Dear Aeree,

I am not an expert in spin coating. However, from the visible Patterns it is easy to assess that the particles are not forming a stable Dispersion. In order to produce a uniform film, you have to reduce the tendency to coagulate, i.e. you Need a high zeta potential. May I suggest you to find out the appropriate pH for high electrophoretic mobility and try again.

I hope this helps.

Thank you Mr Chauhan! I didnt consider pH to disperse particles uniformly.

I agree with your opinion and I thought this might be because of failed dispersion. Because solution looks white but I saw particles dispersed well. it is

Thank you for your response Mr. Kumar. 

My solution does not undergo sol-gel process. It is just particles with solvent.

In this situation, MEA that used as controller of pH of condensation reaction does work?

Dear Aeree,

If you are following a standard protocol it might be possible to do a quick literature review on the subject and find out what the proper pH range would be. Else, you can find out the zeta potential using a DLS coupled zeta sizer equipment, if you have access to one.

In my experience slightly acidic pH works best for oxide powders.

Regards

I'm not a spin-coating expert as well, but it seems that your solution is too viscous and perhaps the wettability of silicon is too low. You could consider:

1. some compatible additive to reduce viscosity

2. some silicon surface pre-treatment to increase wettability with your chosen solution

3. heating the substrate during spin-coating (if possible)

Of course, all above are indicative routes that requires some more study and effort to make them affordable to your specific needs