Spin coating of very thin polymer films

Very thin films of natural rubber, polystyrene, and poly(methylmethacrylate) have been spun‐cast on silicon wafers from dilute solutions of toluene and cyclohexane. Layers were uniform across the wafers, ranging from 0.5 to 170 nm, as measured by ellipsometry. Their average thickness e increased with solution concentration and decreased with rotational rate w. Changing the volume of the solution pipetted onto the wafers did not affect the final thickness, whereas changing the solvent did. The previously reported empirical relation for much thicker films, e α ω−1/2, held over the range investigated here.