Selective solvent crazing is proposed as a novel method for depth profiling and obtaining three-dimensional information by AFM on the microphase morphology in ultrathin polystyrene/poly-(methyl methacrylate) (P(S-b-MMA)) diblock copolymer films on silicon substrate. To remove selectively one of the blocks, chain scission must be achieved within this block. Therefore, a proper chosen solvent has to cause selective swelling combined with crazing. Both effects depend on differences in the solubility parameters of the polymers relative to the solvent. As a complementary contrasting procedure for the P(S-b-MMA) diblock copolymer system, plasma etching, which preferentially degrades PMMA, is used. For the same system a solvent crazing of the PS block is proposed with cyclohexane as a crazing agent. The novel procedure gets of special importance if the solvent-dependent morphology of spin-cast ultrathin diblock copolymer film can be inverted, e.g., if PMMA islands in a PS matrix spin-cast from toluene solution are inverted to PS islands in a PMMA matrix spin-cast from methyl ethyl ketone (MEK) solution.
Gourianova, Svetlana, Jürgen Fuhrmann