| dc.description.abstract | We have demonstrated the phase behavior in blend films, which were prepared by blending a symmetric weakly-segregated, polystyrene-block-poly (methyl methacrylate), (PS-b-PMMA), block copolymer with a homopolystyrene of comparable molecular weight (hPS) at the volume ratio which can form perforated layer structure. Film thickness was controlled by the polymer concentrations and spin rates. After film deposition by spin coating, the films were annealed at 230 or 270 °C. The thin-film structures were investigated in depth by using optical microscopy (OM), scanning electron microscope (SEM), grazing-incidence small-angle X-ray scattering (GISAXS), grazing incidence X-ray reflectivity (XRR), and Neutron Reflectivity (NR).
It can be observed a slow kinetic structure changes within 1 hour of annealing at 230 °C by in-situ GISAXS measurement, and the equilibrium structure is not reached after the temperature drops to room temperature, while the structure no longer changes after annealing at 270 °C for 10 minutes. For GISAXS data, the quantitative analysis of truncation rods demonstrates that the inter-perforation distance was approximately 37~40 nm. The inter-perforation distance is insensitive to the annealing temperatures, 230 and 270 °C. The analysis of GISAXS in the q⊥ direction shows that the perforated layer structure is mainly an ABC stack structure. From the analysis of angle-dependent GISAXS, it can be observed that the thick film annealed at 270 °C is more ordered than that at 230 °C, while the thin film has a mixed structure of vertical and horizontal perforated layers. XRR and NR offer structural details along the normal direction of the substrate. For thin films, XRR curves only display high-frequency fringes, which correspond to film thickness. low-frequency fringes associated with inter-layer spacing are absent from the XRR curves. The absence of low-frequency fringes is due to low contrast in SLD between PS and PMMA under X-rays. For thick films, the trend is the opposite. The reason is that detecting the high-frequency fringes of thick films is beyond the instrument resolution. For PS-b-PMMA/dPS blend films, NR curves display two series of fringes. High-frequency fringes correspond to the film thickness and low-frequency fringes are associated with the perforated layers. The presence of the low-frequency fringes is because dPS has a high SLD contrast to the hydrogenated chains. Quantitative analysis of XRR spectra and model fitting of NR spectra demonstrate that the inter-layer spacing of perforated layers was approximately 27~32 nm. | en_US |