GO aqueous solution requires a high concentration to form a film. In addition, spin coating results in a small amount of GO solution, and the amount of GO is too small to form a film.

Thanks for your reply, I think spin coating on a polymer substrate such as PET is relatively easy because plasma cleaning can change its hydrophilicity well, which is important for spin coating. However, this method is not very effective on silicon wafers, and I feel that silicon wafers need more complex treatment to have good spin-coating results.