I'm trying to spin-coat PMMA solutions (doped or not with various amount of gold salt) on glass substrates (1,5 cm^2).
The PMMA was used as received (Aldrich, Mw=150000 by GPC) and dissolve in acetone in an ultrasonic bath.
Up to now I've been trying concentrations ranging between 50 to 200 mg/mL of PMMA and speed between 1000 and 6000 rpm (spinning duration 40 s). I obtained some films with a thickness above 2 microns but the surface roughness is terrible! (300-400 nm).
Can someone help me finding the right parameters to fabricate nice flat films?
By the way, I'm also confused about the importance of spinning acceleration, it seems for me that it has no effect, is it always the case?
Thanks!
The effect of varying concentration and spin speed on the thickness of spin-coated poly(methyl methacrylate), i.e. PMMA, or polystyrene (PS) films can be found examined at: D.B. Hall, P. Underhill, J.M. Torkelson, "Spin coating of thin and ultrathin polymer films", Polymer Engineering & Science, 38(12) 1998, 2039-2045.
http://onlinelibrary.wiley.com/doi/10.1002/pen.10373/abstract
Try spin coating a solution made with a less volatile solvent. This may help with reducing the roughness.
Thank you Honglai for this data.
Philip, indeed the boiling of acetone, which is 56°C, is very low, but I'm trying to make thick films (1 to 4 mcs). And all the other solvents compatible with PMMA I know (Toluene, chlorobenzene, anisole) have a boiling point higher than 100 °C and are not particularly friendly. Would you know another solvent for PMMA that has a boiling point lets say around 90°C. So I might have a good compromise between thickness and roughness?
Regards,
We have found toluene to be the best solvent for PMMA. If the spin coater is in a fumehood the use of toluene should be no problem. Otherwise you could try THF or an ethanol/water mix though both aren't as good as dissolving the PMMA.
Please find attached file. Go through below links. These articles might be helpful.
http://onlinelibrary.wiley.com/doi/10.1002/app.43532/full
http://www.sciencedirect.com/science/article/pii/S0032386116301227
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