienced during deposition process.
Dear Gautam,
in my opinion you still have residual solvent in your material. You can try a pre-bake step at low temperature (around 100°C) and/or put your sample in vacuum to eliminate the rest of water and ethanol still present in your layer after spin coating step and proceed at high temperature.
The point is the solvent with low molecualr weight but enough viscosity, generally we used 2-methoxyethanol, although it has some toxity but it is the best currently (even better than DMSO).
Dear Gautam,
First Check the cleaning of your substrate. clean your substrate with UV or plasma cleaning and then do the coating. After first coating bake the film at low temperature around 130°C for 5 minutes and then again spin coat follow this procedure until you achieved the desire thickness. Also put the low heating rate in the final annealing of the film.
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