MORPHOLOGICAL-STUDIES OF SPIN-COATED FILMS OF POLY(STYRENE-BLOCK-METHYL METHACRYLATE) COPOLYMERS BY ATOMIC-FORCE MICROSCOPY

The surface structure of very thin (15-20 nm) spin-coated films of a symmetrical poly(styrene-b-methyl-methacrylate) block copolymer on silicon and mica is analyzed by atomic force microscopy (AFM). The films show a surface corrugation of a very regular approximately 100 nm lateral periodicity and approximately 6-8 nm amplitude. Film thickness is measured by AFM at induced film defects and checked by ellipsometry. XPS shows that both blocks are at the film surface. Selective degradation of the methyl methacrylate block is used for contrast enhancement and allows to assign poly(styrene) to the elevated surface regions and poly(methyl methacrylate) to the substrate/film interface. Friction interactions of the AFM tip with the film surface may be used to induce high orientational ordering of the morphological pattern perpendicular to the fast scan direction.