CZTS film remains stoichiometric up to 400C.However, the composition of the thin film becomes Zn-poor above 450 C because Zn vaporizes at the elevated temperatures.This leads to the loss of zinc.It can be compensated by spraying Zn and S vapors. But then the sulphur vapours may oxidize.In order to avoid it, CZTS films are taken out of the deposition chamber and are exposed to the atmosphere before sulphurization is performed to grow thin CZTS polycrystalline thin films. Moisture gets adsorbed on the surface and prohibits oxidation of S. The adsorbed moisture later leaves during annealing.This, IN LINE, sulphurization prevents oxidation.JIMBO ET AL employed this method with sputtered CZTS precursor films to prevent oxidation.
Apart from sulphurization, is it any other way to grow high grain during high temperature annealing? Should i do vacuum evaporation? Up to 350 C CZTS films remain black and give all the possible peaks in the XRD. But when i go beyond 350 C , it will be completely white.
Dear Prashant,
In our previous studies, we have annealed spray pyrolyzed CuInS2 films by both conventionally and rapid thermal annealing processes under vacuum without any reactive gases. Conventional annealing means the low heating rate and long process time while rapid thermal annealing means the fast heating rate and short process time. In this study, all the temperatures between 400 and 680 C. In terms of the oxygen content of the resultant films, conventional heating is more beneficial than rapid thermal annealing. Hence, I can suggest you apply low heating rate and long process time. However, you should be sure that without any reactive gases it is not very easy to obtain micron scale grains. In reactive annealing (sulfurization or selenization) partial pressure of the sulphur or selenium gases accelerates the crystal growth.
If you like to see the mentioned paper, you explore it from the following link.
All the best.
Article Conventional and rapid thermal annealing of spray pyrolyzed ...
Any reason, so are you going beyond 350 C? If you want to go higher temperature, you should try under vacuum or rapid thermal annealing.
Dear Erkan,
Thank you for your reply and sharing paper. I can't do rapid thermal or sulfurization/selenization process due to the limited availability of resources in my lab.
Hence, as per your suggestions, I have to go for conventional heating in order to achieve denser micron size grains. I will E-mail you when I will start my next phase of work.
Thanks again.
Kind Regards,
Prashant
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