Hey, Guys!
I am an undergrad and currently working on developing fluorescent samples for a prism coupling experiment. The idea is to spin cast Alq3 in 2ml Chloroform on glass slides. Under laser excitation, I notice that certain spots on the film glow brighter in comparison to other areas. The spots I guess indicate material aggregation. I am open to suggestions on how to overcome this problem.
At present, I plan to use a more viscous solution of Alq3 by adding 2 ml of IPA to the original solution as Chloroform and IPA are miscible and IPA has higher viscosity. I was also suggested to sonicate the solution for better dispersion. Increasing spin rate does not do any better beyond a point.
Hello, I would suggest you the same as someone already pointed you out; try sonicating in pulsated mode with a sonicating microtip, so you won´t evaporate your solvent.
Do you have any other solvent with higher boiling point than CHCl3? Maybe it is evaporating very fast when spinning, you can avoid that with another solvent. I hope it can help
Best regards
The most important consideration in spin coating is cleanliness of the substrate - your 'spots' are likely to be particulate contamination. All liquids must be filtered to better than 0.2 um (or 0.02 um for some applications). Work under Class 100 conditions, if possible.
Solvent boiling and thermal fluctuation is a given with sonication. See:
June 20th, 2013 Ultrasound, cavitation, and the singing kettle http://tinyurl.com/olueohz
Hi, Please consider following key points to increase the uniformity of film using spin coating;
In addition to the above said I would recommend using chlorobenzene or dichlorobenzene (preferably distilled) instead of chloroform. If it will not help try additionally fine filtering through syringe of the solution and playing with different speed rates. It depends).
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