Wall thickness and core radius determination in surfactant templated silica thin films using GISAXS and X-ray reflectivity

– X-ray reflectometry and GISAXS (grazing angle small angle scattering) are combined to investigate the morphology and structural parameters of a surfactant templated 2D hexagonal thin-film silica mesophase. It is shown that X-ray reflectivity measurements contain invaluable information about the radius of the cylindrical rods and the distance between their cores. The reflectivity data are analyzed using a model of the electron density and combined with GISAXS measurements to derive the silica wall thickness. Introduction. – Supramolecular-templating approach pioneered by Mobil researchers [1] uses surfactants to self-assemble inorganic precursors, such as that of silica, into precise arrangements of inorganic and organic constituents on the 1–50 nm length scale. Over the last 5 years, their synthesis has been adapted to the fabrication of supported inorganic mesoporous thin films using simple evaporation-induced self-assembly (EISA) [2] procedures such as dip-coating [3–7] and spin-coating [2, 8, 9]. Supported mesoporous inorganic thin-films are important for their applications in membranes [6], sensors [10, 11], photonics [12, 13], low dielectric constant insulators [14–17] and fluidic devices. Films with various morphologies: lamellar [3,18], hexagonal [3,4,7], cubic [3–5,19], 3D-hexagonal [3,5,20] have been fabricated, and techniques such as X-ray diffraction (XRD) [3, 4, 7], GISAXS [7, 9, 20, 21], scanning electron microscopy (SEM) [3], transmission electron microscopy (TEM) [3, 4, 20], atomic force microscopy (AFM) used to derive morphological and structural information. The structural dimensions of the organic and the inorganic phase dictate the final material properties such as mechanical strength, refractive index, dielectric constant, pore size, and surface area. Surface acoustic wave techniques combined with nitrogen adsorption [22, 23] have been used to characterize the pore size [3, 4] and in combination with X-ray data used to calculate the