after the spin coating of the PS-b-P4VP solution on Si wafers, they were put into a covered glass petri dish for Dioxane vapor solvent annealing for a period, and dried under ambient temperature controlled by the Air Conditioner in lab. After the surface reconstruction in Ethanol, i found out there are some small pores around 20-30 nm in regular array under both SEM and AFM. however, there are also some undesired 200-300 nm pores.
According the the SEM image, inside this pores, there are still some desired 20-30 nm pores present. These large pores look like some relatively large circular droplets condensed on polymer thin film, so it give a pressure to the surface of polymer thin film.
So would it be the problem of water droplets condensed during the solvent annealing ?
Make sure the wafer is on hydrophilic properties rather than hydrophobic to facilitate self-assembly process of the colloidal molecules going well.
Might also be beneficial to dry out the wafers under a negative pressure. I saw similar problems while working on thin polymer coatings.
You can use the preparing sample procidure of this artical (J. Phys. Chem. C 2010, 114, 3874–3882) may help you
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