Analysis of Depth-dependence and Orientation Behavior of Micro-phase Separated Structure of Block Copolymer Thin Films Investigated with GISAXS Measurement Utilizing Low Energy X-rays

In this review, we demonstrated grazing-incidence small-angle X-ray scattering (GISAXS) measurement with tender X-ray to achieve depth-resolved structure analysis of block copolymer systems, polystyrene-b-poly (2-vinylpyridine)(S2VP) and poly (methyl methacrylate)-b-poly (n-butyl acrylate) thin films (approximately 300 - 400 nm in thick). In the case of using tender X-rays, the penetration depth of X-rays in the vicinity of critical angle of total reflection becomes gentle as compared to the case of using hard X-rays. Herein, X-ray energies of 2.40 keV and 4.36 keV were employed to conduct depth-resolved structure analysis. The experimental full width at half maximum (FWHM) magnitudes of a diffraction spot was investigated to estimate the penetration depth. The incident angle dependence of experimental FWHM magnitudes indicated the same tendency as the FWHM values calculated with Laue function considering attenuation decay, meaning that the penetration depth was controlled by varying incident angles. Depth-resolved structure analysis revealed that in the case of the completely oriented thin film, micro-phase separated structures slightly deformed along the depth direction in the inside of the thin film and the deformation gradually relaxed near the surface.