I am trying to synthesize MoS2 thin film on a glass substrate using drop casting method but I am getting the "coffee ring" effect on the substrate. How do I get rid of the rings and instead get uniform layers? I have tried spin coating but the viscosity of my solution is very low so, even after 30 layers, you can hardly see some flakes. Drop casting is my best bet but i just need to get rid of the coffee rings. Any tips/suggestions?
@Shrey Jain
The best way to coat your diluted solution on a substrate is to use a blade coating or bar coating. The drop casting films are always nonnon-uniform any way. It is easy and cheap way to use a bar coating.
The surface needs to be of the same molecular characteristic, lipophilics and hydrophilics together will not provide the spreading. A base coating will work!
The surface needs to be of the same molecular characteristic, lipophilics and hydrophilics together will not provide the spreading. A supportive base coating will work!
Riaz A. Khan I am using a glass substrate. What kind of coating would you suggest?
Shujie Li Should I heat the substrate while dispensing the drop? I heat the substrate after dispensing the solution.
Xuhua Wang My solution has very low viscosity. Also I dont have access to a blade or bar coating apparatus.
Shrey Jain Before preheating the substrate, keep in mind the boiling point of the drop-casted solution. Also, for low viscosity solution, spin coating is not a preferred approach instead you can try bar coating.
@Shrey Jain,
U can make your own using a flat blade tool or get a bar to coat a film. It only costs less than £10 or dollars. The following is an example
https://youtu.be/eA5pxqCN37E
Dear Shery Jain, for drop casting better to put your glass substrate around 60 degrees while dropping the MoS2 ink. Also if possible try to use a small size substrate. Additionally, you can try dip coating and I think you can achieve the required thickness by controlling the time. Finally, if you are using sonication for MoS2 ink exfoliation and dispersion use can try higher concentration or change your solvent.. Good Luck!
Shrey Jain did you overcome this problem? if yes then please let us know how?
I am facing same problem of coffee ring effect while depositing a thin film on platinum coated silicon substrate using dip coating method. How can I overcome this problem?
Clean the glass substrate properly with distilled water, acetone and iso-propanol and heat the glass substrate before deposition
Thanks. I am using platinum coated silicon substrate. Can I heat it before deposition?
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